JPH07297519A - Manufacture of wiring board - Google Patents

Abstract

PURPOSE:To easily manufacture a high density wiring board having a fine hole by laminating a metallic foil on a front and a rear of a prepreg which is punched in advance and by pressurizing, heating and integrating them. CONSTITUTION:A hole 2 is formed in a glass woven fabric/epoxy resin prepreg 12 by punching processing, a copper foil 11 is laminated on both sides thereof and they are pressurized and heated. After a photosensitive dry film is laminated, it is exposed and developed for forming an etching resist pattern 32. A copper foil of the same place on both sides of a board is etched simultaneously at a diameter of 0.5mm or less in a hole part formed in the prepreg which is filled with resin in the pressurizing and heating process. Thereafter, it is immersed in concentrated sulfuric acid, a copper foil is etched and an exposed resin filled part is dissolved. Resin of the resin filled part is completely dissolved and a hole 33 is made to pass through. Thereafter, a plating layer 4 is formed. Then, after a photosensitive dry film is laminated, it is exposed and developed for forming an etching resist pattern 5, and wiring is formed by etching.

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 high-density wiring board.

[0002]

2. Description of the Related Art As electronic devices become lighter, thinner, shorter, smaller, and more sophisticated, the installation space for wiring boards is becoming narrower, and wiring boards are required to be even higher in density and thinner. In particular, for liquid crystal and semiconductor mounting, thinning and high density are advancing, and designs with a size of several centimeters square and a thickness of 0.1 to 0.2 mm are emerging. There is. In such a case, the line width and the space width are about 50 to 100 μm, and the diameter of the connecting hole is extremely small, 0.1 to 0.2 mm. For a high-density wiring board, it is common to use a base material or the like reinforced with an epoxy resin by a glass cloth and to make a hole with a drill. In order to cope with this fine drilling, a drill having a diameter of 0.3 mm or less has begun to be put into practical use. In addition, a high-density wiring board in which micro holes are formed by laser using a stacking method is also proposed. In addition, recently, by dissolving the resin layer,
The method of making a hole is also proposed.

[0003]

By the way, in the case of forming fine wiring, from the viewpoint of dimensional stability of the base material, mechanical strength required for processing, cost, etc., an epoxy resin base reinforced with woven or non-woven fabric is used. Fiber-reinforced resin substrates such as wood are suitable. However, when drilling a hole with a minute diameter, the reinforcing fiber bends the course of the drill, which deteriorates the hole position accuracy, and the drill easily breaks, and it is necessary to reduce the feed rate of the drill. Even if it is done, however, the wear of the drill is so severe that it is necessary to limit the number of holes to be drilled by one drill to a small number. In addition, when a resin base material reinforced with glass fiber or the like is used, it has an advantage that the strength of the support is high, but when the distance between holes for wiring connection is narrow and there is a potential difference between the holes, it is exposed on the hole wall. There was a problem that the metal of the hole wall migrates through the interface between the glass fiber and the resin, and causes insulation deterioration in a long period of time.

In the case of laser drilling, if there are glass fibers in the substrate, in addition to the problem of migration as described above, it is difficult to remove the glass portion by laser irradiation, and the glass fibers remain unburned around the holes. There were challenges. There is also a problem that heat is transmitted to the periphery of the hole through the glass fiber and damages the resin. For this reason, when laser drilling is used, a method has been proposed which is mainly applied to a stacking method in which insulating layers are stacked only with resin. However, in the case of the stacking method, it is difficult to apply it to a thin wiring board having a total thickness of 0.1 to 0.2 mm because a supporting base material is required at first. Unavoidably,
When an extremely thin support base material is used, there is a problem that handling is poor and processing is extremely difficult because the strength of the entire support is low. Further, when the resin layer is melted and punched, if the base material contains a material such as glass fiber that is difficult to dissolve, it takes time and effort to remove it, resulting in an increase in cost. Was not applied to. In fact, stacking resin insulation layers,
Next, its use was limited, such as making a connection hole between layers.

