JPH0472399B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a highly reliable multilayer wiring board in which connection between component lead wires and wiring patterns is ensured in an electrical component insertion portion.

In order to facilitate understanding of the present invention, a multilayer wiring board previously proposed by the present applicant will be described. This multilayer wiring board has an insulating base material 1 as shown in FIG.
After forming a first wiring pattern 2 made of conductive foil, for example, copper foil on one surface, a desired insulating resin layer 3 is formed except for the connecting portion 2a of the first wiring pattern 2,
Furthermore, a conductive foil such as a copper foil with an adhesive 4 applied to the back surface thereof is laminated and combined, this copper foil is selectively etched to form a second wiring pattern 5, and then a second wiring pattern 5 is formed.
The adhesive 4 in the opening provided in the connection part 5a of the first wiring pattern 5 is removed, and the electrical component insertion hole 6 is inserted so as to pass through the center of the connection part 2a of the first wiring pattern 2 facing into the opening. After that, the lead 8 of the electrical component 7 is inserted into the insertion hole 6, and the lead 8 and the connecting parts 2a and 5a are electrically connected with a conductive material 9 such as solder or the like. is made to connect to. This multilayer wiring board has advantages over conventional multilayer wiring boards, such as being able to provide high-density circuits and being manufactured at low cost.

However, in this case, at the connection portion between the wiring patterns 2 and 5 where the electrical component insertion hole 6 is formed, the connection portion 5a of the upper layer wiring pattern 5 surrounds the insertion hole 6, as shown in the enlarged drawing of FIG. It is formed into an annular shape with a closed inner peripheral surface.
For this purpose, after forming the upper layer wiring pattern 5, the adhesive 4 facing the opening of the connection portion 5a is swollen with an organic solvent (removal liquid), or is then removed by mechanical brushing ( When the upper surface of the connection part 2a of the so-called lower layer wiring pattern is activated, adhesive re-dissolution contamination occurs due to pooling of the stripping liquid, and mechanical brushing cannot be performed satisfactorily at the opening due to the presence of the peripheral wall, resulting in poor connection. There was a fear that the activation of the upper surface of the portion 2a would be insufficient, and as a result, the electrical contact with the conductive substance 9 would be insufficient and the electrical resistance would increase. For example, when filling the conductive substance 9 with a molten solder dip, an air pocket 10 is generated in the opening as shown in FIG. There was a fear that stress during heat due to gas, moisture, and bubbles remaining in the adhesive 4 of the portion 5a would adversely affect the conductive material 9.

The present invention improves the above-mentioned problems and provides a method for manufacturing a multilayer wiring board with higher reliability.

Embodiments of the method for manufacturing a multilayer wiring board according to the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows an embodiment of the present invention, which is shown in the order of steps. In this example, an insulating substrate (for example, a rigid insulating substrate such as paper phenol or paper epoxy, or a flexible insulating substrate is also possible) 21
A copper-clad laminate having a conductive foil, such as copper foil, coated on one main surface of the substrate is prepared, and the first wiring pattern 22 is formed by selectively etching the copper foil. At this time, in order to improve the adhesion between the first wiring pattern 22 and the insulating layer to be formed next, the first wiring pattern 22 is
It is possible to apply surface treatment to 2. In addition to blackening treatment, surface treatments include chemical roughening treatment to form an oxide film of CuO, Cu ₂ O, etc. on the surface, mechanical roughening treatment by sandblasting or brushing, and the like. Next, as shown in FIG. 3B, an insulating layer 23 made of, for example, an ultraviolet curable resin is placed on the base material 21 including the first wiring pattern 22 at the connecting portion of the first wiring pattern 22 (not shown in the illustrated example). 22a (circular shape) are formed by printing. The insulating layer 23 is formed by so-called reciprocating printing in which a squeegee is moved back and forth. According to this, even if the shoulder portion of the first wiring pattern 22 is in the shadow, the shadow portion is sufficiently coated due to the reciprocal coating, and an insulating layer 23 without pinholes can be formed.

Next, as shown in FIG. 3C, a conductive foil such as a copper foil 25 with a semi-cured adhesive 24 applied to the back side is inserted into a roll laminating device (for example, between a pair of hot rolls heated to 180° C.). Base material 2 using
Laminated and combined on 1. This semi-cured adhesive 2
4 is the property of a conductive foil (such as a copper foil) to be selectively etched later, which is not affected by the etching solution, but dissolves in an organic solvent, and is finally three-dimensionally cured by applying curing energy such as an electron beam or heat. It has the following.

