JPS5830190A - Method of producing printed board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a high-density printed board with a pattern width of 100P or less.

Printed boards are required to have thinner patterns as integrated elements become more highly integrated, and to meet this demand, the manufacturing of printed boards is also shifting from subtractive to additive methods. A thin copper foil is formed on the entire surface of the board by electroless copper plating, a photoresist pattern is formed on it using a positive mask, and then a thick layer of copper is selectively applied to the areas where there is no resist by electrolytic copper plating. The semi-additive method has the advantage of excellent productivity due to the short plating time, but has the disadvantage of large variations in plating thickness. In particular, when the pattern width is less than 100 PL, the width may be three times or more in thin and thick areas, causing problems in pattern strength and the like. On the other hand, the full additive method, in which a photoresist pattern is formed using a positive mask on an insulating plate containing a plating catalyst, and then the areas without resist are selectively made conductive by electroless steel plating, has the disadvantage of a long plating time. However, there is an advantage in that the variation in plating thickness is small and a conductor pattern with a relatively uniform thickness can be formed regardless of the size of the substrate or the density of the pattern.

However, as the pattern width becomes around 50 pm, the direct current resistance of the pattern increases, so the plating thickness needs to be 50 μm or more in view of the electrical properties of the printed board.

In this case, the resist film; the turn is a pattern with a high shape ratio in which the thickness of the resist is larger than the pattern width, but when electroless copper plating is applied on a resist pattern with such a high shape ratio, it is difficult to There is a problem in that it is difficult to remove the generated hydrogen gas from the resist pattern. For this reason, the conductor turns were porous, had weak mechanical strength, were easily broken, and had the drawbacks of high DC resistance.

The purpose of the present invention is to solve these drawbacks by forming a resist pattern with a high shape ratio using a photoresist on a portion other than the conductor pattern formed on an insulating substrate, and then spraying an electroless plating solution onto the substrate. An object of the present invention is to provide a method for thickly depositing metal on a conductive pattern.

That is, to summarize the present invention, the present invention provides a method for manufacturing a printed board in which a conductive pattern formed on an insulating substrate is made into a thick metal pattern by electroless plating. Manufacturing a printed board characterized by comprising a step of forming a plating resist pattern on other parts, and a step of spraying an electroless copper plating solution onto the substrate on which the plating resist is formed to deposit copper on the conductor pattern. Regarding the method.

Hereinafter, the present invention will be specifically explained based on the drawings.

FIG. 1 is a cross-sectional view of a substrate at each step in the printed board manufacturing method of the present invention.

FIG. 1(a) shows a conductor pattern (2) on an insulating substrate (1).
), a land (2'), and a through hole (3) are formed. As the insulating substrate (1), an insulating board made of glass-epoxy, glass-polyimide, etc., or an insulating board coated with an adhesive can be used.

Is the conductor pattern (2) formed on the insulating substrate (1) by electroless plating or vacuum evaporation on the entire surface of the copper foil? After forming, photo etching is performed. Using a copper-clad laminate as a starting material, conductor patterns (2
), but in this case, it is preferable to use an ultra-thin steel foil of 5 µln in order to form a fine line pattern.

FIG. 1(1)) is a sectional view of a photoresist film (4)'ff- formed, and in order to have a film thickness of 5QP or more, a dry film photoresist is preferable. Figure 1 (
C) is a cross-sectional view irradiated with ultraviolet light through a positive mask (5) fe, where the positive mask (5) is a conductor pattern (2).
f. It is used as a positioning mark and is precisely aligned. The portion of the conductor pattern (2) outside the upper body is cured by light irradiation and becomes insoluble in the solvent. Figure 1(d) shows that the resist film on the conductor pattern (2) is dissolved by development.
FIG. 6 is a cross-sectional view of a resist film formed with a turn (6). FIG. 1(e) is an fcvgT plane view in which copper (7) and (7') are thickly deposited on the conductor pattern (2) by spraying an electroless copper plating solution. FIG. 1(f) is a sectional view of the printed board obtained by removing the resist pattern.

In the present invention, the conductor pattern (2) plays a role as a plating catalyst, and the reason why the conductor pattern (2) was used as a base for t-electroless copper plating is as follows.

In the general fully additive method, noble metals such as Pi and Ag are used as plating catalysts, but these are only attached to the substrate in the form of fine particles and are not firmly held on the insulating substrate.

