JPH10242621A - Smoothed printed wiring board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smooth and stabilize the circuit forming surface of a board, eliminating the step between its conductor and insulation portions, by performing the laminate bonding press of a copper foil and a prepreg to form its circuit, and by applying thereafter to them a heat treatment before their smoothing press to make the smoothness of its circuit forming surface not larger than a specific value. SOLUTION: Before completing the set-up of a laminate bonding press process using a lamination jig. superimposing a copper foil 2 on a prepreg 1, a mold releasing aluminum sheet 3a is superimposed on the side of the prepreg 1 to sandwich the intermediate between a stainless steel sheet 3b and a cushion sheet 3a upper and lower sidewise. Then, before the smoothing press of these layers, their laminate bonding press condition is set according to the resin used in the prepreg 1. When their laminate bonding press condition is set to one hour at 150 deg.C, their laminate bonding press is performed as applying to them the heat treatment of 80-130 deg.C in press temperature and 20-70 minutes in press time to make the smoothness of the circuit forming surface of a printed board not larger than 5μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a smooth printed wiring board and a method of manufacturing the same, and more particularly, to a smooth printed wiring board having a smooth surface on the circuit forming surface side of the printed wiring board and a method of manufacturing the same.

[0002]

2. Description of the Related Art Smooth printed wiring boards are used in devices having movable parts such as automatic air conditioner automatic heating / cooling changeover switches, rotary switches and slide switches, and contact switching mechanisms in order to simplify complicated structures. I have. Such a smooth printed wiring board requires, for example, a movable part to replace the photocoupler mechanism of a mouse for a personal computer that requires a durable life of tens of millions of times or more. There is a demand for stable and low-cost products.

Conventionally, as a method of manufacturing a smooth printed wiring board, a copper foil is laminated and adhered on a prepreg, a circuit is formed, a conductive circuit portion is plated with gold, further sandwiched between mirror-surface stainless steel plates, and heated under pressure to heat the substrate surface. A method of manufacturing a smooth printed wiring board having excellent smoothness is known (Japanese Patent Publication
No. 6-09542).

[0004]

However, in the conventional method of manufacturing a smooth printed wiring board, there is a problem that a step is easily left between the conductor portion and the insulating portion on the surface of the printed wiring board, and the smoothness is not sufficient. Was. Particularly, when a plurality of smooth printed wiring boards are manufactured at the same time, there is a problem that uniform smoothness cannot be obtained between the respective smooth printed wiring boards.

[0005] In addition, there is a problem that, when trying to obtain uniform surface smoothness, resin fogging or the like occurs in the wiring portion of the circuit board.

[0006] When such a problem occurs, for example, when a printed wiring board having a step in a conductor portion and an insulating portion is used together with a sliding brush, the brush is rapidly consumed.
When the brush jumps due to the step when sliding,
In addition, there is a problem that stable and highly reliable characteristics cannot be obtained due to resin fogging or the like.

[0007] Further, as switches become more sophisticated, multilayer smooth printed wiring boards are required, but a smooth printed wiring board using a double-sided printed wiring board can obtain uniform surface smoothness. There was a problem that can not be.

SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and in the case of manufacturing a smooth printed wiring board, especially in the case of manufacturing a plurality of sheets at the same time, a step is formed between the conductor portion and the insulating portion. It is an object of the present invention to provide a smooth printed wiring board capable of obtaining a stable and highly reliable characteristic having a smooth circuit formation surface and a method of manufacturing the same, and a method of manufacturing a double-sided smooth printed wiring board.

[0009]

A smooth printed wiring board according to the present invention is a smooth printed wiring board having a smooth circuit forming surface on the printed wiring board. The circuit is formed by laminating and pressing a copper foil and a prepreg. After that, by performing a heat treatment before the smooth pressing, the smoothness of the circuit forming surface is reduced to 5 μm or less.

The method for manufacturing a smooth printed wiring board according to the present invention is a method for manufacturing a smooth printed wiring board having a lamination adhesive pressing step of stacking and pressing at least one set of copper foil and prepreg, and a smooth pressing step after forming a circuit. The method is characterized in that a heat treatment step of heating the smooth printed wiring board is provided between the lamination bonding press step and the smooth press step.

Further, the heat treatment step is carried out under the heat treatment conditions in which the minimum adhesive strength in circuit formation is obtained and the smoothness of the circuit formation surface after the smooth press step is 5 μm or less. In addition, the heat treatment is performed under the condition that the smoothness of the circuit formation surface is 2 μm or less.

Further, in the case where a plurality of smooth printed wiring boards are simultaneously manufactured, the heat treatment step is performed under heat treatment conditions that make the thermal energy integrated amounts of the plurality of smooth printed wiring boards substantially equal before the smooth pressing step. And

[0013] In the method for manufacturing a multilayer smooth printed wiring board, the laminating and pressing step includes a step of pressing copper foils arranged on both sides of a plurality of prepregs having different degrees of curing.

In the above case, the plurality of prepregs are at least three prepregs, and the prepreg arranged on the copper foil side has a higher degree of curing than the prepreg arranged inside.

[0015] The lamination bonding press step is a step of laminating and pressing a copper foil on which at least one double-sided printed wiring board is laminated via a prepreg and arranged on both surfaces via a prepreg. There is a feature.

The method for manufacturing a metal plate-based smooth printed wiring board includes a smooth pressing step in which the double-sided printed wiring board is laminated and pressed with a metal plate via a prepreg, and the double-sided printed wiring board is formed of at least the above-mentioned. It is a three-sided prepreg, wherein the prepreg disposed on the copper foil side is a double-sided smooth printed wiring board obtained by a plurality of prepregs having a higher degree of curing than the prepreg disposed inside.

The smoothness of the circuit forming surface according to the present invention refers to the degree of the surface roughness of the entire circuit forming surface including the step region between the conductor portion surface and the insulating portion surface. It refers to the degree of surface roughness when the undulating surface is regarded as a straight line. Specifically, it refers to the difference between the minimum thickness and the maximum thickness of the circuit forming surface when scanning is performed within a range of ± 2 mm between the conductor and the insulating portion.

The fact that the minimum adhesive strength is obtained in the formation of a circuit means that the copper foil and the prepreg have an adhesive strength so as not to peel off during pattern formation or plating of a printed wiring board.

In the present invention, the degree of curing refers to the degree of crosslinking of the resin component constituting the adhesive of the prepreg, and the higher degree of curing means that the crosslinking is more advanced.

According to the present invention, there is provided a method for manufacturing a smooth printed wiring board, particularly when a plurality of printed wiring boards are manufactured at the same time. This was obtained as a result of pursuing conditions that enabled the following. In other words, in order to solve problems such as resin fogging and poor smoothness, 1) how to minimize the resin flow out of the work in the lamination bonding press process, and 2) how uniform curing of the adhesive in the heat treatment process. Secure the degree or 3)
In the smooth press process, it is important how to smooth the surface of the conductor and insulating resin and work under conditions that do not cause resin fogging. Therefore, the press working conditions and printing in the lamination adhesive press process and the smooth press process are important. This is based on the finding that optimization of the integrated amount of heat energy for a wiring board is the most important.