[0005]

A method for manufacturing a wiring board according to the present invention comprises a step of forming a hole at a predetermined position of a prepreg made of a woven cloth, a nonwoven cloth and a thermosetting resin, and superposing a metal foil on the front and back of the prepreg. , A step of filling the holes of the prepreg with resin at the same time as pressure heating and integration, a step of etching the front and back of the metal foil on the surface of the resin-filled portion in a desired shape,
The method is characterized by including a step of chemically dissolving and removing the exposed resin-filled portion and a step of forming wiring.

In this case, after the step of chemically dissolving and removing the filled portion of the resin, a step of mechanically or chemically removing the resin residue can be provided.

As the woven cloth and the non-woven cloth, a glass woven cloth and a glass non-woven cloth can be used, and the thermosetting resin mainly contains an epoxy resin-based resin, an epoxy acrylate resin-based resin, and a phenol resin. A resin or the like can be used.

Further, it is possible to provide a step of forming a metal layer on the hole wall after the exposed resin-filled portion is chemically dissolved and removed.

The shape in the step of removing the metal foil on the surface of the resin-filled portion by etching can be various shapes depending on the purpose, and migration is particularly problematic in the prior art. Holes having a diameter of 5 mm or less can be used, which is preferable in order to increase the density of wiring.

In the process of chemically dissolving and removing the resin-filled portion, sulfonic acids can be used for dissolution and removal,
As such sulfonic acids, sulfuric acid or alkyl sulfonic acid can be used.

The desired shape is effectively applied to a high-density wiring board, and the hole diameter is generally 0.5 mm or less.

In the present invention, the prepreg can be punched with a punch or a router, and various reinforcing fibers such as glass and Kevlar can be used, but glass is particularly suitable from the viewpoint of cost. The resin used for the prepreg at this time is an epoxy resin, a phenol resin, an epoxy acrylate resin, or a modified resin thereof,
Particularly suitable. Epoxy resin, which has comprehensively excellent properties such as heat resistance, mechanical properties, electrical properties, and chemical resistance, is suitable for wiring boards that require high properties. Although the properties are slightly lowered, the resin is inexpensive, and the phenol resin, which is often used for wiring board applications, is suitable for a low-cost wiring board. Further, the use of an epoxy acrylate resin has an advantage that the resin dissolution rate is fast and the processing time can be shortened.

The number of prepregs to be used is one or two, which is suitable for manufacturing a thin wiring board, but is not limited thereto. A metal foil is laminated on the front and back of the prepreg that has been subjected to the hole processing, and pressure and heating are integrated. At this time, the resin of the prepreg flows and fills the holes that have been opened in advance. In order to prevent air bubbles from being trapped in the resin-filled portion, they may be pressure-heated and integrated under vacuum. The thickness of the metal foil is determined by the density of the wiring and the cost of the metal foil.
Generally, a thickness of 5 to 50 microns can be used,
In particular, when forming a high-density wiring having a wiring width of 100 μm or less, it is preferable to use a metal foil having a thickness of 5 to 20 μm. Next, a hole for wiring connection is made in the resin filled portion. The hole diameter is determined by the purpose and cost.

When a hole for wiring connection is formed by using this method, it is most effective if it is applied to a hole having a diameter of 0.05 to 0.5 mm. If the diameter is less than 0.05 mm, it will be difficult to align the front and back metal foils for removal.
When drilling holes having a diameter of 0.5 mm or more, the wiring density is lower than the wiring density targeted by the present invention, and the hole spacing is wide, so that the reliability is generally not so severe. . In such a case, it is more cost effective to directly drill a hole in the conventional fiber reinforced resin layer. The larger the number of holes, the greater the effect of the present invention. In addition, such a resin filling part for making a hole for wiring connection, if necessary,
A plurality of substrates may be provided.

