JPH06350250A - Production of printed wiring board - Google Patents

Abstract

PURPOSE:To provide a method for producing a highly reliable printed wiring board with high yield through a simple process while allowing high density wiring and mounting. CONSTITUTION:The method for producing a printed wiring board comprises a step for arranging a columnar conductive paste at a predetermined position on the main surface of a first base body, a step for positioning the second main surface of the base body at the leading end face of a protruding conductive paste, and a step for separating the opposing faces of the first and second base bodies to elongate the protruding conductive paste substantially in the center and cutting the paste to form a pointed conductive bump. The production method further comprises a step for laminating the conductive bump on a forming face while bringing the main surface of a synthetic resin sheet into contact therewith, and a step for heating the laminate to plastisize the resin component of the synthetic resin sheet and then pressing the laminate to be pierced with the conductive bump in the direction of thickness thus forming a through type conductor wiring part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, and more particularly, it has a structure for connecting wiring layers in a through-type conductor wiring portion and has high reliability for high-density wiring and mounting. The present invention relates to a method capable of manufacturing a high printed wiring board with a good yield while reducing the number of steps.

[0002]

2. Description of the Related Art For example, in a double-sided printed wiring board or a multi-layered printed wiring board, electrical connection between wiring layers such as double-sided conductive patterns is made as follows. That is, in the case of a double-sided printed wiring board, perforation processing (perforation processing) is performed at a predetermined position on the double-sided copper foil-clad substrate, and chemical plating treatment is applied to the entire surface including the inner wall surface of the perforated hole. The thickness of the metal layer on the inner wall surface of the hole is increased by electroplating to improve reliability and to electrically connect the wiring layers. Also, in the case of a multilayer printed wiring board, after patterning the copper foils stretched on both sides of the board, copper foils are laminated and arranged on the patterned surfaces with an insulating sheet (for example, a prepreg layer) interposed between them, and heated and pressed. After the integration, the multi-layer printed wiring board is obtained by electrical connection between wiring layers by punching and plating, and patterning on the surface copper foil, as in the case of the double-sided printed wiring board described above. . A multilayer printed wiring board having more wiring layers can be manufactured by a method of increasing the number of double-sided printed wiring boards to be inserted in the middle.

In the method of manufacturing a printed wiring board described above, as a method of electrically connecting wiring layers without using a plating method, a hole is formed at a predetermined position of a double-sided copper foil-clad substrate, and a conductive paste is placed in the hole. There is also known a method of pouring / filling by a printing method or the like, and hardening the conductive paste poured / filled in the holes to electrically connect wiring layers.

[0004]

As described above, in a method of manufacturing a printed wiring board that utilizes a plating method for electrical connection between wiring layers, holes for electrical connection between wiring layers are formed in a substrate. It has the drawbacks of requiring opening (perforation) processing, a plating process including the inner wall surface of the bored hole, a redundant manufacturing process of the printed wiring board, and complicated process control. On the other hand, in the case of embedding a conductive paste in the holes for electrical connection between the wiring layers by printing,
As in the case of the plating method, a drilling step is required.
In addition, it is difficult to evenly (uniformly) pour and embed the conductive paste into the bored holes, and there is a problem in reliability of electrical connection.

In any case, the necessity of the perforating step is reflected in the cost and yield of the printed wiring board, and it is not possible to meet the demand for cost reduction, and further high density wiring is required. Along with this, if the diameter of the drilled hole is relatively small, there is a drawback that it is difficult to achieve highly reliable electrical connection by plating or filling with a conductive paste. Further, in the case of the electrical connection configuration between the wiring layers, since conductor holes for wiring layer connection are installed on the front and back surfaces of the printed wiring board, the wiring is formed and arranged in the area of the conductor holes. This is not possible, and in addition, since electronic parts cannot be mounted, there is a problem that improvement in wiring density is restricted and improvement in mounting density of electronic parts is also hindered. That is,
The printed wiring board obtained by the conventional manufacturing method cannot be said to sufficiently meet the demands for compact circuit devices by high-density wiring and high-density mounting, and eventually for miniaturization of electronic devices, and the above cost aspect is not satisfied. Including the above, a practically more effective method for producing a printed wiring board is desired.

The present invention has been made in consideration of the above circumstances, and provides a method capable of producing a printed wiring board having a high yield, which enables high-density wiring and mounting by a simple process and has high reliability. With the goal.