In addition, in the case of a double-sided smooth printed wiring board, since the steps of drilling through holes, copper plating and filling holes are added, the processing conditions in the lamination bonding press step and the heat treatment step become complicated. It has been found that a smooth printed wiring board can be manufactured even in a multilayer printed wiring board by adjusting the degree of hardening of a prepreg sandwiching two copper foils.

More specifically, the present invention provides a laminate adhesive press for a printed wiring board under a prepreg curing condition capable of securing a minimum adhesive strength that can withstand a circuit pattern formation and a plating process to be performed in a later step, and smoothing. Optimize heat energy integration by heat treatment before pressing.

In the case of a multilayer smooth printed wiring board,
A similar effect can be obtained by performing a laminated adhesive press using prepregs having different degrees of curing to form through-holes and the like to obtain a double-sided smooth printed wiring board, and then performing a heat treatment before the smoothing press. As a preferable form of the prepreg arrangement having different degrees of curing, a prepreg with advanced curing is arranged on the copper foil side, and a prepreg less cured than the prepreg on the copper foil side is arranged inside the prepreg. The layer pushes up the resin layer of the prepreg, thereby enabling smoothing. Even when a general double-sided printed wiring board is used as an inner layer, a smooth printed wiring board can be obtained by performing a heat treatment before the smoothing press.

Finally, in the smoothing press step, a smooth press is performed under conditions that allow more complete hardening and smoothing of the printed wiring board. As a result, the smoothness of the circuit formation surface of the printed wiring board can be reduced to 5 μm or less, and a device having highly reliable movable parts can be realized. Further, by providing the heat treatment step, the production yield is improved particularly when a plurality of smooth printed wiring boards are manufactured at the same time, and a smooth printed wiring board of stable quality can be obtained at low cost.

Further, in the method of manufacturing a smooth printed wiring board based on a metal plate, a smooth printed wiring board can be easily manufactured by using the above-mentioned double-sided smooth printed wiring board.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a printed wiring board according to the present invention will be described with reference to FIG. FIG. 1 is a flowchart showing the manufacturing process of the printed wiring board of the present invention. First, a prepreg 1, a copper foil 2, and a lamination jig 3 are prepared. Next, the prepreg 1 and the copper foil 2 are superimposed, set up using a laminating jig 3 such as a release aluminum plate or a cushion plate, and inserted between hot plates 4 of a hot press to perform a laminating adhesive press. At this time, if necessary, a plurality of prepregs and copper foils are overlapped and a laminating adhesive press is performed simultaneously under predetermined conditions.

The prepreg according to the present invention can be used as long as the base material is impregnated with a thermosetting resin. Examples of the substrate include paper, glass cloth, glass nonwoven fabric, polyester film, polyester nonwoven fabric, aromatic polyamide paper (Dupont product name, Nomex), or a combination thereof. Examples of the thermosetting resin include: Examples thereof include an epoxy resin, a phenol resin, a polyimide resin, an imide-modified epoxy resin, an aralkyl ether resin, a polyvinyl phenol resin, and a bismaleimide / triazine resin. Among them, in order to obtain a smoothness of 5 μm or less, preferably 2 μm or less through the heat treatment in the present invention, a prepreg using a glass nonwoven fabric as a base material and an epoxy resin as a thermosetting resin is particularly preferable.

The thickness of the prepreg is 0.05 to 0.40 mm.
It is preferable that the resin content in the glass prepreg is about 35% to 75% and 0.1 mm or
A prepreg having a thickness of about 0.2 mm can be suitably used. Further, a plurality of prepregs having such a thickness can be used in piles.

The copper foil according to the present invention is not particularly limited,
It is preferable to use a copper foil having a thickness of about 12 to 70 μm. For a two-sided smooth printed board, 5 to 1000
μm, preferably 10-600 μm, more preferably 18
Copper foil of ~ 400 µm thickness can be used.

In particular, in the case of a double-sided smooth printed board, it is preferable to use a plurality of prepregs in accordance with the thickness of the copper foil in order to obtain excellent smoothness, and specific examples are shown in Table 1. Show.

[0031]

[Table 1]

As an example of the setup in the lamination bonding press step using a lamination jig, the method shown in FIGS. 2 and 3, for example, can be mentioned. FIG. 2 is a diagram showing an example of a setup in the lamination bonding press step, and FIG. 3 is an example of a case where six units are stacked.
As shown in FIG. 2, the prepreg 1 and the copper foil 2 are overlapped, the release aluminum plate 3a is overlapped on the prepreg 1 side, and the upper and lower sides are sandwiched between the stainless steel plate 3b and the cushion plate 3c to complete the setup. Further, as shown in FIG. 3, the units can be stacked so that the prepreg 1, the copper foil 2, and the release aluminum plate 3a are always sandwiched by the stainless steel plates 3b, and a large number of units can be simultaneously laminated and pressed.

The lamination bonding press step is to bond the copper foil 2 and the prepreg 1 and to optimize the curing of the prepreg in order to easily form a circuit pattern and to improve the smoothness in the smooth pressing step. It is in. That is, if the prepreg is not sufficiently cured in the laminating and pressing step, the etching resistance and plating resistance at the time of forming a circuit pattern are inferior, and a resin fogging phenomenon or the like occurs in the smooth pressing step. On the other hand, if the prepreg hardens too much, the resin flow in the smooth pressing process becomes insufficient,
Smoothness of less than μm cannot be obtained. For this reason, it is necessary to set the optimal curing conditions to obtain a smoothness of 5 μm or less in the laminating adhesive pressing step and the smoothing pressing step. Specifically, in the lamination adhesive pressing step, it is preferable to set a pressing condition in which the amount of heat energy is smaller than the standard curing condition of the prepreg.

On the other hand, in the laminating and pressing step, when a plurality of units in which the prepreg and the copper foil are superimposed are laminated and bonded at the same time, the unit set at a position close to the hot plate of the hot press and the unit set at an intermediate position The amount of heat energy added differs depending on the stacking position of the unit. If the amount of heat energy is different, optimal curing cannot be obtained,
The smoothness of not more than μm, preferably not more than 2 μm cannot be obtained. Therefore, in the present invention, after the lamination bonding press step, the prepreg to which the copper foil is bonded is regarded as one unit, disassembled into a plurality of units, and each is subjected to a predetermined heat treatment. Thereafter, a conductor pattern is formed, and the process before the smooth press is completed.

The conductive pattern can be formed by any method such as a method using a dry film or a method by pattern printing.

In the heat treatment step according to the present invention, in order to make the smoothness after the smooth press step 5 μm or less, preferably 2 μm or less, the heat energy integrated amount of each of the printed wiring boards before the smooth press step is almost equal. Perform under conditions. Specifically, the conditions for laminating and pressing are set according to the resin used for the prepreg. For example about
A glass epoxy prepreg with a size of about 300 mm x about 500 mm, with standard curing conditions of 150 ° C for 1 hour, or
If the temperature is 130 ° C for 4 hours, the press temperature should be 80 to 13
0 ℃, press time (time after reaching set temperature) 20
Set to about 70 minutes. Even in this case, when a plurality of units are laminated and bonded at the same time, the amount of applied heat energy differs due to the difference in the respective stacking positions.

