JPH06244528A - Manufacture of printed-wiring board - Google Patents

Abstract

PURPOSE:To provide the manufacturing method, of a printed-wiring board, wherein it can form a continuity hole in the board wish good accuracy and its productivity is high. CONSTITUTION:Parts in which a continuity hole is to be formed in metal thin- film layers 4, 5 formed on both faces of a board 1 formed in such a way that a glass cloth 2 has been impregnated with a resin 3 and hardened are removed. Then, the resin 3 on the board is removed by an atmospheric-pressure glow plasma etching operation 6, a hole is worked, a plating operation 7 is executed to the formed hole, and the continuity hole 8 is formed.

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 to a through hole which penetrates the front surface and the back surface or an arbitrary conductor layer and another conductor layer for electrically connecting the front surface and the back surface of the board. The present invention relates to a method of forming a non-penetrating conduction hole for establishing electrical conduction with.

[0002]

2. Description of the Related Art In a printed wiring board, a through hole is formed in the board as a means for establishing electrical continuity between the wiring pattern on the front surface of the board and the wiring pattern on the back surface of the board. Conventionally, a method of forming such a through hole is generally performed.

[0003]

By the way, as a method of forming a through hole in the above-mentioned substrate, a drill is generally used conventionally.

However, in such a method using mechanical drilling using a drill, stress is applied to the substrate during processing and shavings are generated. Therefore, this must be sufficiently removed before plating. A disconnection due to non-adhesion of plating in the through hole is likely to occur, resulting in lack of reliability. In addition, in response to the recent demand for higher functionality, higher functionality, and smaller size of electronic equipment, higher density packaging that houses multiple elements in a single standard package is required. In order to perform high-density mounting, it is necessary to form through holes with smaller and smaller diameters with high accuracy, but mechanical drilling with a drill has a limit in accuracy. Moreover, when forming a number of through holes in one substrate, mechanical drilling takes a very long time.

On the other hand, Japanese Patent Publication No. 2-57356 discloses CF ₄
And a method of forming a through hole by plasma etching in a reactive gas atmosphere containing O ₂ is disclosed. However, the etching rate is very slow, the processing takes a long time, the side etch amount is large, and the end portion in the through hole is large. There is a problem that the plating of the part is hard to be adhered, and the disconnection is likely to occur due to the non-adhesion of the plating.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a method of manufacturing a printed wiring board, which is capable of forming a conductive hole in a board with high accuracy and has high productivity.

[0007]

In order to achieve the above object, the present invention provides a through-hole or an optional through-hole for electrically connecting the front surface and the back surface of at least one layer of a printed wiring board. In a method of manufacturing a printed wiring board for forming a non-penetrating conduction hole for electrically connecting a conductor layer with another conductor layer, a portion of the metal thin film layer provided on the substrate where the conduction hole is formed is removed. Then, the substrate is subjected to hole forming processing by atmospheric pressure glow plasma etching, and then a conduction process is performed by plating to form a conduction hole.

The present invention will be described in detail below.

FIG. 1 is a sectional view showing an example of a method of manufacturing a printed wiring board according to the present invention in the order of steps.

As shown in FIG. 1A, the substrate 1 to be used
Is made by impregnating the glass cloth 2 with a resin 3 such as epoxy or polyimide and curing it, thereby giving a necessary material strength. Further, conductive metal thin film layers 4 and 5 such as copper are provided on both surfaces of the substrate 1, respectively. The metal thin film layers 4 and 5 respectively form wiring patterns on the front surface and the back surface of the substrate 1.

Next, as shown in FIG. 1B, the portions of the metal thin film layers 4 and 5 provided on both surfaces of the substrate 1 where the conductive holes are formed are removed by patterning by photoetching. That is, a photosensitive resin is applied or electrodeposited on the surfaces of the metal thin film layers 4 and 5, and then pattern exposure is performed, which is developed to form a resist pattern, and the exposed metal thin film layers are removed by etching. Finally, the metal thin film layers 4 and 5 are patterned by removing the resist pattern.

Then, as shown in FIG.
Perform the drilling process. The drilling process is performed by atmospheric pressure glow plasma etching 6 using the previously patterned metal thin film layers 4 and 5 as a mask.

FIG. 4 shows a schematic diagram of an apparatus for performing atmospheric pressure glow plasma etching. At least one of the two parallel plate electrodes 10 and 11 (see FIG.
Then, the anode 10) is provided with a solid dielectric 9 such as glass, ceramics, or plastic on the surface thereof,
The substrate 1 to be processed is placed on the cathode 11. Also,
A mixed gas of a rare gas and a reactive gas is used as the introduced gas, and the chamber is maintained at the atmospheric pressure by introducing the mixed gas. He or N is used as a rare gas.
A single gas such as e or Ar or a mixed gas can be optionally used, and He is particularly preferable. Further, as the reactive gas, a simple substance or a mixed gas of O ₂ , CF ₄ , CHF ₃ or the like can be arbitrarily used. Regarding the mixing ratio of the rare gas and the reactive gas, the rare gas concentration is preferably 65% or more.