Next, as shown in FIG. 3D, selective etching is performed on the copper foil 25 using an aqueous solution of ferrous chloride (etching solution) to form a second wiring pattern 26. At this time, the connecting portion 26a of the second wiring pattern 26 with the first wiring pattern 22 does not have a shape having a closed inner circumferential surface (so-called annular shape), but as shown in the figure, the connecting portion 26a of the first wiring pattern 22
For example, in the illustrated example, it is formed into a substantially semicircular shape so as to partially overlap with a. During this selective etching of the copper foil 25, the adhesive 24 on the back surface is not removed.

Next, as shown in FIG. 3E, a solder resist layer 27 is formed by printing except for the portions corresponding to both the connecting portions 22a and 26a. This solder resist layer 27 can be made of an ultraviolet curing resin such as epoxy acrylate resin, and has a property that it is not affected by the organic solvent used to peel off the adhesive 24. Then, this solder resist layer 27 and the second wiring pattern 26
Using the connecting portion 26a of the first wiring pattern 22, that is, the copper foil as a mask, the exposed semi-hardened adhesive 24 of the portion corresponding to the connecting portion 22a of the first wiring pattern 22 is selectively dissolved and peeled off using an organic solvent (for example, a methylene chloride solution). Then, the surface of the connecting portion 22a is exposed.

Next, the connection portion 22a of the first wiring pattern 22
The base material 21 is pressed by mechanical means such as pressing so that the central part thereof includes at least a portion 33 where the connecting portion 26a of the second wiring pattern 26 does not overlap.
An electrical component insertion hole 28 is formed so as to penetrate therethrough. Next, the semi-cured adhesive 24 is cured by electron beam or heat to obtain a multilayer wiring board 29 shown in FIG. 3F. Although the insertion hole 28 was formed in the process shown in FIG. 3F, it is also possible to form the insertion hole 28 in advance before the selective etching of the copper foil shown in FIG. 3A. This is to prevent the adhesive strength of the connecting portion 22a to the base material 21 from decreasing due to the impact when drilling with a press, and when the copper foil is coated on the entire surface of the base material 21. If press holes are made, a decrease in adhesive strength can be avoided.

Thereafter, the lead wire 31 of the electrical component 30 is inserted into the insertion hole 28 as shown in FIG. Connecting. The conductive substance 32 may be solder (solder flow, manual soldering,
Conductive materials such as reflow with solder cream, solder coater leveler), gallium alloy (which has the property of forming a paste at initial working temperature and then becoming alloyed and solidifying over time), silver paint, carbon paint, copper paint, etc. can be used. .

Multilayer wiring board 29 manufactured by such method
According to the above, in the connection portion between the lead wire and the wiring pattern in the electrical component insertion hole, the connection portion 26a of the upper layer wiring pattern 26 is not annular but semicircular such that it partially overlaps the connection portion 22a of the lower layer wiring pattern 22. Since the shape is formed, there is no pooling of the removing liquid when removing the adhesive 24 from the connecting portion 27 with the lead wire, and sufficient mechanical brushing can be performed, so that the adhesive 24 can be removed reliably. As a result, the upper surface of the lower connecting portion 22a is clearly exposed, and electrical contact with the conductive substance 32 is improved. In this case, the first and second wiring patterns 22,
Both the connecting parts 22a, 26a of 26 are laminated together using a semi-cured adhesive, so both the connecting parts 22a, 26a
The insulation layer between 6a is extremely thin (about 15 to 30 μm).
Therefore, the electrical connection can be made very easily and reliably with the conductive material 32. Conductive material 3 with molten solder dip
When attaching the number 2, air in the lower layer connection part can easily escape, the solder rises well, and good soldering can be achieved. Therefore, even when an automatic flow soldering device is used, for example, solder does not separate between the connecting portions 22a and 26a, and reliability is improved. At the same time, since the upper layer connecting portion 26a has a small area, there is less gas, moisture, and air bubbles remaining in the adhesive 24 below it, and therefore the effects of heat stress caused by these on the conductive material 32 are reduced. Become. Furthermore, when the connecting part 26a is made into an annular shape as in the first example, the inner diameter d is determined by taking air escape into account, and the width a is also required to be at least 0.3 mm.
As a result, there is a limit to how small the connecting portion 26a can be made. However, since the connection portion 26a formed as in this embodiment does not have such restrictions, a higher density wiring pattern can be formed. In addition, the solder resist layer 27 and the second wiring pattern 26
The exposed adhesive 24 of the first wiring pattern 22 corresponding to the connection part 22a is removed using the connection part 22a of the first wiring pattern 22 as a mask.
Since the connecting portion 22a is exposed, it becomes possible to process this exposed portion into a fine and arbitrary shape.