The specific relationship will be described with reference to FIG. FIG.
Shows the results of measuring the relationship between the set lamination bonding press conditions and the temperature and time in each unit. In FIG.
A is the measured temperature of the unit set closest to the hot plate of the hot press, C is the measured unit of the unit set farthest from the hot plate, and B is the measured temperature of the unit set at the intermediate position between A and C. It is a time relationship. As shown in FIG. 4, the temperature curve at the time of temperature decrease is sharper than that at the time of temperature rise.
In units set at positions A, B, and C,
The integrated thermal energy amount of the unit set at the position C is the smallest. The curing reaction of the prepreg is a chemical reaction, and the reaction speed follows the Arrhenius law. For example, the activation energy of the prepreg curing reaction is 20 to
Assuming 50 kcal / mol, increasing the curing temperature by 8-10 ° C doubles the curing speed. It also depends on the reaction time. Therefore, the heat treatment conditions according to the present invention are set in consideration of temperature and time. Specifically, it is preferable to make the accumulated heat energy amounts substantially the same by changing the time while keeping the temperature that is easy to set constant.
Whether or not the accumulated heat energy amounts are substantially the same can be determined by the smoothness after the smooth press step. In addition, even in the case where only one unit in which the prepreg and the copper foil are overlapped is subjected to the lamination bonding press in the lamination bonding pressing step, the smoothness after the smooth pressing step can be increased by performing the heat treatment.

Next, a noble metal plating for imparting sliding resistance is applied to the conductor pattern of the printed wiring board having substantially the same integrated thermal energy as necessary. The printed wiring board, a thermosetting resin plate, a prepreg, and a smoothing jig are set up, inserted between hot plates of a hot press, and subjected to a smooth press under conditions that the prepreg and the like are completely cured.
At this time, if necessary, a plurality of printed wiring boards are overlapped and a smooth press is performed simultaneously under predetermined conditions.

FIG. 5 shows an example of the setup in the smooth press step. The prepreg 1 and the thermosetting resin plate 3d are further arranged on the back surface of the printed wiring board 5 on which the circuit pattern is formed, sandwiched between stainless steel plates 3b, and smooth pressed by a hot press via the cushion plate 3c. The prepreg 1 may be omitted, or a thermoplastic resin plate or a metal plate may be used instead of the thermosetting resin plate 3d.

Also, by changing the setup method in the laminating adhesive pressing step and the smoothing pressing step to a method other than the above-mentioned method, the working efficiency and the smoothness can be improved. An example of such a setup will be described below. B) In the lamination bonding press process, the thermosetting resin plate 3d
At the same time, a semi-cured thermosetting resin sheet 6 is simultaneously arranged and set up, and a laminated adhesive press is performed. In a smooth press process, the printed wiring board 5 on which a circuit pattern is formed (hereinafter abbreviated as the printed wiring board 5) is formed. The smooth press is performed by the method described above. In this case, an etching apparatus for manufacturing a general printed wiring board can be used without requiring an etching apparatus dedicated to a thin substrate or an etching apparatus dedicated to a flexible substrate. Further, a smooth printed wiring board having good smoothness can be obtained without using a release aluminum plate. The flowchart and the setup method are shown in FIGS. 6 and 7, respectively. B) In the lamination bonding press step, a lamination bonding press and a smoothing press are performed in the same manner as a) except that two semi-cured thermosetting resin sheets 6 are used. In this case, a)
A smoother printed wiring board can be obtained. The thermosetting resin sheet 6 may be a glass cloth impregnated with a thermosetting resin. C) In the laminating adhesive pressing step, the laminating adhesive press and the smoothing press are performed in the same manner as in a) except that one or two prepregs 1 are used instead of the semi-cured thermosetting resin sheet 6. In this case, a general etching apparatus for manufacturing a printed wiring board can be used. D) In the lamination bonding press step, a lamination bonding press and a smooth press are performed in the same manner as in a) except that the semi-cured thermosetting resin sheet 6 and the prepreg 1 are used. In this case, a general etching apparatus for manufacturing a printed wiring board can be used. As described above, various combinations can be used from a soft sheet such as a prepreg, a thermosetting resin sheet, a thermosetting resin plate to a hard plate.

Thereafter, the printed wiring boards are taken out from the hot press, and a plurality of printed wiring boards are disassembled, and the required portions are manually machined with a drilling machine or automatically drilled with an NC drilling machine. Next,
Punching into a predetermined shape with a punching press or N
It is processed into a predetermined shape by a C contour processing machine or the like, and a smooth printed wiring board is completed.

Next, the double-sided smooth printed wiring board will be described. In the case of a double-sided smooth printed wiring board, since steps such as drilling of through holes, copper plating, and hole filling are added, the printed wiring board is subjected to a lamination bonding process and a heat treatment process so as to have characteristics that can withstand these processes. It is important to build. Also, in the case of a multilayer smooth printed wiring board or a metal-based smooth printed wiring board, a step of forming through-holes or the like is added as in the case of a double-sided smooth printed wiring board. The present invention is characterized in that such a double-sided smooth printed wiring board or the like is subjected to a lamination adhesive press using prepregs having different degrees of curing. A method for manufacturing a double-sided smooth printed wiring board will be described with reference to FIGS.

FIG. 9 shows an example of a case in which a laminate adhesive press is performed using prepregs 1a and 1b having different degrees of curing from the beginning. FIG. 10 is a cross-sectional view of the double-sided smooth printed wiring board in the manufacturing process along the Q route in FIG. 9, (a) after lamination and bonding press, (b) after NC drilling, and (c). Shows the section after filling the conductive paste holes, (d) shows the section after copper plating, (e) shows the section after pattern formation, and (f) shows the section after smooth pressing. First, prepregs 1a and 1b having different degrees of curing, copper foil 2, and laminating jig 3 are prepared. Next, prepregs 1a having a higher degree of curing than the prepregs 1b are arranged on both sides of the prepregs 1b, and copper foils 2 are overlapped on both sides of the three-layer prepregs to form a laminating jig 3 such as a release aluminum plate or a cushion plate. It sets up using it, inserts between the hot plates of a hot press, and performs a lamination adhesive press. At this time, if necessary, a plurality of prepregs and copper foils are overlapped and a laminating adhesive press is performed simultaneously under predetermined conditions. The prepreg 1a and the prepreg 1b are preferably different in the degree of curing between the prepreg 1a at 150 ° C. for 1 hour and the prepreg 1b at 150 ° C. for 3 hours. The conditions for the lamination bonding press were as follows: a press temperature of about 115 ° C, a press time (time after reaching the set temperature) of about 60 minutes, and a press pressure of 10 kg / cm.
^{About 2} is preferred.

