JPS6339119B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a wiring board, and particularly to a method of manufacturing a wiring board having through holes.

Today, wiring boards often have through holes from the viewpoint of high-density mounting of electronic components, and accordingly, there is a demand for improved reliability in the conduction state of the through holes. CC for reliability
Although the manufacturing method called the -4 method is excellent, it is not preferable in terms of mass productivity. Therefore, many wiring boards having through holes are manufactured by a method generally called an etched oil method or an additive method.

In the etched oil method, first, holes for through holes are bored at desired positions in a double-sided copper-clad laminate. Next, the side surfaces of the drilled holes are subjected to surface activation treatment, and electroless copper plating is performed. Next, plating copper is deposited and grown on the copper-plated surface and the side surfaces of the holes that have been electrolessly plated by electroplating. Then, the wiring portions on the plated copper on the copper-plated surface are masked with a resist film, and finally the unmasked portions are removed with an etching solution to obtain a desired wiring board having through holes.

The additive method involves drilling holes for through holes in a plastic substrate, applying electroless plating to the entire surface of the substrate including the sides of the holes, then forming a plating resist film in the desired pattern, and finally removing the plating resist. A desired wiring board having through holes is obtained.

However, since all of the copper foil required for wiring in boards manufactured by this method is obtained by plating, it is not possible to expect sufficient chemical and physical adsorption power at the interface between the copper foil and the board. do not have. As a result, so-called pattern peeling occurs over time, making it impossible to produce high-quality wiring boards. On the other hand, the manufacturing method called the etched oil method uses double-sided copper-clad laminates, so pattern peeling does not occur, but since the wiring pattern has a two-layer structure, the amount of copper used is large, the etching time is long, and the line width is It has the disadvantage that fine, high-density patterning is not possible.

Therefore, the present applicant previously proposed in Japanese Patent Application No. 56-116566, while retaining the advantages of double-sided copper-clad laminates,
A method of manufacturing a wiring board as shown in FIG. 1 was proposed, which eliminates the above-mentioned drawbacks. The manufacturing method shown in FIG. 1 is as follows. As the starting substrate, a copper-clad laminate is used, as shown in FIG. 1A, in which copper foil 2 of about 35 μm is adhered on both sides of a substrate 1 made of epoxy or phenol material. By masking the wiring portion with a resist film 6 and etching the unmasked portion in the step shown in FIG. 2B, the wiring pattern shown in FIG. 2C is obtained. Next, holes 3 for through-holes are drilled at predetermined locations, resulting in a structure as shown in figure D. Then, the surface of the substrate excluding the through holes 3 is masked with a conductive ink 7, which is an example of a conductive thin film, and an acid-resistant or alkali-resistant ink 8, which is an example of an acid-resistant or alkali-resistant thin film, as shown in FIG. . After masking with ink, activation treatment with palladium or the like, electroless plating is performed to form a thin film-like conductive layer 4 on the side surface of the through hole 3 as shown in FIG. Note that the electroless plating step may be performed before or immediately after printing the conductive ink. Furthermore, a conductive film may be used instead of the conductive ink. Conductive ink 7 in the process of G in the same figure.
Electroplating is performed using the electrode as one electrode to deposit approximately 35 μm of plated copper on the conductive thin film 4. Finally, conductive ink 7 and acid-resistant or alkali-resistant ink 8 are laminated in the process shown in FIG.
By removing , a wiring board having through-holes as shown in FIG. 2H can be obtained.

However, although the manufacturing method described above overcomes the drawbacks of the conventional manufacturing method, the masking accuracy in the step of FIG. 1E is generally not very good. This is because masking with the conductive ink 7 and the acid-resistant and alkali-resistant ink 8 is usually performed by means such as printing, so it is extremely difficult to set the accuracy to about 1 mm or less. The reason why the conductive ink 7 is masked on the entire surface of the substrate except for the through holes 3 in FIG. be. Therefore, among through holes that are relatively very small compared to the overall size of the board, through holes with ring-shaped patterns that are not connected to other parts on the front and back sides are masked with conductive ink. However, it is extremely difficult to cover a ring-shaped copper foil pattern with a width of only 1 to 2 mm at most, and if the masking is insufficient, the side of the through hole 3 is covered with plated copper. If the deposition ceases or if the masking is excessive and the conductive ink 7 covers the through hole 3, there is a problem that electroplating cannot be performed on the side surface of the through hole 3. Further, even if the through hole 3 is not blocked by the conductive ink 7, the conductive ink 7 will only slightly enter the inside of the through hole 3, and the electroplating on the side surface of the through hole 3 will be incomplete. There was a drawback.

In view of the above-mentioned circumstances, the purpose of this invention is to enable highly accurate patterning without pattern peeling, short etching time, and to reduce the precision of the masking process with a conductive thin film, thereby increasing production efficiency. An object of the present invention is to provide a method for manufacturing a wiring board having improved through holes.

To summarize, this invention is a process of selectively etching a double-sided copper-clad laminate to form a desired wiring pattern, in which a through-hole is formed around a through-hole that is to be an independent through-hole that is not connected to other parts. It is characterized by forming a ring-shaped copper foil pattern having terminal-like protrusions.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows the main parts of the wiring board manufacturing method according to the present invention in the order of steps. Note that the same or equivalent parts in the configuration as in FIG. 1 are given the same reference numerals.