Next, the wall surface of the wiring connection hole is plated. For the plating, any of electroless plating, electroplating, and a combination of these may be used. After that, wiring is formed by a known method. Known examples of wiring formation include a method of forming wiring by using a photosensitive resin varnish, a photosensitive electrodeposition resin, a photosensitive dry film, or metal plating such as solder or nickel as an etching resist. Note that the hole shape is not limited to a circular shape, and may be a rectangular shape or another irregular shape.

[0016]

In the present invention, the metal foil is placed on the front and back of the pre-drilled prepreg, and the resin is flowed and filled in the hole by heating and unifying the prepreg. Therefore, the resin in the hole filling portion can be easily dissolved and removed. Further, the hole shape is not limited to a circular shape as in the case of using a drill and can be freely determined, and a die is not required for each punching pattern like punching. . Moreover, a plurality of holes can be simultaneously formed at one time. Furthermore, since reinforcing fibers can be used and the supporting strength of the substrate is obtained, the holes are filled with resin and the fibers are not exposed, so when used as connection holes for wiring The generation of migration along the fibers and the trapping of various treatment liquids at the interface between the fibers and the resin are suppressed.

[0017]

【Example】

(Example 1) (1) As shown in FIG. 1 (a), GEA-67 which is a 0.2 mm thick glass woven cloth / epoxy resin prepreg.
N (Hitachi Chemical Co., Ltd., trade name) is punched to form a hole with a width of 30 mm and a length of 50 mm.
A copper foil having a thickness of 18 microns is laminated, and as shown in FIG. 1 (b), 25 kgf / cm ² , 170 ° C., 0.5 To
It was heated under pressure under the condition of rr for 60 minutes. (2) Phototec H-K450 (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a photosensitive dry film having a thickness of 50 μm, is laminated, exposed and developed to form a resist pattern for etching (see FIG. 1 (c ))), The copper foil at the same location on both sides of the substrate is etched at the same location on the both sides of the substrate at the same time on the hole portion formed in the prepreg, which is filled with the resin in the previous pressure and heating step and has a diameter of 0.2 mm. However, the mutual distance between the etching points was set to 0.5 mm. After this, 98
% Concentrated sulfuric acid to etch the copper foil to dissolve the exposed resin-filled portion. In this resin-filled portion, the resin was completely dissolved in about 3 minutes, and the hole penetrated (shown in FIG. 1D). After that, a catalyst was applied with HS-201B (manufactured by Hitachi Chemical Co., Ltd., trade name), electroless copper plating was performed with CUST-201 (manufactured by Hitachi Chemical Co., Ltd., trade name), and then electrolytic copper sulfate plating was used to increase the thickness. A plated layer having a thickness of about 7 μm was formed (shown in FIG. 1 (e)). (3) After laminating Phototec H-K450 (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a photosensitive dry film having a thickness of 50 microns, it is exposed and developed to form a resist pattern for etching, and wiring is performed by etching. It was formed (shown in FIG. 1 (f)).

Example 2 (1) A substrate was prepared in the same manner as in Example 1. (2) In the same manner as in Example 1, dissolve the resin in the filling part,
A plating layer was formed. (3) Electrodeposition resist No. 376 (trade name, manufactured by Kansai Paint Co., Ltd.) was formed under the conditions of 60 mA / dm2 and 250 seconds. After forming 510 (manufactured by Kansai Paint Co., Ltd., trade name) under the condition of 130V for 70 seconds,
After exposure and development, a resist pattern for etching was formed and etching was performed to form wiring.

COMPARATIVE EXAMPLE 1 GEA-67N (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a glass woven cloth / epoxy resin prepreg having a thickness of 0.2 mm, has no holes.
The same copper foil as in Example 2 was laminated on both sides of the prepreg.
After that, pressure heating was performed under the same conditions as in Example 2. Other steps were performed in the same manner as in Example 2 to obtain a wiring board.