[0007]

A method of manufacturing a printed wiring board according to the present invention comprises a step of arranging a conductive paste in a protrusion shape at a predetermined position on a first main surface of a substrate, and the protrusion-shaped conductor arranged as described above. Of the main surface of the second base body to the tip surface of the conductive paste, and the facing surfaces of the first base body and the second base body are separated from each other, and the conductive paste in the shape of a protrusion is stretched almost at the center. Cutting and forming a conductive bump having a sharp tip; a step of stacking the conductive bumps on the surface on which the synthetic resin sheet main surface is in contact; and heating the stack. The laminated body is pressed at a temperature at which the resin content of the synthetic resin sheet becomes plastic, and the conductive bumps are inserted in the thickness direction of the synthetic resin sheet to form a through-type conductor wiring portion. And a process.

In the present invention, examples of the first substrate on which the conductive bumps are formed include synthetic resin sheets having good releasability or conductive sheets (foil). The first substrate is more preferably a single sheet from the viewpoint of workability, but it may be patterned in advance, and its shape is not particularly limited. In the present invention, the protruding conductive paste is cut,
As the second substrate having a form in which a part of it is transferred,
For example, synthetic resin sheets or a conductive sheet (foil) having good peelability can be used.

In the present invention, the conductive paste used for forming the conductive bumps is, for example, conductive powder such as silver, gold, copper, solder powder, alloy powder or composite (mixed) metal powder of these, and, for example, polycarbonate. resin,
Examples thereof include those prepared by mixing with a binder component such as polysulfone resin, polyester resin, phenoxy resin, phenol resin and polyimide resin. The conductive paste is required to have required conductivity and have a certain degree of viscosity in an undried state, while exhibiting a certain degree of hardness or the like when dried, and the conductive paste protrusion ( The columnar bodies can be formed by, for example, a printing method using a relatively thick metal mask to form protrusions (columnar bodies) with a high aspect ratio,
The heights, diameters, and distributions of the protrusions or columnar bodies are appropriately set according to the configuration of the through-hole type conductor wiring portion to be formed. Specifically, it is determined in consideration of the layout structure of the through-type conductor wiring part to be finally configured. For example, when the synthetic resin sheet is a B-stage epoxy resin layer containing glass cloth, press-fitting is applied from both sides. 80 to 120% of the thickness of the B-stage epoxy resin layer in the case of the press-fitting mode, and 180-120% of the thickness of the B-stage epoxy resin layer in the case of press fitting from one side
A height of about 220% is preferable. The protrusions (pillars) are arranged, for example, on a stainless steel plate having a thickness of about 5 mm at a predetermined position by arranging a mask having a hole of 0.3 mm on the entire surface of the housing, and the conductive material housed in the housing. It is also possible to use a so-called stamp method in which the conductive paste is pressed and the conductive paste is pushed out from the holes of the mask. In addition, when the protruding conductive paste arranged as described above is cut and a part of the conductive paste is transferred to the second substrate to form a projection (columnar body) having a sharp tip, cutting and drying are performed to a certain degree. It is possible to impart a certain degree of hardness, or if a certain degree of hardness is imparted by drying prior to cutting, it is easy to form a material having a high aspect ratio. Further, the arrangement is, for example, a wiring board in which the through-hole conductor wiring portions are arranged in a matrix at a constant pitch, and the through-hole conductor wiring portions are arranged in a matrix, and the through-hole conductor wiring portions are arbitrarily selected and used. May be.

In the present invention, examples of the synthetic resin sheet having the conductive bumps inserted therethrough to form a through-type conductor wiring portion include a thermoplastic resin film (sheet) having a thickness of 25 to About 300 μm is preferable. Here, examples of the thermoplastic resin sheet include sheets of polycarbonate resin, polysulfone resin, thermoplastic polyimide resin, tetrafluoropolyethylene resin, hexafluoropolypropylene resin, polyetheretherketone resin, and the like. Further, as the thermosetting resin sheet to be kept in the pre-curing state, epoxy resin, bismaleimide triazine resin, polyimide resin, phenol resin,
Examples thereof include polyester resins, melamine resins, and raw rubber sheets such as butadiene rubber, butyl rubber, natural rubber, neoprene rubber, and silicone rubber. These synthetic resins may be used alone or may contain an insulating inorganic or organic filler, and are a sheet formed by combining with a reinforcing material such as glass cloth or mat, organic synthetic fiber cloth or mat, or paper. It may be.

