JPS5966192A - Method of producing both-side 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 an llj-plane printed wiring board.

Conventionally, the commonly used method generally takes the following steps.
■Circuit is formed by printing on both sides of an insulating substrate.
(Through drilling or punching l is used to form a through hole. ■Fill the through hole with conductive paint and connect the front and back circuits. There are three main ways to fill this conductive paint: .

■ For example, as disclosed in Patent Publication No. 1501, a pin coated with magnetically conductive paint (silver paste, etc.) is inserted into a through hole and moved up and down to pass through the conductive paint. How to fill the hole. that time,
Bringing conductive paint into contact with the Omotesakura circuit is also not a way to tell fortunes.

@ A method of filling through holes with #electric paint using silk screen printing.

As shown in the specification and drawings of θ Special @ Sho J7-7117, a method of pushing conductive paint up toward the through-holes from below the substrate to fill the through-holes.

Each of these @ and θ methods has the following problems.

Method ■... ■The amount of conductive paint attached to the tip of the bottle tends to fluctuate, resulting in insufficient filling and connection failures. ■Extremely high pin accuracy is required. If even one of the many pins is bent, it will not be possible to insert it into the through hole.

@ method...The position of the silk screen's minute mesh and the through hole are often misaligned. The amount of 21# magnetic paint held on the mesh varies. In other words, the paint may not be filled sufficiently, which can easily cause a connection failure.

θ method: A fixed plate with holes shaped to match the through-hole pattern and a sensor pink holding plate filled with 4 types of paint (all called masks) are used to use the through-hole pattern. In addition, it is necessary to prepare a dandelion, and equipment costs including other incidental equipment will increase. In addition, productivity is low as it takes time to replace the fixed plate and presser plate.

This fit-fJ person believes that the root cause of the problems with the conventional methods described above is the procedure of forming through holes on a board on which circuits have already been formed and filling them with conductive paint. I think there is.

In other words, all of the three conventional methods described above require very fine filling work.

This is because the conductive paint must be applied to the circuits on the front and back sides of the board at some of the circuit parts around the edges of the through holes. The circuit pattern is extremely dense and the gaps between adjacent parts are minute, so if even a small amount of conductive paint protrudes, incorrect circuit connections will occur.

On the other hand, contradictory factors such as the fact that the adhesion area for each circuit on the front and back is limited to a narrow range, while the through-holes must be filled with a sufficient amount of conductive paint are also contributing factors. one of.

Based on such considerations, the present invention has been developed by forming through holes in a substrate before forming a circuit, filling the through holes with conductive paint, and then forming a circuit, thereby achieving the above-mentioned This is an attempt to solve the problems seen in the past.

The gist of the method for manufacturing a double-sided printed wiring board of the present invention is that it consists of the following steps (a) to e).
The outline is shown in (a) to (e) of Figure 1.

(a) Insulating board with no circuit formed (through hole in 11)
2) The first step of forming. There are two types of this insulating substrate fl) on which no circuit is formed:

(1) Double-sided copper-clad laminate. (II) A bare board with no copper cladding on both sides.

(b) A second step of filling the through hole (2) with a conductive paint (3).

(c) Surplus conductive paint (
3) The third step of removing.

2) In the second step, the insulating substrate (
1) Pad 14) with conductive paint on top.

15) Fourth step of forming.

(E) Front and back pads formed in the fourth step +41,
A fifth step of forming circuits +61 and (71) on both the front and back sides of the insulating substrate +11 in a state of covering and bonding to each of +51.

When a double-sided copper-clad laminate is used in the first step (a), the formation of the circuits +61, +7) is carried out through the steps of masking ink printing, etching, and masking ink removal. When using a bare board without copper cladding on both sides, use this circuit (6).

(7) is formed by stamping and drying the conductive paint □ Before forming the circuit on the insulating substrate il+, the present invention committee makes a through hole (2) and applies the conductive paint (3) to it.
Since the conductive paint (3) is filled in a sufficiently large amount to the through hole (2), there is no strict constraint as in the conventional method, such as that the conductive paint (3) must not be exposed to the circuit or protrude at the bottom, and it can be squeezed Relatively rough methods such as injection using a tube can be used, and filling can be done very easily.

Moreover, the reason why such a large amount of conductive paint (3) can be filled is that the excess conductive paint 13 cut on the substrate (II) is removed in the third step (c).

It is easy and preferable to remove it by polishing the front and back surfaces of the substrate (1) after the conductive paint (3) filled in the through hole (2) has semi-cured or hardened. Such polishing is possible because no circuit has been formed on the substrate +11 yet. In other words, there is no need to worry about damaging the circuit by polishing. - There are very few cases where conductive paint is
During the removal of step 3), a portion of the front surface and 1 m of the back surface may be removed, resulting in a dent as a whole. Therefore, if the circuit ill, +71 is to be formed immediately after the third step, the conductive paint inside the through hole (3) and the circuit (6).

(7) Electrical connections are likely to be defective.

However, in the present invention, (in the fourth step of the process), a pad +41 of conductive paint is placed on the substrate fil, aiming at both the front and back sides of the conductive paint (3) inside the through hole.
, F51G is formed. This pad (4).

(5) is formed on the front and back surfaces of the substrate (the board) in a state in which it is securely bonded to both the front and back surfaces of the through-hole conductive paint +31.