(Test) (1) Electrolytic Corrosion Test Under conditions of 85 ° C. and 85% RH, a voltage of DC100V is applied to a gap of 0.5 mm (hole wall interval is 0.2 mm).
It was applied between the through-holes opened at, and the time when the connection resistance became 10 6 ohm or less was examined. as a result,
In Comparative Example 1, the maximum time was 200 hours or less, and the average time was 80 to 100 hours. On the other hand, the insulation of the substrates of Examples 1 and 2 did not deteriorate even after 500 hours.

(2) Connection reliability As a result of a thermal shock test (alternate repetition of 125 ° C./30 minutes and −65 ° C./30 minutes), in each of Examples 1 and 2 and Comparative Example 1, after 300 cycles It was found that there was no abnormality when the change rate of the connection resistance was 10% or less.

(3) Heat resistance As a result of being floated in a solder bath at 260 ° C. for 30 seconds, it was found that there was no abnormality such as peeling in each of Examples 1 and 2 and Comparative Example 1.

[0023]

According to the present invention, a high-density wiring board having fine holes can be easily manufactured. Moreover, the insulation reliability is excellent as compared with the conventional one using the fiber-reinforced base material.

[Brief description of drawings]

1A to 1F are cross-sectional views in each step for explaining an embodiment of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display location // C08L 61:06 63:00 63:10 (72) Inventor Atsushi Nishimura Ogawa, Shimodate City, Ibaraki Prefecture 1500, Hitachi Chemical Co., Ltd. in Shimodate Research Laboratory (72) Inventor Naoyuki Urasaki 1500 Ogawa, Shimodate, Ibaraki Pref. 1500 Shimodate Research Laboratory, Hitachi Chemical Co., Ltd. (72) Inoue Iwasaki 1500 Ogawa, Shimodate, Ibaraki Hitachi Kasei Industry Co., Ltd. Shimodate Factory

Claims (10)

[Claims] 1. A step of forming a hole at a predetermined position of a prepreg made of a woven fabric, a nonwoven fabric and a thermosetting resin, a metal foil is superposed on the front and back of the prepreg and integrated under pressure and heating, and at the same time, the hole of the prepreg is made into a resin. Including the step of filling with, the step of etching the metal foil on the surface of the resin-filled portion in a desired shape by etching both front and back, the step of chemically dissolving and removing the exposed resin-filled portion, and the step of forming wiring. A method of manufacturing a wiring board, characterized by: 2. The method for manufacturing a wiring board according to claim 1, further comprising a step of mechanically or chemically removing the resin residue after the step of chemically dissolving and removing the resin-filled portion. 3. The method for manufacturing a wiring board according to claim 1, wherein the woven cloth and the non-woven cloth are glass woven cloth and glass non-woven cloth. 4. The method for manufacturing a wiring board according to claim 1, wherein the thermosetting resin is a resin mainly composed of an epoxy resin. 5. The method for manufacturing a wiring board according to claim 1, wherein the thermosetting resin is a resin mainly composed of an epoxy acrylate resin. 6. The method of manufacturing a wiring board according to claim 1, wherein the thermosetting resin is a resin mainly composed of a phenol resin. 7. The wiring according to claim 1, further comprising a step of chemically dissolving and removing the exposed resin-filled portion and then forming a metal layer on the hole wall. Board manufacturing method. 8. The method according to claim 1, wherein the shape in the step of removing the metal foil on the surface of the resin-filled portion by etching is a hole having a diameter of 0.5 mm or less. The method for manufacturing a wiring board according to any one of the above. 9. The method for manufacturing a wiring board according to claim 1, wherein in the step of chemically dissolving and removing the filled portion of the resin, the dissolving and removing is performed with a sulfonic acid. 10. The method for manufacturing a wiring board according to claim 9, wherein the sulfonic acid is sulfuric acid or an alkyl sulfonic acid.