Next, disassembly, heat treatment, and NC drilling are performed.
If necessary, a hole is filled after through-hole copper plating, or copper plating is performed after filling the hole without performing through-hole copper plating, and a pattern is formed by the above-described method. In the heat treatment, after the laminating adhesive pressing step is performed in the same manner as described above, the double-sided smooth printed boards are disassembled, and a predetermined heat treatment is performed so that the amounts of heat energy applied to the respective boards are equal as described above.

Hereinafter, the filling process will be described. The hole filling step includes, in detail, 1) filling of a filler 7 such as a conductive paste or insulating ink, 2) curing of the filler by heat or ultraviolet rays, and 3) surface preparation and polishing (FIG. 10).
(A) to (c)).

The conductive paste is composed of a conductive filler and a binder. As the conductive filler, a metal filler such as copper or silver powder or carbon can be used. Among them, a conductive paste suitable for the present invention includes a copper powder as a conductive filler, and a conductive paste using a non-solvent thermosetting epoxy resin as a binder. This is because the pattern density and the mounting density of the printed wiring board are increased, and the distance between the through-holes is reduced, so that ion migration, which has recently become a problem, can be suppressed. The copper powder is preferably spherical and has a particle size of 5 to 10 μm. The solvent-free thermosetting epoxy resin is particularly suitable for the present invention because it has a low viscosity and a small amount of volatile components required for the binder, and has excellent heat resistance and thermal shock resistance after curing. The conductive paste obtained from such a copper powder and a thermosetting epoxy resin binder has a low rate of change in resistance in a temperature cycle after curing, hot oil, and a solder reflow test, and a through-hole resistance per hole after curing. Is about 1 to 10 mΩ, and desirable characteristics can be obtained. Further, it is possible to prevent deformation and disconnection of the through-hole hole wall due to the pressing force in the subsequent smooth pressing step. Note that an antioxidant and a dispersant can be added to the conductive paste.

The insulating ink according to the present invention can be used either of a thermosetting type or an ultraviolet curable type. FIG. 9 shows a thermosetting insulating ink suitable for the present invention.
In the P path shown in the figure, the volume decrease due to heat curing is small, the hole can be filled neatly, excess ink on the copper foil surface can be easily removed by surface polishing, it has acid resistance and is suitable for ferric chloride solution or cupric chloride solution. It is heat-cured because it is not eroded, has acid resistance in the hole filling process and is not eroded by the copper sulfate plating solution, and has excellent adhesion to etching resist ink, dry film and liquid resist used for pattern formation in the later process. An epoxy resin is most suitable. The preferred viscosity is 150 to 350 Poise, and the preferred curing conditions are 100 to 130 ° C./30 to 60 minutes.

As the ultraviolet-curable insulating ink suitable for the present invention, any ink having a nonvolatile content of 100% and having the same properties as the above-mentioned thermosetting epoxy resin can be used. However, it is preferable that the ultraviolet curing can be carried out by a commonly used ultraviolet curing apparatus. As the curing conditions, for example, a high-pressure mercury lamp of 80 W / cm × 3 and a conveyor speed of 1 to 3 m / min are suitable. Similarly to the conductive paste, the insulating ink used for filling the holes can prevent deformation and disconnection of the wall of the through-hole due to the pressing force in the subsequent smooth pressing step.

A method of filling the conductive paste or the insulating ink will be described. 1) As the conductive paste, use a 80-120 mesh screen printing tetron or stainless steel printing plate.
Alternatively, the holes are filled in the holes by screen printing using a metal mask formed by drilling a 50-200 μm thick stainless steel plate by etching or the like. 2) Since the insulating ink for filling holes is only a resin component and does not contain a metal filler, it can be filled by a roll coater method.

In the case of a thermosetting insulating ink, the filling is cured by touch drying and preliminary curing, and the main curing is carried out in a subsequent smooth pressing step. Dry to the touch is 60 to 90 ℃ / 6
A time of about 0 minutes is preferable for pre-curing at about 100 to 120 ° C. for about 60 minutes to obtain smoothness. In the case of an ultraviolet curing type, it is completely cured by ultraviolet rays.

In the surface adjusting / polishing step which is the last of the hole filling step, the excess paste or ink on the surface of the copper foil is removed by polishing with a belt sander or a buff. Since the copper powder filler according to the present invention is harder than the silver powder filler, it is excellent in abrasiveness.

After the hole filling step, the copper plating step (FIG. 10)
(D)), a pattern forming step (FIG. 10 (e)), a smooth pressing step (FIG. 10 (f)), etc., to obtain a double-sided smooth printed board. The copper plating according to the present invention is preferably performed by a subtractive method. In this case, as a method of using electroless copper plating, there is a method in which a palladium catalyst is adsorbed for conductivity to perform electroless copper plating at 0.3 to 0.5 μm. Alternatively, methods that do not use electroless copper plating include palladium systems that do not use formaldehyde or chelating agents that are problematic in electroless copper plating, conductive polymer systems, carbon graphite systems,
Methods such as an ion exchange group system can be mentioned. With these methods, the inside of the hole wall is made conductive, and thereafter, electrolytic copper plating is performed for 25 to 30 μm to obtain a copper plating layer 8 (FIG. 10D). Thereafter, pattern formation is performed by the above-described method (FIG. 10E).

The smooth pressing step can be performed under the same pressing conditions as in the method shown in FIG. However, in the present invention, the prepreg 1b having a low degree of curing is present in the inner layer of the double-sided copper foil plate, and the resin layer of the prepreg 1b is smoothed by pushing up the resin layer of the prepreg 1a on the copper foil side in the smooth pressing step. (FIG. 10F). For this reason, it is preferable to provide the stainless steel plate 3b in contact with the double-sided copper foil plate.

Another method of manufacturing a double-sided smooth printed wiring board will be described with reference to FIGS. FIG.
Flow chart of a manufacturing process of a double-sided smooth printed wiring board in which the degree of cure of a prepreg disposed on a copper foil side can be made larger than the degree of cure of a prepreg disposed inside by two steps using a prepreg 1c having the same degree of cure. It is. FIG. 12 shows an arrangement diagram of the prepreg and the copper foil in the lamination bonding press step. In FIG. 11,
The steps after NC drilling are the same as in FIG. First, a prepreg 1c, a copper foil 2, and a lamination jig are prepared. These are set up and inserted between hot plates of a hot press to perform the first laminated adhesive press. By this lamination bonding press, the prepreg 1c becomes a prepreg 1d in which thermosetting has been advanced. Next, the disassembly is performed, and as shown in FIG. 12A, the printed wiring boards obtained by the first lamination bonding press are overlapped so as to sandwich the uncured prepreg 1c, and the setup and the lamination bonding press are performed again. 12
(B)). Even with such a method, the degree of cure of the prepreg 1d arranged on the copper foil side can be made larger than the degree of cure of the prepreg 1c arranged inside.