The process shown in FIG. 2A corresponds to the processes shown in FIGS. 1A and 1B. On the copper foil 2 of a 35 μm double-sided copper-clad laminate with an epoxy material or phenol material as a substrate, wiring parts including through holes to be made into through holes are screen printed with epoxy ink, and a plating resist film 6a, Get 6b. In this case, the plating resist film 6b, which includes a through-hole section that should be an independent through-hole that is not connected to other parts, has a resist pattern in which a terminal-like protrusion 6c is provided at one location around the circle. The process in Figure 2B is shown in Figures 1C and D.
This corresponds to the process of resist film 6a,
After applying 6b, the non-masked portions are removed using an etching solution to expose the base material 1 made of epoxy or phenolic material. Then, copper foil patterns 2a, 2b having the same shape as the resist films 6a, 6b are formed in the portions where the resist film is applied. The copper foil pattern 2b, which includes a through-hole portion which should be an independent through-hole that is not connected to other parts, has a terminal-like protrusion 2c at one location around the circle. Copper foil pattern 2a, 2
After forming b, a through hole 3 is bored in a portion to be a through hole. At this stage, the independent copper foil pattern 2b that is not connected to other parts becomes ring-shaped. The process shown in FIG. 2C corresponds to the process shown in FIG. 1E. When the formation of the substrate surface by forming the through holes 3 in the copper foil patterns 2a and 2b is almost completed, processing of the side surfaces of the through holes 3 is started. The side surfaces of the through holes 3 are electroplated, and conductive ink 7 is printed between the copper foil patterns 2a and 2b by screen printing in order to make both sides of the board conductive. This is because the copper foil patterns 2a and 2b act as one electrode during electroplating, so it is necessary to maintain continuity between the copper foil patterns. The conductive ink 7 is printed on the entire surface of the substrate except for the through holes 3, but if the conductive ink 7 enters the through holes 3, electroplating will not be completed completely, so the ring-shaped copper foil pattern 2a, 2b is avoided as a whole. However, the ring-shaped copper foil pattern 2b that includes the through hole 3, which should be an independent through hole that is not connected to other parts, comes into contact with the conductive ink 7 through the terminal-like protrusion 2c. For this reason, even if the accuracy of the printing process is greatly relaxed, which involves masking the entire board with conductive ink 7 while avoiding the through holes 3 as shown in Figure 2C, it will not affect the next electroplating process. None. Therefore, the process of masking with this conductive ink 7 can be greatly speeded up.

After masking with the conductive ink 7, a process similar to the method previously proposed by the applicant is performed. The entire surface of the base material 1 excluding the tip 3, that is, the top of the conductive ink 7 and the base material 1 where the conductive ink 7 is not masked
Acid-resistant or alkali-resistant ink is masked on the top and on the copper foil patterns 2a and 2b. Then, electroless plating is performed on the side surface of the through hole 3 to form a conductive thin film, and electroplating is performed using the copper foil patterns 2a and 2b, which are electrically connected by the conductive ink 7, as one electrode, to form a conductive thin film. Approximately 35 μm of plated copper is deposited on top. Finally, by removing the laminated conductive ink 7 and acid-resistant or alkali-resistant ink, a wiring board having through holes is obtained.

As described above, according to the wiring board manufacturing method of the present invention, a ring-shaped copper foil pattern having terminal-like protrusions is formed around the through-hole that should be an independent through-hole that is not connected to other parts. The precision of the process of masking with the conductive ink 7 is greatly reduced, and all through holes can be reliably electroplated. Therefore,
The process of masking with the conductive ink 7 can be speeded up, which has the advantage of improving production efficiency as a whole.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing in order of steps a method for manufacturing a wiring board having through holes, which is the premise of the present invention, and FIG. be. 1...Base material, 2...Copper foil, 2a, 2b...Ring-shaped copper foil pattern, 2c, 6c...Terminal-like protrusion, 3...Through hole, 4...Copper foil film, 5...Plating Copper, 6... Resist film, 7... Conductive ink, 8
...Acid-resistant or alkali-resistant ink.

Claims (1)

[Claims] 1 (a) A double-sided copper-clad laminate is selectively etched to form a desired wiring pattern. (b) Drill holes for through holes at designated locations. (c) Masking the surface of the substrate except for the through holes with a conductive thin film that can be cleaned or peeled off, and an acid-resistant or alkali-resistant thin film that can be washed or peeled off. (d) Forming a conductive layer in the through hole portion by electroless plating. (e) Using the conductive thin film as one electrode, a metal foil of an appropriate thickness is formed on the conductive layer by electroplating. (f) removing the conductive thin film and the acid-resistant or alkali-resistant thin film; In the wiring board manufacturing method having the above steps (a) to (f), in the step (a), a terminal-like protrusion is provided around the through hole that should be an independent through hole that is not connected to other parts. A method for manufacturing a wiring board having through holes, the method comprising forming a ring-shaped copper foil pattern.