In addition to the semicircular shape shown in FIGS. 3 and 4, the shape of the upper layer connecting portion 26a may be, for example, the narrowed shape shown in FIG. 5 or the shape shown in FIG. Instead, any shape can be selected as long as it partially overlaps with the lower connecting portion 22a.

FIG. 7 shows another embodiment of the invention. In this example, as shown in FIG. 7A, a first wiring pattern 22 made of copper foil, for example, is formed on one main surface of the insulating base material 21 in the same way as on the upper surface, and this wiring pattern 22 is subjected to surface treatment. After that, as shown in Figure 7B, the first
The insulating resin layer 2 except for the connecting portion 22a of the wiring pattern 22 and a portion 21a of the base material 21 adjacent thereto.
3 is formed by printing. As shown in FIG. 7C, a semi-cured adhesive 24 is applied to the entire surface of this base material 21.
For example, copper foils 25 with markings are laminated and combined, and then,
This copper foil 25 is selectively etched to form a second wiring pattern 26. In forming the second wiring pattern 26, the connecting portion 26a is arranged so as not to overlap the connecting portion 22a of the first wiring pattern 22 in the lower layer, that is, adjacent to the connecting portion 22a, as shown in FIG. 7D. It is formed on the portion 21a of the base material 21. Therefore, both the connecting portions 22a and 26a are formed substantially flush with each other without creating a step. Next, as shown in FIG. 7E, both the connecting portions 22a and 2
The solder resist layer 27 is formed by printing except for the solder resist layer 27 and the upper layer second wiring pattern 26, and using the connecting portion 26a of the solder resist layer 27 and the upper layer second wiring pattern 26, that is, the copper foil as a mask, the semi-cured state on the connecting portion 22a is formed. The adhesive 24 is dissolved and peeled off using an organic solvent.
Next, an electrical component insertion hole 28 penetrating the base material 21 is formed in the center of the lower connecting portion 22a by pressing or the like. Then, the adhesive 24 is cured. after that,
As shown in FIG. 7G, the lead wire 3 of the electrical component 30
1 is inserted into the insertion hole 28, and the lead wire 31 and both connecting portions 22a and 26a are electrically connected by a conductive substance 32.

Multilayer wiring board 34 manufactured by such method
Since both the connecting portions 22a and 26a are formed substantially flush with each other at the connecting portion between the lead wire and the wiring pattern in the electrical component insertion hole, one of the connecting portions 22a and 26a is formed on the same plane as in the embodiment shown in FIG. The adhesive 24 on the connecting portion 22a is easily and reliably peeled off, and the surface of the connecting portion 22a is clearly exposed.
Electrical connection with the conductive substance 32 is improved. Moreover, since there is almost no difference in level between the two connecting portions 22a and 26a, the electrical connection between them can be made extremely easily and reliably by the conductive material 32. Furthermore, there is no air accumulation during molten solder dipping, resulting in good solder finish, and the effect of thermal stress on the conductive material (due to gas, moisture, and air bubbles remaining in the adhesive 24) is reduced. The other configurations and operations are the same as those of the above embodiment, so detailed explanations will be omitted.