In this case, the lamination bonding press conditions for laminating the first copper foil and the prepreg 1c are as follows: a press temperature of about 110 ° C., a press time (time after reaching the set temperature) of about 30 minutes, The pressing pressure is preferably about 10 kg / cm ² , and the lamination adhesive pressing conditions for forming the prepreg into a three-layer structure include a pressing temperature of about 115 ° C and a pressing time (time after reaching the set temperature) of 60 minutes. And the pressing pressure is preferably about 10 kg / cm ² . Under such conditions, prepregs 1c and 1d having different degrees of curing can be obtained in the same manner as in the method of performing the lamination bonding press using prepregs 1a and 1b having different degrees of curing from the beginning. After the laminating and pressing step, a double-sided smooth printed wiring board can be manufactured in the same manner as in FIG.

The double-sided smooth printed wiring board manufactured by the method shown in FIG. 9 or FIG. 11 has the following features. 1) The conductive paste or the insulating ink is filled in the through-hole holes, and the deformation of the through-hole hole walls during the smooth pressing is very small. 2) When the conductive paste is filled in the through hole, or since the through hole is filled, the component can be mounted on the hole. 3) Even if the land diameter is reduced, the through hole is filled, so that the etchant does not enter the through hole during pattern formation (etching) and does not cause a problem on the hole wall. The density can be improved and the area of the printed wiring board can be reduced. 4) Since the through-hole is filled with the conductive paste or the insulating ink, the etchant does not enter the through-hole at the time of pattern formation (etching) and does not cause a defect on the hole wall. Absent. 5) Similarly, there is no flux residue in the through-hole in the component mounting process, and there is no corrosion of the through-hole wall, and a highly reliable mounted printed wiring board can be manufactured. 6) When the conductive paste is filled in the through hole, or since the through hole is filled, the through hole can be used for the purpose of heat dissipation.

Next, a method for manufacturing a double-sided smooth multilayer printed wiring board using the above-mentioned double-sided smooth printed wiring board or a commercially available double-sided printed wiring board as an inner layer board will be described with reference to FIGS. FIG. 13 shows an arrangement diagram of a double-sided printed wiring board and the like, a prepreg, and a copper foil in a lamination bonding press step. A double-sided smooth printed wiring board without noble metal plating or a commercially available double-sided printed wiring board without noble metal plating is used as the inner layer board 10 in the double-sided smooth printed wiring board produced by the method shown in FIG. 9 or FIG. Further, a copper foil 2 is set up on the outside, inserted between hot plates of a hot press and laminated and pressed, and dismantled and heat-treated in the same manner as the method shown in FIG.
Through an NC drilling step and the like, a double-sided smooth four-layer printed wiring board can be obtained. Incidentally, even if the surface of the commercially available double-sided printed wiring board is not smooth, the surface smoothness of the heat treatment step and the smoothing step of the present invention is 5 μm or less,
Preferably, a double-sided smooth printed wiring board of 2 μm or less can be obtained.

Further, a double-sided printed wiring board having a partly unsmoothed part is produced by the method of FIG. 9 or FIG. 11 using a thick copper foil of 75 or 100 μm as a four-layer printed wiring board.
By setting up with the method shown in FIG. 13 without noble metal plating, a double-sided smooth four-layer printed wiring board can be obtained.

By using a plurality of the above-mentioned double-sided smooth printed wiring boards, a multilayer printed wiring board having four or more layers can be manufactured. FIG. 14 shows an example of such a multilayer printed wiring board. FIG. 14 shows a double-sided smooth printed wiring board.
FIG. 14A is a cross-sectional view of a double-sided six-layer printed wiring board using two sheets, and FIG. 14A shows a state after the lamination bonding press step, and FIG. In this case, by setting up prepregs on both sides of the double-sided smooth printed wiring board, a double-sided smooth six-layer printed wiring board can be obtained in the same manner as the four-layer printed wiring board.

The double-sided multilayer smooth printed wiring board manufactured by the method shown in FIG. 13 or FIG. 14 has the following features. 1) The pretreatment of through-hole copper plating for desmear and etch back, which has been conventionally performed on a multilayer printed wiring board, becomes unnecessary. 2) Since the electrolytic copper plating is not performed on the through hole,
Through holes with a minimum drill diameter of 0.3mmφ and an aspect ratio of 3 can be formed. 3) Since the through-hole is filled with the conductive paste or the like, there is no need to consider the degree of electro-copper plating on the through-hole and the thickness of the electro-copper plating can be reduced to 15 to 20 μm. 4) Since the conductive paste or the like is filled in the through-holes, components can be mounted on the through-holes and conductors can be arranged on the through-holes, and there is no restriction on wiring routing.
Design becomes easy. In addition, high-speed signals can be handled by shortening the wiring length.

By using the double-sided smooth printed wiring board of the present invention, a metal-based smooth printed wiring board can be easily manufactured. FIG. 15 shows the manufacturing method.
FIG. 15 is a manufacturing process diagram of a metal-based two-layer smooth printed wiring board. Noble metal plating is applied to the printed wiring board 11 which has been completed up to the pattern formation in FIG. 9 or FIG. 11, a metal plate as a base, a prepreg, a smoothing jig are set up, and a smooth press is performed by performing a smooth press. You can get a board.

The double-sided smooth printed wiring board according to the present invention
Because of its excellent surface smoothness, it can be used for the following applications. 1) Printed wiring boards for sliding such as slides and rotary switches that require smooth surfaces on both sides; 2) Printed wiring boards for liquid crystal display and IC cards that require high density; 3) Build-up multilayer printed wiring boards 4) Printed wiring boards for mobile phones and portable electronic devices that require high density, 5) MCM (multi-chip module) and BGA (pole Printed wiring boards for modules such as grit arrays), 6) printed wiring boards on which IC bare chips are mounted, and 7) printed wiring boards for miniaturization, multifunctionality, and low cost of electronic equipment.

[0063]

【Example】

Example 1 As prepreg 1, glass fiber prepreg EW-3105 manufactured by Risho Kogyo Co., Ltd. is prepared. The prepreg has a thickness of 0.21 mm, a resin content of 40% by weight, and a gel time of 80 to 120 seconds at 150 ° C. As a copper foil 2 on the upper surface of this glass fiber prepreg, JAPAN ENERGY
Fig. 2 by overlaying 35 µm copper foil of JTC type
Set up according to the method of setting up the lamination bonding press shown in (1). For the cushion plate 3c, KN-42P2 for a multilayer board manufactured by Yamauchi Co., Ltd. is used, and for the stainless steel plate 3b, TPP16 manufactured by Takasago Iron Works Co., Ltd. having a thickness of 1.0 mm is used. Also, DUOFOIL manufactured by Osada Corporation having a thickness of 0.38 mm is used for the release aluminum plate 3a. As shown in FIG. 3, six units are stacked and inserted into a hot plate of a hot press as a single laminated body, and the hot press is operated based on the program shown in Table 2 to perform lamination bonding under heat and pressure. .

