JPS58204595A - Method of producing printed circuit 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 through-hole printed wiring board, and particularly to a method for manufacturing a printed wiring board that has good insulation between conductors and is suitable for high density.

Printed wiring boards are manufactured by various methods.

However, as printed wiring boards become more densely interconnected, there are demands for high-precision A-line conductor circuits, miniaturization of surface conductive holes, and improved insulation properties between conductors.

Conventionally, high-density wiring boards are produced by forming an etching-resistant resist on a double-sided steel-clad laminate by photoetching or screen printing, forming a desired conductor circuit by etching, and then attaching it to a predetermined position through a land (pad). Holes are drilled in the area, immersed in an activator for electroless copper mating such as stannous chloride or palladium chloride solution, and dried.Then, the desired soldering is done by screen printing on all but the planned areas (lands) to prevent plating. It was manufactured by printing a resist and performing electroless steel plating to form through holes.

However, in the above method, the conductor circuit is formed from a steel-clad laminate with a uniform copper foil thickness, which is very advantageous in making the wiring pattern thinner and more precise. Because palladium, which serves as a catalyst for chemical steel plating, is adsorbed on the entire surface of the board, it is difficult to use as a high-density wiring board, that is, a printed wiring board for electronic equipment, in terms of insulation properties between conductor circuits.

Further, from the viewpoint of reliability, the thickness of the plating film formed on the conductive hole usually needs to vary by about 3Qlffn. For this reason, the gravel plate is immersed in a highly alkaline (pH 12 to 16) chemical steel plating solution for 10 to 20 hours, which prevents the plating solution from penetrating through the pinball portions of the plating resist film or areas where the film is thin. Discoloration of the conductor and peeling of the resist film occurred, and as a result, soldering caused defective wiring boards.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a method for manufacturing a high-density printed wiring board with excellent insulation between conductor circuits.

In order to achieve the above object, a method for manufacturing a printed wiring board according to the present invention uses an insulating substrate on which a conductor circuit is previously formed, and 1. After drilling holes in the predetermined locations on the board, soldering involves a process of forming a resin layer, leaving the planned areas, and a process of applying chemical steel plating pre-treatment to the entire surface. The gist is that it consists of a process of forming a liquid solder 1 resist, and a process of forming a chemical steel plating on the exposed inner wall of the hole and the conductor in the area where soldering is planned. do.

According to the present invention, the insulation properties between conductive circuits are improved by forming an etching resist on a double-sided laminate, and after etching this etching resist to form a desired conductive circuit, This problem can be solved by a method that does not allow plating nuclei such as palladium, which acts as a catalyst for chemical steel plating, to adsorb or remain on the etched surface (insulating material surface) of the unnecessary steel foil portion. Roughly speaking, soldering resist (solder resist) is used to form only the intended part and the inner wall of the conductive hole with chemical steel plating. Discoloration or swelling due to poor adhesion may occur. As a result of various studies, it has been found that increasing the film thickness is effective for improving the plating solution resistance of these resists. In other words, etching is performed on a double-sided copper-clad laminate using a known method. After forming the desired conductor circuit by etching, holes for front and back conductivity are drilled at predetermined positions. Next, a resin layer is formed on the entire surface of the board, leaving the planned areas for soldering, and an activation treatment for chemical steel plating is performed. Next, a plating-resistant resist is formed on the resin layer (other than the soldering part), and then chemical steel plating is performed.

In this method, chemical copper plating is selectively deposited only on the inner wall of the hole where the activated surface is exposed and on the planned area for soldering. Furthermore, an activator (palladium) that lowers the insulation between conductors is fixed between the resin layer and the double film of Tsurugu resist. In addition, since the solder resist film is a double layer, there are no pinholes, and the film thickness is increased, making it highly resistant to plating solutions.
By doing so, it is possible to stably manufacture a printed wiring board having through holes with high density and excellent insulation between conductor circuits.

Epoxy resin is used as the grease-resistant layer and plating liquid-resistant solder resist used in the present invention.

Funinoxy resin, imiguzole curing agent such as epoxy resin curing agent, aromatic amine curing agent and filler,
Grease-resistant assembly made of thixotropic agent, mosquito material or epoxy resin, phenoxy resin, imidazole curing agent as curing agent for epoxy resin, aromatic amine curing agent and filler, species modifier, organic solvent, triazole, benzotriazole ,
A resin composition comprising one type of compound selected from azimidotoluene and mercaptobenzothiazole is preferred. The grease-resistant layer and the liquid-resistant sulter resist may be the same set.

As the sensitizing agent used in the present invention, for example, a solution of stannous chloride in hydrochloric acid is suitable.

As the activator used in the present invention, a hydrochloric acid acidic solution of radium chloride is suitable.Furthermore, in the present invention, it is also possible to use Catalyst 9F from Silaplay, which uses a sensitizer and an activator χ-liquid. can.

The chemical copper plating solution used in this invention is a plating solution consisting of a divalent copper salt, a complexing agent for divalent steel ions, a complexing agent for -valent steel ions, a surfactant, and a reducing agent for divalent ions. suitable.

Drawings next? A specific example of the method for manufacturing a through-hole printed distribution board according to the present invention will be described.