FIGS. 8 and 9 show still other embodiments of the present invention. Note that parts corresponding to those in FIG. 3 are given the same reference numerals. In this example, the lower layer conductive foil pattern corresponding to the first wiring pattern is a mere dummy pattern, and the electric component insertion hole 28 is formed in this conductive foil pattern 41, and the upper layer wiring pattern 2
6 connection portions 26a are formed. That is, the conductive foil pattern 41 does not necessarily need to be connected to other wiring patterns, but is a so-called dummy pattern that is separate and independent from the others. In this way, the presence of the dummy conductive foil pattern 41 under the connection portion 26a of the wiring pattern prevents degassing from the insulating base material 21 during molten solder dip for soldering the lead wire 31 of the electrical component 30. It can be shielded, the influence of degassing on the connection part 26a is avoided, and the adhesive strength of the connection part 26a by the copper foil is improved. Incidentally, the adhesive strength of copper foil decreases when affected by outgassing. In addition, since the solder resist layer 27 is deposited on the portions of the wiring pattern other than the connecting portion 26a, the adhesive strength of the wiring pattern does not decrease in those portions. This produces similar effects in the configurations shown in FIGS. 3 to 6 described above. Furthermore, even if the connection portion of the wiring pattern has a large area, the same effect can be expected by forming a dummy conductive foil pattern underneath.

In the above example, the insulating resin layer 23 is provided, but the insulating resin layer 23 is omitted and the adhesive 2 is used.
4 can also be used as an insulating layer that insulates between the upper and lower wiring patterns 22 and 26.

As described above, according to the present invention, the connection portion of the upper layer wiring pattern and the connection portion of the lower layer wiring pattern are configured to partially overlap or be adjacent to each other, so that the connection portion with the lead wire is When removing the adhesive, there is no accumulation of release liquid, and sufficient mechanical brushing can be performed, so that the adhesive can be removed reliably. As a result, the upper surface of the lower layer connection portion is clearly exposed, and electrical contact with the conductive material is improved.

In this case, both the connection parts of the first and second wiring patterns are laminated together using a semi-cured adhesive, so
The insulation layer between both connections is extremely thin (15 to 30 μm).
Therefore, they can be electrically connected very easily and reliably using a conductive material.

Furthermore, when a conductive substance is attached using a molten solder dip, air in the lower layer connection portion can easily escape, resulting in good soldering and good soldering.
Therefore, even when an automatic flow soldering device is used, for example, solder does not separate between the two connecting portions, and reliability is improved.

Furthermore, because the upper layer connection area is small, there is less gas, moisture, and air bubbles remaining in the adhesive underneath.
Therefore, the influence of stress caused by heat on the conductive material is reduced.

Furthermore, according to the present invention, since air escape is good, the connecting portion can be made smaller and a higher density wiring pattern can be formed.

In addition, using the solder resist layer and the second wiring pattern as a mask, the exposed semi-cured adhesive in the portion corresponding to the connection part of the first wiring pattern is removed to expose the connection part of the first wiring pattern. Therefore, it becomes possible to process this exposed portion into a fine and arbitrary shape.

[Brief explanation of drawings]

FIG. 1 is a partially cross-sectional perspective view showing an example of a conventional multilayer wiring board, FIG. 2 is a cross-sectional view of its connecting portion, and FIG. 3 is an embodiment of the method for manufacturing the multilayer wiring board of the present invention. FIG. 4 to FIG. 6 are plan views of main parts showing examples of the shapes of the connecting parts, and FIG. 7 is a perspective view of the process order showing another embodiment of the present invention. The partially sectional perspective view, FIGS. 8 and 9 are a sectional view and a plan view showing essential parts of still another embodiment of the present invention. 21 is an insulating base material, 22 and 26 are wiring patterns,
28 is an electrical component insertion hole, 30 is an electrical component, 31 is a lead wire, 32 is a conductive material, and 41 is a conductive foil pattern.

Claims (1)

[Claims] 1. A step of forming an insulating layer on an insulating substrate on which a first wiring pattern made of a first conductive foil is formed, excluding the connection portion of the first wiring pattern; , a step of laminating and combining a second conductive foil with a semi-cured adhesive applied to the back surface; and selecting the second conductive foil so as to partially overlap or be adjacent to the connecting portion of the first wiring pattern. forming a solder resist layer on the second wiring pattern except for a portion corresponding to both the connection portions of the first and second wiring patterns; using the solder resist layer and the second wiring pattern as a mask to remove the semi-cured adhesive exposed in the portion corresponding to the connection part of the first wiring pattern to connect the connection part of the first wiring pattern; A method for manufacturing a multilayer wiring board, comprising: exposing the first wiring pattern; and forming an electrical component insertion hole in a connecting portion of the first wiring pattern.