In the present invention, in order to remove hydrogen gas generated during copper deposition from the resist pattern, an electroless steel plating solution is strongly injected onto the insulating substrate. Since the copper is not retained in the plating solution, it is washed away by the plating solution and no copper precipitation occurs. In addition, the leaked PA particles promote the reduction of copper during electroless copper plating, which poses a serious problem of significantly shortening the life of the electroless copper plating solution. On the other hand, when plating a conductive pattern (2) with a thickness of 1 to 5 P as in the present invention, the conductive pattern is firmly held on the substrate as a metal foil, so the plating solution is sprayed strongly. Copper precipitates without flowing out, making it possible to build up the thickness.

Next, the electroless copper plating apparatus used in the present invention will be explained. FIG. 2 is a schematic sectional view showing an example of a plating apparatus used in the present invention.

The electroless copper plating solution (9) below the plating tank (8) is sucked by the pump αQ, and is passed through the filter α◇ and the liquid management device (
6) and is sprayed by a nozzle onto the substrate C14 on which the resist pattern is formed. Liquid management device 0 humiliation is,
Performs liquid analysis, replenishment and temperature control.

The nozzle 01 is one in which the injected copper plating solution forms a full cone shape, and can be oscillated as necessary.

Spray pressure is 1.0kg/cm2 to 2.0'9
It can be changed up to 42. 9/1 to pressure 1.0
If the ratio of resist thickness/pattern width is rn2 or less, hydrogen gas between the resist patterns cannot be completely removed, and the deposited copper becomes porous, resulting in poor reliability. Further, if the pressure is 2.0 cm or more and the thickness exceeds 9 cm, the copper deposition rate is slow, and the conductor pattern may dissolve in some cases.

As the electroless copper plating solution (9), any commercially available solution can be used, but an electroless copper plating solution for thick coating is preferred from the viewpoint of the plating deposition rate.

Examples according to the present invention will be described below, but the present invention is not limited thereto.

Example 1 1.6 m thick glass-epoxy laminate with 0.5 mm diameter
After drilling holes, the surface was roughened using chromic acid-sulfuric acid. Next, P (1) was deposited on the substrate as a plating catalyst using a commonly used surface activation method, and then the copper foil was immersed in an electroless plating solution (OP-78 manufactured by Silapray Co., Ltd.) to a thickness of approximately 3 μm. was formed on the entire surface of the substrate.By photo-etching the copper foil, 50P
A conductor pattern with a width of 1.5 mm and a land with a diameter of 0.6 ssφ were formed on the substrate.Next, a 5oPL thick dry film negative photoresist (Liston 730FR manufactured by DuPont) was laminated on the substrate using a hot roll laminator. Ta.

Next, a positive mask was brought into close contact with the resist film, and ultraviolet light was irradiated. The exposure energy was 100/am. The positive mask had a black pattern with the same width of 50 IIrrL as the conductor pattern, and the conductor pattern was used as an alignment mark for accurate alignment. The resist film on the conductor pattern was dissolved by development using trichloroethane, and a resist pattern having a resist thickness/pattern width ratio of 1 was formed. The pattern profile was better when the development was carried out in a solvent placed in an ultrasonic generator than by spray development. Place the substrate in the apparatus shown in Figure 2 and apply the plating solution (OF-78) at a pressure of 1.2 kg/cm2.
Then, copper was deposited to a thickness of 50 μm on the conductor pattern by spraying the substrate with VC at a temperature of 40° C. for 12 hours. Strip the resist pattern with methylene chloride,
A printed board with a pattern width of 50 μm, a plated steel thickness of 50 μm, a through hole diameter of 0.4 fin φ, and a land diameter of 0.6 wφ was obtained. Although the resist pattern was peeled off here, it can also be left on the substrate and used as an insulating layer. The obtained printed board was able to accommodate all the patterns accommodated in the 8 layers of a printed board (conductor pattern width: 150 InIL) according to current technology due to the thinning of the conductor pattern and the miniaturization of the through holes.

