JPS5844798A - 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 method for manufacturing a printed wiring board (hereinafter referred to as a wiring board), and in particular, to selectively form a catalytic metal layer on the inner wall surface of a through hole by a photochemical reaction, and further by electroless plating. , relates to a method of manufacturing a wiring board on which a conductor layer is formed.

In recent years, with the increasing integration of electronic devices such as ICs and L8Is, wiring boards have become more compact with the aim of improving packaging density.
Trends such as thinning of circuit patterns, small hole diameter ratio of through holes, and increase in plate thickness due to increase in volume are becoming higher. For this reason, in manufacturing wiring boards, it is necessary to achieve high precision from the viewpoint of high electrical roughness. on the other hand,
When considering mii characteristics, it is also important to maintain a high yield during manufacturing. As a countermeasure to these problems, various attempts have been made to make each circuit pattern thinner and more precise, using both the etched foil method and the additive method.

In the former etched foil method, the copper foil is 1rM.
Attempts have been made to improve thinning (hereinafter referred to as J'l'e foil), uniformity of electroplating thickness, and photoprinting of L5 system printing equipment.

However, the uniformity of film thickness in electroplating is particularly difficult, and this hinders the development of finer lines and higher precision in circuit patterns. On the other hand, in the latter 7-day tape method, it is difficult to ensure strong contact between the circuit pattern and the laminate because the circuit pattern is a thin line. Furthermore, in the case of a multilayer board that includes a conductor layer in the inner layer, in order to strengthen the contact*1 between the 5-circuit pattern and the laminate, the inside of the laminate is usually roughened and etched with a mixture of chromic acid and sulfuric acid. At this time, the conductor exposed on the inner wall of the hole is etched at the same time, which adversely affects the reliability of the inner layer conductor, which is not preferable.

In addition, the electroless steel plating layer that forms one circuit pattern is curved, which reduces tensile strength compared to the electrolytic steel plating layer, and the laminate has a large wire tension wheel, so it is formed with electroless steel plating. A small circuit pattern has no resistance to this. In applications where thermal factors are present, the high degree of obscurity may cause disconnection of the circuit pattern, which is unfavorable in terms of reliability. When the through-hole diameter of the board is small and the board thickness is thick, that is, when the hole diameter to board thickness ratio (aspect ratio) becomes large, it is extremely difficult to apply plating uniformly to the inner wall of the through-hole using electroplating. It is a national disaster and 1 document, Copper Plating Adpanst Y Rudelayer Board Copper Pl
Ating Advanced Multilayer
Hoards'(Il'U*1976 Fall M
When the aspect ratio is l:6, the plating coverage is 90%, and when the aspect ratio is 1:lO, the plating coverage is 70%, which is insufficient for high-density wiring boards. It is. On the other hand, in the Atitip method, the coverage of the plating is sufficient and becomes 100% even if the aspect ratio becomes large, according to the above-mentioned literature. However, as mentioned above, for multilayer boards containing conductor paths in the inner layers, a problem arises in the reliability of the inner layer connections, and this method cannot be said to be sufficient for manufacturing high-density wiring boards. For this purpose, a copper-clad laminate with an inner layer conductor pattern t-V is formed, a circuit pattern is formed on the surface of the plate by etching in advance, a hole is bored, a catalyst liquid is applied to the inner wall of the hole, and a catalyst liquid is applied selectively to the inner wall of the hole. irradiate with ultraviolet rays,
We proposed a method for manufacturing a wiring board having a highly precise pattern in which fine lines are formed by forming a catalytic metal layer and a conductor layer by electroless plating. However, in this method, the catalytic metal is precipitated by a photoreduction reaction only on the pore walls that have been irradiated with the phagocytosis, so it is difficult to uniformly irradiate ultraviolet rays on the pores that fit into the irregularities or on the pore walls with a large aspect ratio. There were a few drawbacks.

The purpose of the present invention is to solve all of the drawbacks of the conventional method, and it is an object of the present invention to solve all the drawbacks of the conventional method.
The present invention aims to provide a method for manufacturing a mounting plate that forms a uniform conductor m on the inner wall of a small hole.

According to the present invention, a method for manufacturing a through-hole printed siding board is obtained, which is characterized by comprising the following steps 1 to 1.

(1) Step 1 of forming a pattern on a steel-clad laminate using a dry film or resist ink serving as an etch resist and etching it to form a conductor pattern; (2) Drilling holes at desired positions in the laminate.

(2) A step of immersing the laminated board in a sensitizing solution to form a sensitizing layer on the surface and the hole wall surface; [Phase] (2) A step of irradiating the holes of the laminated board with ultraviolet rays.

[Co., Ltd.] A step of immersing the above plate in an activation liquid to deposit catalyst metal on the inner wall of the hole.

[Co., Ltd.] A step of immersing the laminate in an electroless plating solution to provide a conductor layer on the hole wall surface.

This will be explained based on FIG. 1.