As a result, stable glow discharge plasma is generated between the two electrodes 10 and 11 under atmospheric pressure, and the substrate 1 is etched by the generated active species.

According to this method, since the etching rate is high and the side etching amount is small, it is possible to perform highly accurate processing in a short time. The flow rate of the introduced gas, the high frequency output, etc. are arbitrarily set to appropriate values.

By such atmospheric pressure glow plasma etching 6, the resin 3 constituting the substrate 1 is removed, and the glass cloth 2 is not etched but is exposed as it is in the hole-processed portion.

Thereafter, as shown in FIG. 3D, the plated film 7 is applied to the holed portion to form the conduction hole 8.
As a plating method, a combination of electroless plating and electrolytic plating is particularly suitable. As described above, the glass cloth 2 is exposed and remains in the hole-processed portion, but there is a through hole (the portion indicated by reference numeral 2a in the same figure (c)) between the bundles of glass fibers in the vertical direction and the horizontal direction. Since it is formed, the plating film 7 is also formed inside this through hole, and as a result, the front surface and the back surface of the substrate 1 are electrically connected.

FIG. 2 is a cross-sectional view showing another example of the method for manufacturing a printed wiring board according to the present invention in the order of steps. The same portions as those in FIG.

In the present manufacturing process, instead of the substrate 1 using the glass cloth 2 described above, a substrate 1'made by impregnating and curing an aramid fiber 2'with a resin 3'such as epoxy or polyimide is used. (See FIG. 2 (a)). In addition,
Other fibrous polymer materials may be used as long as they are not aramid fibers and have appropriate rigidity.

Then, as shown in FIG. 2B, the portions of the metal thin film layers 4 and 5 provided on both surfaces of the substrate 1'for forming the conductive holes are patterned by photoetching in the same manner as described above. To remove.

Next, as shown in FIG. 3C, the hole forming process of the substrate 1'is performed by the atmospheric pressure glow plasma etching 6 described above. As is clear from the drawing, unlike the case where the glass cloth 2 is used, not only the resin 3'constituting the substrate 1 ', but also the aramid fiber 2'is completely removed by etching to form a through hole.

Thereafter, as shown in FIG. 3D, the through hole thus formed is provided with a plating film 7 by electroless plating or the like to form a conductive hole 8.

When the aramid fibers 2'and the like are used as described above, since the aramid fibers 2'and the like are completely etched and removed to form the through holes in the above-described hole-forming step by etching, the above-mentioned glass cloth is formed. There is an advantage that even a small-diameter conduction hole 8 in which the through hole 2a of the glass cloth 2 does not exist in the holed portion as in the case of using 2 can be formed without any problem.

Further, the present invention is not limited to the above-mentioned conduction holes penetrating through the front and back surfaces, but also non-penetrating conduction for electrically connecting any conductor layer of a plurality of conductor layers to another conductor layer. Holes (also commonly called VIA holes) can also be formed. FIG. 3 shows an example thereof, which includes the metal thin film layer 4,
4 ', 4 "at metal thin film layers 4 and 4' and 4 'and 4"
The case where a non-penetrating conduction hole 8'for forming electrical continuity is formed.

[0025]

According to the present invention, when forming a through hole in a substrate, the substrate is perforated by atmospheric pressure glow plasma etching.

As a result, even a conduction hole having a small diameter can be accurately formed, and since the etching rate is high, the time required for processing can be reduced.

Further, since the side etching amount of the drilling process is small, problems such as disconnection due to non-adhesion of plating in the conductive holes do not occur, so that the reliability is very high.

[0028]

The present invention will be described in more detail with reference to the following examples.

Example 1 A glass epoxy plate having a thickness of 100 μm obtained by impregnating a glass cloth with an epoxy resin and curing the same was formed on each side.
Photosensitive resin "Photo ED P-1000 (trade name)" on the front and back surfaces of a copper clad laminated substrate provided with a copper foil layer of 18 μm
(Manufactured by Nippon Paint Co., Ltd.) was adhered by electrodeposition, a pattern of predetermined circular holes was baked on this by a mask exposure method, and developed with a sodium metasilicate solution to remove the above-mentioned photosensitive resin in the exposed portion. Next, the exposed copper foil is etched with a ferric chloride solution, the remaining photosensitive resin is peeled off with a 5% sodium hydroxide solution, washed with water, and dried to form conductive holes on both surfaces of the glass epoxy plate. A pattern having a hole diameter of 0.6 mm was formed by removing the copper foil in a portion.