Subsequently, heat treatment is performed. A hot-air circulation type thermostat is used for the heat treatment. In this step, the applied heat energy is different due to the difference in the stacking position in the previous step, so the main purpose of this step is to adjust the degree of curing to make the integrated amount of heating of the heat energy uniform. . Table 2 shows the heat treatment conditions. Subsequently, the formation of the conductor pattern is performed by a method using a dry film. First, a dry film is stuck on a copper foil of a heat-treated copper-clad board with a laminator, and a film having a predetermined pattern formed thereon is exposed to ultraviolet light.
Next, the dry film film where the conductor pattern is unnecessary is removed by a dry film developing machine. Next, an unnecessary portion of the conductor pattern is removed by etching with an etching machine. Subsequently, precious metal plating to provide sliding resistance to the conductor pattern, for example, plating thickness of 5 to 15 μm
Is subjected to electric nickel plating. The noble metal plating is not limited to electric nickel, but may be another type of noble metal electroplating or electroless plating.

Subsequently, hot pressing for smoothing is performed. First, the setup shown in FIG. 5 is performed. A printed wiring board 5 having the above-described electric nickel plating and capable of being smoothed is prepared. Glass fiber prepreg EW-3105 manufactured by Risho Kogyo Co., Ltd. used as a prepreg 1 on a laminated adhesive press on the upper surface of a glass epoxy insulating plate ES-3350 manufactured by Risho Kogyo Co., Ltd. as a thermosetting resin plate 3d.
Is set. A pattern forming completed material 5 capable of smoothing is set on the upper surface. Smooth jig cushion plate 3
For c and the stainless steel plate 3b, those having the same specifications as those of the above-mentioned laminated adhesive press working are used. Even in hot press for smoothing,
One or a plurality of sheets are stacked in the same manner as in the laminating process, and inserted as a single laminated body between hot plates of a hot press. The hot press is operated based on the program shown in Table 2 and smoothed under heat and pressure. Carry out processing. Subsequently, the necessary portions are manually machined with a drilling machine or automatically drilled with an NC drilling machine. Next, the sheet is punched into a predetermined shape by a punching press or processed into a predetermined shape by an NC outer shaper to complete a smooth printed wiring board.

Table 2 shows the evaluation results of the obtained smooth printed wiring board together with the pressing conditions and the heat treatment conditions. Also,
FIG. 8 shows the result of measuring the smoothness. In Table 2, the temperature and time in the laminated adhesive press and the smoothing press are as follows:
Indicates the keep temperature and time actually applied to the unit. In addition, among the evaluation results, the etching resistance and plating resistance are visually determined by the surface roughness of the adhesive and the presence or absence of peeling of the conductor, the resin fogging is visually determined by the degree of covering of the conductor with the resin, and the resin surroundings are visually determined. The smoothness was measured using a surface roughness measuring device (trade name: SURFEST SV-524, manufactured by Mitutoyo Corporation), and the undulation curve WC was measured.
It was determined from the curve.

Example 2 As the thermosetting resin sheet 6, a semi-cured sheet B-EL10 of an epoxy thermosetting resin manufactured by Shinko Chemical Industry Co., Ltd.
Prepare This sheet has a thickness of 0.04mm and curing conditions
It is a semi-cured sheet at 150 ° C for 1 hour. The glass fiber prepreg EW-13105 manufactured by Risho Kogyo Co., Ltd. used in Example 1 is also prepared as prepreg 2. A glass epoxy insulating plate ES-3350 manufactured by Risho Kogyo Co., Ltd. is prepared as the thermosetting resin 3d, a prepreg is superimposed on the upper surface thereof, a thermosetting resin sheet 6 is superimposed on the upper surface thereof, and a copper foil 2 is formed on the upper surface thereof. As JAPAN ENE
A 35 μm copper foil of JTC type made by RGY is overlaid and set up by the setup method of the lamination adhesive press shown in FIG. KN-42P2 for multilayer board manufactured by Yamauchi Co., Ltd. is used for the cushion plate 3c, and TPP1 manufactured by Takasago Iron Works Co., Ltd. having a thickness of 1.0 mm is used for the stainless steel plate 3b.
6 is used. Six units are stacked and inserted into a hot plate between hot plates of a hot press, and the hot press is operated based on the program shown in Table 2 to perform lamination bonding under heat and pressure.

Subsequently, heat treatment is performed. A hot-air circulation type thermostat is used for the heat treatment. In this step, the applied heat energy is different due to the difference in the stacking position in the previous step, so the main purpose of this step is to adjust the degree of curing to make the integrated amount of heating of the heat energy uniform. . Table 2 shows the heat treatment conditions. Subsequently, the forming process of the conductor pattern and the electro-precious metal plating were performed in Example 1.
Perform under the same conditions.

Subsequently, hot pressing for smoothing is performed. A printed wiring board which has been subjected to the above-described electro-nickel plating and which can be smoothed is prepared. The cushion plate and the stainless plate of the smoothing jig have the same specifications as the above-mentioned laminated adhesive press working. Even in hot press for smoothing,
One or a plurality of sheets are stacked in the same manner as in the laminating process, and inserted as a single laminated body between hot plates of a hot press. The hot press is operated based on the program shown in Table 2 and smoothed under heat and pressure. Carry out processing. Subsequently, the necessary portions are manually machined with a drilling machine or automatically drilled with an NC drilling machine. Next, the sheet is punched into a predetermined shape by a punching press or processed into a predetermined shape by an NC outer shaper to complete a smooth printed wiring board. Table 2 shows the evaluation results of the obtained smooth printed wiring boards together with the pressing conditions and the heat treatment conditions.

Comparative Examples 1 to 3 One unit is set up using the same material as in Example 1 and using the same setup method as in Example 1. Table 2
The hot press is operated based on the program shown in (1), and the lamination bonding is performed under heating and pressing. Next, the conductor pattern was formed and processed under the same method conditions as in Example 1 without heat treatment.
Further, hot pressing for smoothing is performed under the conditions shown in Table 2. Table 2 shows the evaluation results of the obtained smooth printed wiring boards together with the pressing conditions and the heat treatment conditions.

Comparative Examples 4 to 6 Six units are set up using the same materials as in Example 1 and using the same setup method as in Example 1. Next, heat treatment is performed under the conditions shown in Table 2 to form a conductor pattern under the same method conditions as in Example 1, and hot press processing for smoothing is performed under the conditions shown in Table 2. Table 2 shows the evaluation results of the obtained smooth printed wiring boards together with the pressing conditions and the heat treatment conditions.

[0072]

[Table 2]

As shown in Table 2, Examples 1 and 2 were excellent in etching resistance and plating resistance, were excellent in resin fogging, did not surround the resin, and had a smoothness of 5 μm or less. On the other hand, in the comparative example, the heat treatment was not performed, the flow of the resin was unstable due to the difference in the conditions, the flow of the resin was insufficient, or the resin fogging occurred, and the ideal smoothness was obtained. Production of printed wiring boards was not possible.