Further, according to the present invention, the second base main surface is opposed to the first main base surface on which the projection (columnar body) of the conductive paste is formed, and the projections or columnar bodies are lightly pressure-bonded. When pressure is applied when cutting at approximately the center, or after the conductive bumps are formed, when the laminated body made by stacking the synthetic resin sheet main surfaces in contact with each other is heated and pressed, the size of the contact plates on both sides It is desirable to use a metal plate or a heat-resistant resin plate with little deformation, such as a stainless plate, a brass plate, a polyimide resin plate (sheet), or a polytetrafluoroethylene resin plate (sheet).

[0012]

According to the method of manufacturing a printed wiring board according to the present invention,
The conductor wiring portion between the layers for electrically connecting the wiring layers is heated and pressed in a so-called laminated integration process so that the synthetic resin sheet forming the interlayer insulating layer is plasticized and the tip of the support base surface is By press-fitting the sharp conductive bumps, reliable electrical connection between wiring layers is achieved.
In other words, while simplifying the process such as omitting the step of forming holes for interlayer connection, highly precise and reliable electrical connection is formed at any position (location) between fine wiring pattern layers. Therefore, it becomes possible to manufacture a printed wiring board having a high wiring density at low cost, and it is not necessary to form a connection hole for electrical connection between the wiring pattern layers. And a printed wiring board capable of high-density mounting can be obtained.

[0013]

Embodiments of the present invention will be described below with reference to FIGS.

Example 1 FIGS. 1 to 7 schematically show an embodiment of this example. First, a 50 μm thick polyimide resin film (trade name, Kapton film, Toray KK) is used as the first base sheet 1, and a polysulfone resin having a viscosity of 700 dPa · s (25 ° C.) and a thixo ratio of 7.5 (1 rpm: 10 rpm). As a conductive paste, a silver paste (92% of the silver composition ratio when dried) was used as a binder, and a metal mask having a 0.4 mm diameter hole was prepared at a predetermined position of a stainless steel plate having a plate thickness of 100 μm. Then, the metal mask was positioned and arranged on the surface of the polyimide resin film 1, and the conductive paste was screen-printed to apply and form the projections (columnar bodies) 2 of the conductive paste. After that, the polyimide resin film 1 on which the columnar body 2 of the conductive paste is applied and formed is adhered to the surface of the stainless steel plate 3 having a thickness of 10 mm by thermocompression bonding to maintain the flatness, while the surface of the stainless steel plate 3'having a thickness of 10 mm is separately attached. Second
A polyimide resin film 1'as a substrate was attached by thermocompression to maintain its flatness. Next, the polyimide resin films 1 and 1 ′ attached to the stainless steel plates 3 and 3 ′ are opposed and arranged as shown in a sectional view in FIG. The polyimide resin film 1'that forms the substrate of Fig. 2 was lightly pressure-bonded to obtain a state as shown in a sectional view in Fig. 2.

As described above, after the conductive paste columnar body 2 is pressure-bondedly held between the opposing polyimide resin films 1 and 1'side, both polyimide resin films 1 and 1 '
When the opposing surfaces of 1'are gradually separated, the conductive paste columnar body 2 is in a dry state, so that the conductive paste columnar bodies 2 are expanded as shown in a sectional view in FIG. 3, corresponding to the separation between the opposed surfaces. When the heat treatment is appropriately applied in the process of extending the conductive paste columnar body 2, the conductive paste columnar body 2 is dried and hardened (solidified), while it is pulled and cut at substantially the center portion to form a cross-section in FIG. As shown in FIG. 3, the conductive bumps 4 having sharp tips were formed at the main surface positions (locations) corresponding to each other.

Next, a synthetic resin sheet 5 containing glass cloth, that is, a polyphenylene sulfide resin impregnated / adhered thickness of 75 μm is provided between the surfaces of the polyimide resin films 1 and 1'on which the conductive bumps 4 having sharp tips are formed. A synthetic resin sheet 5 having a glass cloth weave density of 60 × 46/25 mm and a thickness of 60 μm is arranged as shown in a sectional view in FIG.
It is placed between hot plates of a hot press maintained at about 300 ° C (not shown), and when the synthetic resin sheet 5 is in a thermoplasticized state, it is pressurized with a resin pressure of 500 MPa, then cooled and taken out, When the front and back sheets 1 and 1'are peeled off, as shown in FIG.
As shown in cross section, the opposing conductive bumps 4 are press-fitted into the synthetic resin sheet 5, and the opposing conductive bumps 4 are connected to each other and penetrate in the thickness direction of the synthetic resin sheet 5. A printed wiring board including the conductor wiring portion 6 was obtained.