FIG. 1 (5) is a multilayer laminate (hereinafter abbreviated as laminate) lOwTrfI having a conductive pattern on the inner layer, and the surface 601 is integrally molded with a layer of copper foil 2.

Is there a dry film or resist ink applied to this laminate 1? After the etching resist pattern is applied, the copper foil 2 is removed from the desired portions using a known etching method to form a four-body circuit pattern (hereinafter referred to as "circuit turn") 2a in a dragon circle (see Fig. 1). (Yen).

Next, in order to protect the five circuit patterns 2at, a plating-resistant coating material is applied to the surface of the laminate plate 1 to form a permanent protective mask 3 (FIG. 1(B)).

Thereafter, a through hole (hereinafter referred to as hole) 4 is drilled at a desired location in the laminate l using a drill (FIG. 1 QJ)).

Next, 1 reference photoimaging process for print, circuit mani 7 actuator (4'hoto-i)
Creating process for Pr1nte
d C1rcuitjbnufacture(1,B,
A thickening solution of stannous chloride, as known from Goldman+Plating), i.e. 10 g of stannous chloride/
A sensitizing layer 5 made of stannous chloride is formed on the surface of the laminate 1 and the inner wall of the pores 4 by immersing the plate in a solution of L+hydrochloric acid 10 t/lO for about 2 minutes (see Fig. 1 (1)). −)). Next, without exposing only the inner walls of the holes 4 to the surface of the laminate 1, a hole positive film 6 was soaked on the surface of the laminate 1 to make it happy, and then ultraviolet rays were irradiated from both the upper and lower surfaces with a low-pressure mercury lamp (the first
1 son)).

' Through this step, only the sensitizing layer 5 made of tin chloride on the surface is oxidized to form the stannic chloride (8nt'14) layer 5a.
(Figure 1 (Ci)).

Next, the laminate 1 having the second chloride layer 5a formed on its surface is immersed in an activating solution of 1 g/L of palladium chloride + IQmt/L of hydrochloric acid for about 2 minutes, so that palladium t-reduction is precipitated on the inner walls of the holes 4. Furthermore, through the water washing process, the coating -〇Stannic chloride layer 5
a is removed and a catalyst gold layer 7 of rose and dium is formed only in the hole M4.
(Fig. 1).

When this laminate l is immersed in an electroless copper plating solution such as CP-70 manufactured by Poulet, the catalytic metal layer 7 becomes a nucleus and the copper conductor layer 8 forms the hole 4. formed on the inner wall
A conductor (b) path is formed in the laminated plate l (Fig. 1 (1)).

According to the above two aspects of the present invention, only copper of a fixed thickness is etched without plating on the surface (3) of a 1-inch copper-clad laminate. 0.035m is rare, but with a tolerance of *0.0111111, high precision can be achieved.

(ll) Also, even with a circuit pattern having a value set of about Q, 1lIs, stable adhesive strength that can sufficiently withstand thermal factors can be obtained.

(ii) Selective copper-free plating only on the inner wall of the hole
Compared to the full aguitip method, in which electroless copper plating is applied to the circuit pattern, the handle cost of deposited copper is approximately 1
/10, resulting in a significant cost reduction.

OV) In addition, the aspect ratio is large, and even if the hole walls are uneven, there are no defects, and plating with a uniform thickness can be obtained, resulting in stable quality.

(V) Since the circuit pattern is formed by the etched foil method, there is no need for roughening etching similar to the core layer, which can be safely performed using the itip method. Therefore, the non-conductor layer in the multilayer board is not etched and the reliability is 90%.
A printed wiring board of 4 degrees is obtained.

Note that the method for manufacturing a printed wiring board of the present invention can also be adopted in the manufacturing process of a multi-wire wiring board, so it is not particularly effective from the viewpoint of high precision and shredability.

[Brief explanation of drawings]

FIGS. 1(f) to (1) are process diagrams showing the method for manufacturing a printed wiring board of the present invention. l... Copper-clad laminate (with conductor pattern on 1), 2... Steel foil on surface layer, 2a...
...Conductor circuit pattern %3...Protective mask,
4...hole, 5... group/sensitizing layer (tinn chloride layer)
, 5a...Stannic chloride layer. 6...Positive film, 7...Old catalyst metal layer (palladium), 8...(Electroless copper plating)
Conductor layer・Fig. 1 Fig. 2 Fig. 1

Claims (1)

[Claims] A method for producing a printed wiring board characterized by having the following steps: ■ Forming a pattern on a copper-etched laminate using a dry film or resist ink serving as an etching resist, and etching it. A process of forming a conductive butter. (2) A step of forming holes at desired positions in the laminate. (2) A step of soaking the laminate in a sensitizing solution to form a sensitizing layer on the surface and the hole surface; (2) A step of irradiating the outer edge of the laminate except for the holes. Q The above product l-board 1! - A step of depositing catalytic gold K14 on the inner edge of the hole by immersing it in an activation liquid. A step of immersing the laminate in a 1j91 plating solution to form a conductor layer on the hole wall surface.