Example 3 Glass fiber prepreg EW-310 manufactured by Risho Kogyo Co., Ltd.
Prepare 5 The prepreg has a thickness of 0.21 mm, a resin content of 40%, and a gel time of 80 to 120 seconds at 150 ° C. The top surface of this glass fiber prepreg is JAPAN
How to set up a laminating adhesive press by stacking 18 µm copper foil of JTC type manufactured by ENERGY (Figure 2)
Set up as shown. KN-42P2 for multilayer board manufactured by Yamauchi Co., Ltd. is used for the cushion plate 3c.
A 1.0 mm thick TPP16 manufactured by Takasago Iron Works Co., Ltd. is used for the stainless steel plate 3b. The release aluminum plate 3a has a 0.38 mm thick DU manufactured by OSADA CORPORATION.
Use OFOIL. As shown in FIG. 3, six units are stacked to form one laminated body, inserted between hot plates of a heating press, and subjected to a predetermined program (temperature: 115 ° C., time: 60 ° C.).
Min, pressure: 10 kgf / cm ² ) to operate the hot press, and perform the first-stage lamination bonding under heat and pressure.

Subsequently, two laminates of the copper foil and the prepreg after the first stage of lamination and bonding, and the prepreg EW
-3105, one unit is arranged as shown in FIG. 12, and the six units are stacked as shown in FIG. 16 to form one laminated body and inserted between hot plates of a heating press. Program (temperature: 90 ° C, time: 60 minutes,
The heat press is operated based on the pressure: 10 kgf / cm ² ), and the second-stage lamination is performed under heating and pressing. The same jigs and tools as those used in the first-stage lamination adhesive press were used.

Subsequently, heat treatment is performed. A hot-air circulation type drying furnace is used for the heat treatment. In this step, the applied heat energy is different due to the difference in the stacking position in the previous step, so the main purpose of this step is to adjust the degree of curing to make the integrated amount of heating of the heat energy uniform. . The heat treatment was performed under the same conditions as in Example 2.

Subsequently, drilling is performed. Since the adhesive of the prepreg is not completely cured, the cutting condition of the drill is 0.5 mm.
Drill rotation speed 30,000 to φ through hole hole diameter
Processing was performed with the feed rate set to 40,000 rpm and the feed rate set to 2-3 m / min. In addition, in FR-4 of the conventional double-sided printed wiring board, it is 0.
Drill rotation speed is 65,00 for through hole diameter of 5mm φ.
0 rpm, feed rate is set to 2m / min.

Subsequently, the through-hole hole wall was catalyzed with palladium, and then subjected to electroless copper plating.
Electroplated copper was applied over the entire surface to a thickness of 25 μm. After catalysis with palladium, instead of the method of performing electroless copper plating, it is also possible to conduct electricity by a direct plating method and perform electrolytic copper plating.

Subsequently, SA-1000 (one-pack type epoxy resin compound) manufactured by Asahi Chemical Laboratory Co., Ltd. was filled into the through-holes plated with copper by screen printing. After that, dry to the touch under the condition (90 ° C / 10min) where hardening of the prepreg does not progress very much.

Subsequently, a conductor pattern is formed. This processing method includes a method using dry film, a method using pattern printing, and the like. In this embodiment, a method using dry film was used. First, a dry film is laminated with a laminator to the surface of a laminated board filled with an epoxy resin compound in a through-hole by a screen printing method, and a film having a predetermined pattern formed thereon is exposed to ultraviolet light. Next, the dry film film where the conductor pattern is unnecessary is removed by a dry film developing machine. Next, unnecessary portions of the conductor pattern are removed by etching using an etching machine. Further, the dry film film on the conductor pattern is removed with a 2 to 3% aqueous sodium hydroxide solution at 50 ° C.

Subsequently, noble metal plating, for example, electric nickel plating is performed to a thickness of 5 to 15 μm in order to impart sliding resistance to the conductor pattern. The noble metal plating is not limited to the nickel electroplating, but may be another type of noble metal plating or electroless plating.

Subsequently, hot pressing for smoothing is performed. A pattern formation completed material that can be smoothed is set. The same cushion plate and stainless steel plate as the jig and tool used in the laminated adhesive press working are used. In the smoothing hot press, one or more sheets are stacked as in the case of laminating and bonding, and inserted as a block between the hot plates of the hot press. The specified program (temperature: 180 ° C, time:
The heat press is operated based on the pressure of 50 kgf / cm ² ) for 60 minutes, and smoothing is performed under heat and pressure. By operating the hot press under these program conditions, the flow of the resin is stabilized, and the surface smoothness is reduced without resin fogging.
It is possible to manufacture an ideal smooth printed wiring board of 5 μm or less.

Subsequently, the non-through hole is machined manually with a drilling machine or automatically drilled with an NC drilling machine. Next, it is punched into a predetermined shape by a punching press, or processed into a predetermined shape by an NC outer shaper to complete a double-sided smooth printed wiring board.

Example 4 The glass fiber prepreg EW-3105 manufactured by Risho Kogyo Co., Ltd. used in Example 3 was used for the prepreg 1a, and the unipreg sheet manufactured by Meiden Chemical Co., Ltd. was used for the prepreg 1b. The purpose of using these two different types of prepregs is that the curing of the three centrally located prepregs 1b is delayed more than the two outer prepregs 1a in the same manner as in Example 3, and the curing is advanced by smooth pressing. This is because the adhesive of the prepreg 1b at the center, which is not shown, pushes up the adhesive of the prepregs 1a on both outer sides to enable smoothing.

The prepreg 1b has a thickness of 0.17 to 0.1
8 mm, resin content 40-47%, gel time 150 ° C
130-180 seconds. The same materials and jigs and tools as in Example 3 are used for the copper foil, cushion plate, and stainless plate of the laminated material. One unit is set up as shown in FIG. 10 (a), and these six units are stacked to form a laminate, inserted between hot plates of a heating press, and subjected to a predetermined program (temperature: 115 ° C., time: 60 minutes). , pressure: 10 kgf / cm ²⁾
The hot press is operated based on the above, and the lamination bonding is performed under heat and pressure.

Subsequently, the heat treatment is performed. The following steps are the same as in the third embodiment. This embodiment is different from the third embodiment in that
A smooth copper-clad laminate can be manufactured by a single-stage lamination press, and the manufacturing process can be simplified.

Example 5 A double-sided smooth printed wiring board is manufactured by the method of Example 3.
However, after NC drilling, hole filling was performed using a conductive paste by the Q route shown in FIG. The conductive paste is filled by screen printing using MDP900 conductive paste manufactured by Mitsui Toatsu Chemicals, Inc. After that, dry to the touch under the condition (90 ° C / 10min) where hardening of the prepreg does not progress very much. Thereafter, a conductor pattern is formed and smooth pressing is performed in the same manner as in Example 3 to obtain a double-sided smooth printed wiring board. Using this double-sided smooth printed wiring board, a double-sided six-layer printed wiring board is manufactured.

First, two double-sided smooth printed wiring boards are prepared, a prepreg is placed between and on both surfaces of the two double-sided smooth printed wiring boards, and a copper foil is placed on the surface (FIG. 14 (a)). As the copper foil, a 18 μm copper foil of JTC type manufactured by JAPAN ENERGY is used. Six units are stacked and inserted as a single laminated body between the hot plates of a heating press, and a predetermined program (temperature: 115 ° C, time: 6
A hot press is operated based on 0 minutes and a pressure of 10 kgf / cm ² ), and the laminate is bonded under heat and pressure. The same jigs and tools as those used in Example 3 were used.