With respect to the through-hole type conductor wiring portions 6 formed as described above, a continuity test was conducted on the respective conductor wiring portions 6 from the front and back sides with a tester. As a result, the total resistance was 0.5 Ω or less. Also,
A conductive paste wiring pattern was formed by printing on both surfaces of the printed wiring board, and the penetrating conductor wiring portion 6 was utilized to exert a sufficient function as a double-sided conductive printed wiring board.

In the above embodiment, the required metal mask is positioned and arranged on the surface of the polyimide resin film, the conductive paste is screen-printed, and the projections (columnar bodies) 2 of the conductive paste are arranged at regular intervals. The conductive bumps 4 facing each other are press-fitted into the synthetic resin sheet 5 in the same manner except that the conductive bumps 4 are applied and formed in a similar manner, and the conductive bumps 4 facing each other are connected to each other. To obtain a printed wiring board in which the conductor wiring portions 6 penetrating in the thickness direction of the synthetic resin sheet 5 as shown in FIG. And
A conductive paste wiring pattern is formed by printing on both sides of this printed wiring board, and a part of the through-type conductor wiring portion 6 is selectively used to exert a sufficient function as a double-sided conduction type printed wiring board. .

Embodiment 2 FIGS. 8 and 9 are sectional views schematically showing an embodiment of this embodiment. In this example, in the case of the above-mentioned Example 1, a polyimide resin film was used as the first base sheet 1, and a thickness normally used for manufacturing a printed wiring board.
An 18 μm electrolytic copper foil 1a ′ (second substrate sheet 1 ′) with a single-sided B-stage glass cloth-containing epoxy resin sheet 5 further having a viscosity of 600 dPa · s (25 ° C.) and a thixo ratio of 5.5 (1
A silver paste (silver composition ratio of 92% when dried) using an epoxy resin as a binder (rpm: 10 rpm) was prepared as a conductive paste.

Then, in the same manner as in Example 1, first, the polyimide resin film 1 having the conductive bumps 4 with sharp tips as shown in FIG. As shown in a sectional view in FIG. 8, conductive bumps 4 are laminated on the surface of the epoxy resin sheet 5 containing glass cloth so as to face the surface of the epoxy resin sheet 5, and the laminated body is 120 ° C. and the resin pressure is 500 kPa. After press working under the conditions described above, the temperature was raised to 170 ° C. to cure the resin component of the epoxy resin sheet 5. After that, when cooled and taken out and the polyimide resin film 1 was peeled off,
As shown in a sectional view in FIG. 9, the conductive bumps 4 having sharp tips penetrate the epoxy resin sheet 5, and the tips thereof are electrically connected to the electrolytic copper foil 1a ′ surface. Created a veneer. On the copper foil 1a 'side of this copper foil 1a' clad plate,
Normal etching resist ink (product name, PSR-4000
H, Taiyo Ink KK) was screen-printed to mask the conductor pattern portion, and after the etching treatment with cupric chloride as an etching solution, the resist mask was peeled off to obtain a double-sided printed wiring board. When the thus-produced double-sided printed wiring board was subjected to an electrical check that is usually carried out, no problems such as defects or reliability were found in all connections.

Example 3 This example is the same as the above Example 2, except that the first base sheet has a thickness of 35 mm instead of the polyimide resin film.
Under the same conditions as in Example 2 except that the electrolytic copper foil of μm was used, first, conductive bumps having sharp tips were respectively formed at the facing positions of the both electrolytic copper foil surfaces, and then these tips were formed. A double-sided copper with conductor wiring part in which synthetic resin sheets are stacked in layers between the facing surfaces of sharp conductive bumps and subjected to heating and pressure processing, and a through-type connection is made between both electrolytic copper foils. Created a veneer.

A normal etching resist ink (trade name, PSR-4000 H, manufacturer: Taiyo Ink KK) is screen-printed on both sides of this double-sided copper clad board, and after masking the conductor pattern portion, cupric chloride After the etching treatment with the above as an etching solution, the resist mask was peeled off to obtain a double-sided printed wiring board. Regarding the double-sided printed wiring board manufactured in this way,
When the electrical check that was normally performed was performed, no problems such as defects or reliability were found in all the connections. In addition, in order to evaluate the reliability of the connection between the double-sided conductive patterns, a hot oil test (a cycle of immersion in oil at 260 ° C for 10 seconds and immersion in oil at 20 ° C for 20 seconds 1
As a cycle), no defect was observed even after 500 times, and the connection reliability between the conductive (wiring) pattern layers was remarkably excellent as compared with the case of the conventional copper plating method.