Double-sided steel foil (
As shown in Figure (b), an alkali-soluble etching self-resist 3 is printed on the insulating plate (35 μm) 2 bonded to the desired conductive circuit pattern using the wafer printing method. Etch the area other than the circuit planned area using a chlorinated steel solution (Figure (C)).Then, hydrate the board at 5%).Immerse it in an IJium solution and perform etching.
After the resist 3 is dissolved and removed (Figure (d)), through-holes 4 for double-sided conduction are drilled at predetermined positions using a press or drill (Figure (e)). Thereafter, soldering of the board is carried out on the entire surface of the board by a solder-registrar screen printing method which is excellent in resistance to plating liquid, leaving the predetermined parts unsoldered, and the solder is heated and cured at 150 DEG C. under SO sorting curing conditions. The liquid solder composition for plating used in this example is as follows.

Egoxy resin (Epicote 152)・・・・・・・・・
...100 parts by weight phenoxy resin PKHH)
・・・・・・・・・・・・ 20〃Talc MS・・
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・1
1. Silicon oxide powder (Aerosil 380)...
・・・－・・・・・・・・・・−・ 4,7〃Phthalocyaning one ・・・・・・・・・・・・・・・・・・・・・
・・・・・・ 5.2# silicone oil (,8H551
10)・・・・・・・・・ 1.2# Robe Chil Cellosolve 1161109.1.1191.1011610
．． 60. .

2-ethyl-4-methylimidazole ・・・・・
・・・・・・・・・ 8 Aromatic amine (ADEKA Hardener EH1013)...20# plating resistant solder・
After forming a resist (resist), use Silapray's 7# chelate (degreasing), a commercially available pretreatment agent for chemical steel plating, water washing, conditioner i 160, water washing, and acid. Washing (2N-Hcl), Kamerist. Water washing, accelerator washing, and water washing were performed to form a plating catalyst (not shown) on the entire surface of the substrate. Next, after drying with a G trowel at 80°C for 10 minutes, the above-mentioned plating liquid-resistant solder resist was printed using the screen printing method, leaving the rough soldering areas (land areas). Cover the surface (other than the planned areas for soldering) with the plating catalyst and apply curing conditions 1.
It was cured at 50°C for 150 minutes (Figure (g)). Thereafter, it was immersed in a chemical steel plating solution for 15 hours, and a copper film 7 of about 50 μm was deposited on the planned soldering area and on the inner wall of the hole as shown in the figure. In the chemical steel plating process, solder joints in which steel deposits and plating catalysts are exposed are selectively formed only in planned areas (lands) and on the inner walls of through-holes. The chemical steel plating solution composition and conditions used in this example are shown below.
It's tori.

Cu So, e 5H20==j 2 g/IED
TA-2Na = d2g/INaO
H = 1t s g/i polyethylene glycol stearylamine = 11]
Omg/' 1 α, α'-dipyridyl = 50mg//
HCHO (57%) = 3mi/i
Plating temperature = 7 (1”c, I)H = 12.2
, speed = 2 + 4 Cu5O, which is a component on the chemical steel solution,
HCHO and pH were kept at constant concentrations using an automatic control device.

In the present invention, since a through-hole printed wiring board is manufactured by the above method, the following effects are achieved.

(1) In this method, a plating-resistant solder resist is formed under the parts where chemical steel plating is not required, that is, except for the planned areas and the hole inner walls, so chemical steel plating is applied to the hole inner walls and lands. It is formed only in Therefore, chemical steel plating has less loss and is economical.

(2) In this method, since a copper foil having a uniform thickness is used for the conductor circuit, it has excellent etching properties and is advantageous for thinning the conductor circuit. Also, since only chemical steel plating is used to form the through holes, advantageous and high density substrates can be produced even with small hole diameters.

(3) In this method, the insulation resistance between the conductor circuits is reduced because the activator T, that is, palladium, which is one of the factors for reducing the insulation resistance, is fixed to the plating-resistant solder/resist layer and is isolated from the conductor circuit layer. High insulation is possible.

(4) In this method, plating liquid-resistant solder
Since the resist forms a double layer, there are no pinholes, and the film is thick, so even if it is immersed in high-temperature, highly alkaline chemical steel plating solution for a long time, it will not discolor the conductor due to penetration of the plating solution and will not adhere to the conductor. There are no defects.

(5) In this method, the process can be simplified because the plating-resistant resist has the characteristics of a solder resist.

As explained above, according to the method of manufacturing a through-hole printed wiring board of the present invention, 5 to 4 conductor lines (0.071w to 0.10 μm) are grown at 2.541 pitches.
It is possible to manufacture a printed wiring board with high channel density, and the insulation resistance between the conductors can be set to 108Ω or more, and it is possible to produce a high-density board at a low cost.

[Brief explanation of drawings]

The figure is a T cross-sectional view showing the steps of the method for manufacturing a through-hole printed wiring board according to the present invention. 1... Glass cloth epoxy grease-resistant laminate, 2... Steel foil, 3... Etching resist, 4... Through-hole, 5.6... Plating-resistant solder resist, 7... Chemical Copper coating. 1 Representative Patent Attorney Usui 1) Toshiyuki

Claims (1)

[Claims] Using an insulating board with a conductor circuit formed in advance, after drilling holes in the predetermined locations on the board, the soldering process involves forming a resin layer, leaving the planned areas, and pre-treating the entire board with chemical steel plating. The process of applying and further soldering leave the planned part,
It is characterized by the process of forming a plating liquid-resistant solder resist, and the process of forming a chemical steel plating on the exposed inner wall of the hole where a chemical steel plating pretreatment agent is formed and on the conductor in the area where soldering is planned. A method for manufacturing a printed wiring board.