Example 2 To form a resist pattern with a resist thickness/pattern width ratio of 2, the entire conductor pattern was formed on the substrate in the same manner as in Example 1, and the dry film lamination conductor pattern and positive mask were positioned. After irradiating with ultraviolet light,
The same dry film-like negative resist film was laminated using a hot roll laminator onto the first resist film that had been irradiated with ultraviolet light without being developed. Using the same positive mask, it was aligned with the conductor pattern, brought into close contact with the second layer resist film, and irradiated with ultraviolet light. The exposure energy of the first layer resist film is 80/c as described in Example 1.
rn2, but the exposure energy for the second layer resist film was 1001nJ42, the same as in Example 1, and fc6.
After irradiating the first and second resist films with light, the first and second resist films on the conductor pattern are simultaneously developed and dissolved, so that the pattern width is 50P and the resist thickness is A resist pattern with a high shape ratio of 1 oo.m in diameter was obtained. Next, using the apparatus shown in FIG. 2, an electroless copper plating solution (CP-78 manufactured by Silapray Co., Ltd.) was sprayed onto the substrate to deposit copper with a thickness of 100 P on the conductor pattern.

Since the shape ratio (resist thickness/pattern width ratio) is 2, the pressure must be 1.8 to completely remove hydrogen gas.
The plating time was 55 hours at a plating temperature of 40°C.The resist pattern was peeled off with methylene chloride, and the pattern width was 50 μm1.
Plated copper thickness 100μm 1 through hole diameter Q, 5mφ,
A high-density printed board with a runt diameter of 0.6 mm was obtained. Although this printed board has a thin line pattern, the plating is thick, so even after 1,000 cycles of thermal shock (-65°C x 50 minutes ← → 125°C x 30 minutes) test, there were no problems such as disconnections and it was highly reliable. .

Example 3 Pd '1l on At203 ceramic plate (1 piece thick)
After applying an adhesive containing l- to a thickness of about 10P, the surface is roughened with chromic acid-sulfuric acid, and a layer of about 2μ is applied on the adhesive.
Form a copper foil of m. The copper foil was photoetched to form a conductor pattern with a pattern width of 25Pn.

Next, a 25 μm thick dry film negative resist (
Listono 1010 (manufactured by DuPont) was bonded onto a substrate using a hot roll laminator to form a first resist film. After exposure through a positive mask in the same manner as in Example 2, a second resist film was formed without development, and exposure was performed once again through a positive mask. The exposure energy was 40 tnJA for the first resist film.
, the second layer resist film was 50"0x12. After exposure, the first and second layer resist films were developed simultaneously to form a pattern width of 25PrrL1 and resist thickness of 50I.
A resinet pattern with a shape ratio of trrL of 2 was formed avoiding the conductor pattern. Plating copper having a thickness of 50 μm was formed on the conductive pattern using the plating apparatus shown in FIG. 2 under the conditions of a pressure of 2.0 ra and a temperature of 40° C. for 1 hour and 20 hours.

The resist pattern was peeled off with methylene chloride to form a printed pattern on a ceramic plate with a pattern width of 25 μm and a plated copper thickness of 50 μm. Compared to a ceramic printed board formed by screen printing using conductive ink, a high-density printed board with a fine line pattern and low DC resistance was obtained.

As explained above, the method for manufacturing a printed board according to the present invention uses a conductor pattern as a plating catalyst, and injects an electroless copper plating solution using a resist pattern with a high shape ratio formed avoiding the conductor pattern as a plating resist. Since the plated copper is formed on the conductor pattern, the plated copper can be formed thickly without becoming porous.
Although the pattern is a thin line, it has excellent reliability and electrical characteristics, and has the advantage of being able to produce solid printed boards.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(f) are cross-sectional views of the substrate at each step in the printed board manufacturing method according to the present invention. FIG. 2 is a schematic sectional view showing an example of an electroless copper plating apparatus used in the present invention. 1: Insulating substrate, 2: Conductor pattern, 2': Land, 3 Varnish through hole, 4 Ni resist film, 5: Positive mask, 6:
Resist pattern, 7.7': Plating copper, 8: Plating tank, 9: Electroless copper plating solution, 10: Pump, 11: Filter, 12: Liquid management device, 13: Nozzle, 14 Resist pattern Formed substrate patent applicant Hiroshi Moto, agent of Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Scope of Claims] 1. In a printed board manufacturing method in which a conductor pattern formed on an insulating substrate is made into a thick metal pattern by electroless plating, the conductor pattern is formed on a portion other than the conductor pattern on the insulating substrate. A method for producing a printed board, comprising the steps of forming a plating resist and depositing copper on a conductor pattern by spraying an electroless steel plating solution onto the substrate on which the plating resist is formed. 2. The method for manufacturing a printed board according to claim 1, wherein in the step of forming the plating resist, the conductive pattern is used as an alignment mark for a positive mask.