After that, in the fifth step of glueing J→, the circuits +61 and +71 formed on both the front and back sides of the substrate fl are pads +4
1 and +51, so that the conductive paint inside the through hole (3), the back side pad (6), and the back side circuit (7) are in contact with each other over a sufficiently wide area. This ensures a reliable electrical connection.

From the above, it can be said that h according to the present invention has the following effects.

b) The state of electrical connection between the front surface circuit and the back surface circuit of the board via the conductive paint in the through-holes can be made much better than in the conventional method.

(b) Filling the through holes with conductive paint, which is the most important point and the root cause of problems in the past, can be done easily and in sufficient quantities. Although the fourth band forming step increases the number of steps, this is a simple step and can lead to improved productivity overall.

(c) The means for filling conductive paint into the through-holes is as follows:
As shown in the example above, it can be done simply by squeezing or injecting through a tube, which is advantageous in terms of capital investment.

Next, the present invention will be explained in detail.

Figure 2 (A) or (C) shows the second process (Figure 1 (B)).
(see) details. In other words, the conductive paint (31) placed on the surface of the insulating substrate +11 is squeezed using a scraper (8), and then filled into the through holes (2) with a cap that completely fills the conductive paint (31). (
The conductive paint (3) protrudes from the back side of the plate, but this is squeezed out with a scraper (9).

Such squeezing leaves an extremely thin film of conductive paint 13'l, +3' on the front and back surfaces of the substrate ().
Only 1 left. It is removed by polishing.

The formation of pads +41 and +51 in the fourth step is performed by a screen marking method, a spray method, or a stamp method.
dry.

The formation of the circuits +61 and +71 in the fifth step is carried out in the first step by stamping and drying a conductive paint on a substrate with bare surfaces on both sides (if 1+ is used). The process is shown in FIG.

Further, when a double-sided copper-clad laminate is used in the first step, the steps of printing masking ink, etching, and removing masking ink are performed.

The situation is shown in FIGS. 4 and 5.

101, 1ll) is copper clad, tta, (l is masking ink, tel, 171 is a circuit formed by etching and removal of masking ink α21.Q31.

After the circuits +61 and +71 are formed, solder resist is printed and electronic device symbols are printed, which is the same as in the conventional method.

Note that the through hole +21 in the first step may be formed by a drilling method or a punching method, and the punching method is preferable because it requires less man-hours. In the case of punching, the shape of the through hole (2) is, for example, a concave, concave shape as shown in Fig. 3.

According to the filling method of the present invention, even a through hole (2) having such a cross-sectional shape can be filled with a sufficiently large amount of conductive paint 13).

Although it is possible to apply the method to the single-plate production method, it is more preferable to apply it to the multi-plate production method. That's the 6th
As shown in the figure. In other words, a group of through holes (2) in a predetermined pattern with respect to the compound base ff1 (l) shown by the imaginary line are drilled in the large insulating blank plate 04J, and from then on, the large insulating blank plate 04J is drilled. Then, the second to fifth steps of the method of the present invention are carried out. After that, the double-sided circuit-formed veneer (1 to 1) is cut out from the dog-shaped raw board circle as shown in Fig. 7 to produce a product. be.

[Brief explanation of the drawing]

(A) to (E) in FIG. 1 are schematic sectional views illustrating the steps related to the gist of the present invention, and A) to C) in FIG. Figure 3 is a schematic cross-sectional view of the intermediate and completed assembly when using bare insulating plates on both sides, and Figure 6 is a schematic cross-sectional view of the insulation when using the multi-plate manufacturing method. FIG. 7 is a plan view showing a completed printed wiring board manufactured by this method. 14 (1) ...Insulating substrate, (2) ...Through hole, H31, i3'l ... Conductive paint, +
4) , +5) ... pad, [61, (71...
circuit.

Claims (1)

[Claims] ■ A method for manufacturing a double-sided printed wiring board comprising the following steps: (a) Through-holes (
2) The first step of forming. (b) Apply conductive paint (3) to the through hole (2) above.
The second step is filling. (c) Surplus conductive paint remaining on the insulating substrate (1) (
3) The third step of removing. ) The conductive paint filled in the through hole (2) in the second step (pad 141, i5) made of conductive paint is placed on the insulating substrate (1) while being bonded to both the front and back surfaces of the pad 31.
The fourth step is to form. (e) Both front and back bands 141 formed in 9IS4 process,
A fifth step of forming circuits +61 and +71 on both the front and back surfaces of the insulating substrate +1) in a state where they are coated and bonded to each of the circuits +151. (2) The double-sided method according to claim 0, wherein the conductive paint 131 is filled into the through hole (2) in the second step by squeezing the conductive paint (3) placed on the insulating substrate fil. A method for manufacturing printed wiring boards. ■ The excess conductive paint (3') removed in the third step is replaced with conductive paint (3') filled into the through hole +21.
Holding by polishing after semi-curing or curing of 1.
F. A method for manufacturing a double-sided printed wiring board according to claim 0. ■ Insulating substrate with no circuit formed in the first step +1
), a double-sided copper-clad laminate is used, and the formation of the circuits 161 and 171 in the fifth step includes the steps of stamping masking ink, etching, and removing masking ink. A method for manufacturing printed wiring boards. ■ Insulating substrate il with no circuit formed in the first step
Use a material that is not steel-clad on both sides as l, and
1ii6. The method of manufacturing a printed wiring board according to claim 0, wherein the formation of the circuits (6) and (7) in the fifth step is performed by printing and drying a conductive material.