The subsequent heat treatment, punching, and smooth pressing are performed in the same manner as in Example 3 to obtain a six-layer smooth double-sided printed wiring board. According to the method of this embodiment, a multilayer printed wiring board having both surfaces smoothed can be easily obtained. In addition, a commercially available double-sided printed wiring board as well as a double-sided smooth printed wiring board can be used to obtain a multilayer printed wiring board having both sides smooth.

[0090]

Since the smooth printed wiring board of the present invention has a smoothness of a circuit forming surface of 5 μm or less, it has stable and highly reliable characteristics as a printed wiring board of a device having a movable portion and a contact switching mechanism. Obtainable. As a result, a device having a highly reliable movable part can be realized.

In the method for producing a smooth printed wiring board of the present invention, a heat treatment step is provided between the lamination adhesive pressing step and the smooth pressing step, so that a smooth printed wiring board excellent in circuit pattern formability and smoothness is obtained. Can be In addition, since the heat treatment step is performed under the heat treatment conditions in which the minimum adhesive strength in circuit formation is obtained and the smoothness of the circuit formation surface is 5 μm or less, preferably 2 μm or less, a smooth printed wiring board having the above-described characteristics is further improved. can get.

Further, when a plurality of smooth printed wiring boards are manufactured at the same time, heat treatment is performed under the heat treatment conditions that make the integrated thermal energy of each of the smooth printed wiring boards substantially equal, so that a large amount of smooth printed wiring boards having excellent smoothness can be manufactured at once. Becomes Further, by changing the setup method in the laminating and pressing step, a general etching apparatus for manufacturing a printed wiring board can be used. As a result, the production yield is improved, and a smooth printed wiring board of stable quality can be provided at low cost.

The method for producing a smooth printed wiring board of the present invention includes a step of pressing copper foils arranged on both sides of a plurality of laminated prepregs having different degrees of curing.
Also, the plurality of prepregs are three prepregs,
Since the prepreg arranged on the copper foil side has a higher degree of curing than the prepreg arranged inside, the smoothness of the circuit forming surface of the double-sided printed wiring board is 5 μm or less, and both sides are smoothed to achieve high density. A printed wiring board is obtained.

The method for producing a smooth printed wiring board according to the present invention can provide a multilayer printed wiring board having a double-sided printed wiring board as an inner layer, in which the smoothness of the circuit formation surface is 5 μm or less, preferably 2 μm or less, Thus, a double-sided smooth printed wiring board which can be manufactured can be obtained.

In the method of manufacturing a smooth printed wiring board of the present invention, the above-mentioned double-sided smooth printed wiring board can be used also in the method of manufacturing a smooth printed wiring board based on a metal plate. Even with this, a printed wiring board excellent in smoothness can be obtained.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a manufacturing process of a printed wiring board of the present invention.

FIG. 2 is a diagram showing an example of a setup in a lamination bonding press step.

FIG. 3 is an example of a case where six units are stacked in a lamination adhesive pressing process.

FIG. 4 is a diagram showing the results of measuring the relationship between temperature and time in each unit.

FIG. 5 is a diagram showing an example of a setup in a smooth press step.

FIG. 6 is a flowchart showing another manufacturing process of the printed wiring board of the present invention.

FIG. 7 is a diagram showing another example of the setup in the lamination bonding press step.

FIG. 8 is a diagram showing a result of measuring smoothness.

FIG. 9 is a flowchart showing a manufacturing process of a double-sided smooth printed wiring board.

FIG. 10 is a cross-sectional view of a double-sided smooth printed wiring board in a manufacturing process along a Q route.

FIG. 11 is a flowchart showing another manufacturing process of the double-sided smooth printed wiring board.

FIG. 12 is a layout diagram of a prepreg and a copper foil in a lamination bonding press step.

FIG. 13 is a layout diagram of a double-sided printed wiring board and the like, a prepreg, and a copper foil.

FIG. 14 is a cross-sectional view of a double-sided smooth six-layer printed wiring board.

FIG. 15 is a manufacturing process diagram of a metal-based two-layer smooth printed wiring board.

FIG. 16 is an example of a case where six units of double-sided printed wiring are stacked.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pre-preg 2 Copper foil 3 Laminating jig 3a Release aluminum plate 3b Stainless steel plate 3c Cushion plate 3d Thermosetting resin plate 4 Hot plate of hot press 5 Printed wiring board with circuit pattern formed 6 Thermosetting resin sheet 7 Filling material 8 Copper plating layer 10 Inner layer board 11 Printed wiring board

Claims (9)

[Claims] 1. A smooth printed wiring board having a smooth circuit formation surface on a printed wiring board, wherein a copper foil and a prepreg are laminated and pressed to form a circuit and then heat-treated before the smooth pressing. A smooth printed wiring board characterized in that the smoothness of the formation surface is 5 μm or less. 2. A method for manufacturing a smooth printed wiring board, comprising: a lamination adhesive pressing step of laminating and pressing at least one set of copper foil and prepreg; and a smooth pressing step after circuit formation. A method for manufacturing a smooth printed wiring board, comprising a heat treatment step of heating the smooth printed wiring board between the smooth press step. 3. The smooth printing according to claim 2, wherein the heat treatment step is performed under heat treatment conditions such that the minimum adhesive force in the circuit formation is obtained and the smoothness of the circuit formation surface is 5 μm or less. Manufacturing method of wiring board. 4. When simultaneously manufacturing a plurality of smooth printed wiring boards, the heat treatment step is performed under heat treatment conditions that make the thermal energy integrated amounts of the plurality of smooth printed wiring boards substantially equal before the smooth pressing step. The method for manufacturing a smooth printed wiring board according to claim 2 or 3, wherein: 5. The method according to claim 2, wherein the laminating and pressing step includes a step of pressing copper foils disposed on both surfaces of a plurality of prepregs having different degrees of hardening. A method for producing a smooth printed wiring board according to any one of the preceding claims. 6. The prepreg according to claim 5, wherein the plurality of prepregs are at least three prepregs, and the prepreg disposed on the copper foil side has a higher degree of curing than the prepreg disposed inside. Of manufacturing a smooth printed wiring board. 7. The laminating and bonding pressing step includes a step of laminating at least one double-sided printed wiring board via the prepreg, and laminating copper foils disposed on both surfaces via the prepreg. 3. The method for manufacturing a smooth printed wiring board according to claim 2, wherein 8. A method for manufacturing a smooth printed wiring board having a smooth pressing step in which the double-sided printed wiring board is laminated and pressed with a metal plate via a prepreg, wherein the double-sided printed wiring board is smooth-printed according to claim 6. A method for manufacturing a smooth printed wiring board, which is a double-sided smooth printed wiring board obtained by the method for manufacturing a wiring board. 9. The smooth printing according to claim 2, wherein the heat treatment step is performed under a heat treatment condition such that a minimum adhesive force in the circuit formation is obtained and the smoothness of the circuit formation surface is 2 μm or less. Manufacturing method of wiring board.