[0023]

According to the present invention, the steps of forming conductive bumps for connecting conductor (wiring) pattern layers, the steps of arranging synthetic resin sheets in a laminated manner and hot pressing, and the steps of patterning the outer layer are included. It becomes possible to easily manufacture a double-sided printed wiring board or a multilayer printed wiring board while simplifying the process, in other words, reducing the number of manufacturing steps to a significantly smaller number of steps as compared with the conventional manufacturing method. Particularly in the production of a multilayer printed wiring board in which many steps are repeated, the number of steps is significantly reduced, which is effective in improving productivity or mass productivity. Then, since the punching step and the plating step, which are indispensable in the conventional manufacturing process of the multilayer printed wiring board and the like, are not necessary, the defects occurring in the manufacturing process are significantly suppressed, and the yield is improved. Not only that, a highly reliable printed wiring board can be obtained.

Further, since the printed wiring board to be manufactured does not have holes for interlayer connection on the surface, the wiring density can be remarkably improved, and the mounting area for electronic parts can be irrespective of the position of the holes. Since it can be set, the mounting density is significantly improved, and the distance between the mounted electronic components can be shortened.
The performance of the circuit can be improved. That is, it can be said that the present invention not only contributes to the reduction of the cost of the printed wiring board, but also contributes to the downsizing of the mounted circuit device and the high performance thereof.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an embodiment of the present invention, showing a state in which a first substrate surface provided with protrusions of a conductive paste is arranged so as to face a second substrate surface.

FIG. 2 schematically shows an embodiment example of the present invention, in which a second conductive paste projection provided on a first substrate surface is opposed to a second conductive paste projection.
FIG. 4 is a cross-sectional view showing a state in which the substrate surface is pressed against.

FIG. 3 schematically shows an embodiment of the present invention, and is a cross-sectional view showing a state in which a conductive paste protrusion that is separated from the first substrate and the second substrate and pressed against each other is stretched.

FIG. 4 is a cross-sectional view schematically showing an embodiment of the present invention, showing a state in which a first substrate and a second substrate are separated and conductive paste projections are cut to form conductive bumps.

FIG. 5 schematically shows an embodiment example of the present invention, in which the conductive bump formation surfaces of the first substrate and the second substrate are
FIG. 3 is a cross-sectional view showing a state in which a synthetic resin sheet is interposed and stacked.

FIG. 6 schematically shows an embodiment example of the present invention, in which a first substrate, a synthetic resin sheet, and a second substrate laminate are hot pressed to penetrate the synthetic resin sheet in the thickness direction. FIG. 4 is a cross-sectional view showing a state in which the first substrate and the second substrate are separated after the conductor wiring portion to be formed is press-fitted.

FIG. 7 is a perspective view showing a main part of a printed wiring board manufactured according to another embodiment of the present invention.

FIG. 8 is a schematic view showing still another embodiment of the present invention, showing a state in which the conductive bump formation surface of the first substrate is aligned and arranged on a single-sided copper foil-clad synthetic resin sheet. Fig.

FIG. 9 is a perspective view showing a main part of a single-sided copper foil-clad printed wiring board manufactured according to still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st base | substrate 1 ', 1a' ... 2nd base | substrate 2 ... Conductive paste protrusion (columnar body) 3, 3 '... Stainless plate (supporting plate) 4 ... Conductive bump 5 ... Synthetic resin type sheet 6 ... Interlayer penetration type conductor wiring part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Arai, 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside the Komukai factory, Toshiba Corporation (72) Inventor Sadao Furuwato, Komukai-Toshiba, Kawasaki-shi, Kanagawa Town No. 1 Incorporation company Toshiba Komukai factory

Claims (1)

[Claims] 1. A step of arranging a conductive paste in a protruding shape at a predetermined position on a first main surface of a base, and a step of bringing the second main surface of a substrate into contact with the end surface of the protruding conductive paste thus arranged. And separating the facing surfaces of the first and second substrates,
A step of forming a conductive bump having a sharp tip by stretching and cutting at approximately the center of the protruding conductive paste; and stacking the conductive bump-forming surface with the synthetic resin sheet main surface in contact with each other. The step of arranging, the laminated body is heated and the laminated body is pressed at a temperature at which the resin content of the synthetic resin sheet becomes a plastic state, and the conductive bump is penetrated in the thickness direction of the synthetic resin sheet. And a step of forming a penetrating conductor wiring portion, the method for manufacturing a printed wiring board.