Next, the prepared sample was placed in the chamber of the plasma etching apparatus having the structure shown in FIG. 4, and the substrate was perforated by plasma etching under the following conditions. At this time, the etching rate of the epoxy resin layer of the substrate was about 0.5 μm / min. Although the glass cloth was not etched, a plurality of through holes each having a size of about 0.1 mm square were formed between the yarns (a bundle of glass fibers). Processing conditions Introduced gas: O ₂ (flow rate 50 SCCM) + He (flow rate 2000
SCCM) High frequency output: 90KHz 50W

Thereafter, the sample was taken out of the chamber, pretreated, and then immersed in a plating solution "Sulcup (trade name)" (manufactured by Uemura Kogyo Co., Ltd.) to perform electroless copper plating (55 ° C, 3 minutes). ), And a conductive hole having a plating thickness of about 30 μm was formed by electrolytic copper plating.

Example-2 The same procedure as in Example-1 was performed on both surfaces of a copper-clad laminate using aramid fiber "Kevlar (trade name)" (manufactured by DuPont) instead of the glass cloth in Example-1. A pattern was formed by removing the copper foil in the portion where the conduction hole is formed.

Next, this sample was subjected to etching under the same conditions as in Example 1 to perforate the substrate. The etching rate of the substrate at this time was about 0.5 μm / min, and the aramid fiber was completely removed by etching to form a through hole.

Then, as in Example-1, the through holes thus formed were plated with copper to form conductive holes.

Example 3 An aramid epoxy plate made by impregnating an aramid fiber (described above) with an epoxy resin and curing it and a copper foil layer were sequentially laminated as shown in FIG. Patterns (the positions of the patterns on the front surface and the back surface are different) were formed on the front surface and the back surface of the substrate, respectively, in the same manner as in Example 1 from which the copper foil in the portions where the conductive holes were formed was removed.

Next, this sample was etched under the same conditions as in Example 1 to perforate the substrate. At this time, a non-through hole was formed from each of the front surface and the back surface of the substrate to the middle copper foil layer (see FIG. 3).

After that, in the same manner as in Example-1, the formed holes were plated with copper to form conductive holes (VIA holes).

[0038]

As described above in detail, according to the present invention, the portion of the metal thin film layer which forms the conductive hole is removed, and then the substrate is perforated by atmospheric pressure glow plasma etching. By conducting a conductive process by plating after that, a conductive hole for electrically connecting the front surface and the back surface of the substrate is formed, so that even a small-diameter conductive hole can be accurately formed. You can do it. In particular, due to recent high-density mounting, it is required to form conductive holes of smaller diameter with higher precision, and the present invention is an excellent method that meets this requirement.

Moreover, since the etching rate is high, the time required for boring the substrate can be shortened.
Productivity is significantly improved.

Further, since the side etching amount of the hole forming process of the substrate is small, there is no problem such as disconnection due to non-adhesion of plating in the conduction hole, so that the reliability of the manufactured product becomes very high.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a method for manufacturing a printed wiring board of the present invention in the order of steps.

FIG. 2 is a cross-sectional view showing another example of the method for manufacturing a printed wiring board of the present invention in the order of steps.

FIG. 3 is a cross-sectional view showing another example of the method for manufacturing a printed wiring board of the present invention in the order of steps.

FIG. 4 is a schematic diagram of a plasma etching apparatus used in the present invention.

[Explanation of symbols]

 1, 1'Substrate 2 Glass cloth 2'Aramid fiber 3,3 'Resin 4,5 Metal thin film layer 6 Plasma etching 7 Plating film 8 Conducting hole 9 Solid dielectric 10 Anode 11 Cathode

Claims (3)

[Claims] 1. A conductive hole penetrating through the front surface and the back surface for electrically connecting the front surface and the back surface to at least one substrate constituting a printed wiring board or electrically connecting the conductor layer to another conductor layer. In a method of manufacturing a printed wiring board for forming a non-penetrating conductive hole for removing a portion of the metal thin film layer on the substrate where the conductive hole is formed, and then punching the substrate by atmospheric pressure glow plasma etching. The method for producing a printed wiring board is characterized in that the conducting hole is formed by performing a conducting treatment by plating. 2. The method of manufacturing a printed wiring board according to claim 1, wherein the substrate is a glass cloth impregnated with a resin. 3. The method for manufacturing a printed wiring board according to claim 1, wherein the substrate is a fibrous polymer material such as aramid fiber impregnated with a resin.