JPH0231871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a double-sided printed wiring board for mounting semiconductors, and particularly to an improvement in the method for manufacturing a printed wiring board having wire bondability.

[Prior art]

There are two methods of manufacturing printed wiring boards: the subtractive method and the additive method.
There is also a manufacturing method that combines the above-mentioned subtractive method and additive method, such as the invention described in Japanese Patent No. 194598. However, these methods
This method examines how to form a conductor circuit on an insulating base material, and does not consider the manufacturing process up to the point of applying gold plating, etc., to the formed conductor circuit.

A method for manufacturing printed wiring boards that also considers the manufacturing process up to the point of applying gold plating etc. on the conductor circuits to be formed, that is, a double-sided printed wiring board for mounting semiconductors with wire bonding properties (generally wire bonded parts (bonding parts)). Two types of methods are generally used in the manufacturing method of (d) a printed wiring board with nickel plating and soft gold plating.

The first method is to form a circuit pattern on a conductor layer on an insulating base material by a tenting method using a positive pattern of a photosensitive film together with a lead wire for gold plating, and then mask it with a photosensitive solder resist film or solder resist ink. This is a method of selectively plating nickel and gold only on the necessary areas.

In this method, nickel and gold plating is applied not only to the surface but also to the edges of the required circuit pattern, so that the dimensions that allow wire bonding on the bonding pad correspond to the apparent dimensions. In other words, it can be said that this is a method of manufacturing a printed wiring board with a good yield in the wire bonding process when semiconductors are mounted. Furthermore, since gold plating is applied only to the necessary parts, there is also the advantage that printed wiring boards can be manufactured at relatively low cost.

The second method is to apply nickel and gold plating to the conductor layer on the insulating base material through a negative pattern of photosensitive film or printing ink by photography or printing, and then use the plating as a resist to etch the circuit pattern. This is the so-called gold resist method.

In this method, since the conductor layer on the entire surface of the insulating base material is used as a lead wire for gold plating, there is no need to intentionally attach a lead wire for gold plating, and wiring design is easy.

[Problem to be solved]

In the technique described as the first method, since gold plating is applied after forming a circuit pattern, lead wires for gold plating are required for all circuit patterns. If an isolated pattern without a lead wire for gold plating exists, not only will that part not be plated with gold, but the exposed copper of the pattern will dissolve into the gold plating solution, causing defective plating. Therefore, it is necessary to design wiring to provide lead wires for gold plating in all circuit patterns, and this work requires skill and time, making it difficult to follow the recent trend toward high-density wiring. .

In the technique described as the second method, the surface cannot be sufficiently cleaned after gold plating due to the plating resist film formed by photography or printing, and the highly corrosive plating solution remains on the substrate surface as a residue. I get tired. Furthermore, a phenomenon called overhang occurs due to etching, and the apparent dimensions of the bonding pad become smaller than the actual dimensions, resulting in defective bonding. Furthermore, corrosion of the copper exposed on the side surfaces of the pattern occurs. Furthermore, it is necessary to apply gold plating to the entire surface of the circuit pattern, which increases the cost of gold compared to the technique described as the first method.

[Means for solving problems]

The present invention takes advantage of the respective advantages by appropriately combining the first method and the second method, and provides gold plating with the necessary wire bonding properties for the bonding terminal portion, while also eliminating the need for complicated The present invention provides a manufacturing method that does not require wiring design and allows a printed wiring board for mounting a semiconductor to be easily obtained.

That is, the present invention is a method for manufacturing a double-sided printed wiring board for mounting a semiconductor, which includes the following steps in order.

(1) The process of drilling holes at desired positions on the insulating base material.

(2) Process of plating through holes.

(3) A process of etching one side for semiconductor mounting through a photosensitive film to form a desired pattern.

(4) A step of forming a plating resist made of a photosensitive film on the other side.

(5) Plating power is supplied to at least one pattern on the one surface for semiconductor mounting from the other surface through the through hole, and the one surface for semiconductor mounting and the other surface are plated with nickel and gold. The process of applying.

(6) A step of removing the plating resist.

(7) A step of etching the other surface through the nickel and gold plating to form a desired pattern.

[Action and effect]

The present invention provides a configuration in which power is supplied from the other surface to at least one pattern on one surface for mounting a semiconductor by plating through a through hole, and the one surface for mounting the semiconductor and the other surface are plated with nickel and gold. By having this, it is possible to eliminate or reduce the number of lead wires for plating on one side for mounting semiconductors by simply performing the easy process of forming holes for through holes at arbitrary locations on the insulating base material. This eliminates the complexity of wiring design and allows for high-density wiring.

In addition, since the pattern formed on one surface for semiconductor mounting, which requires wire bondability, has a structure in which the entire surface including the end surface is plated with nickel and gold, the bonding pad's apparent dimensions are It is possible to provide a printed wiring board with wiring accuracy matching the dimensions of . Moreover, with this configuration, the conductor circuit will not corrode from the exposed end face of the pattern.

Furthermore, since the surface for semiconductor mounting can be thoroughly cleaned after gold plating, the highly corrosive plating solution does not remain as a residue on the base material surface, providing a printed wiring board with excellent wire bonding properties. can.

That is, the present invention solves many problems that are not solved even in the invention described in JP-A-57-194598, by solving the problems of the invention from the first method and the second method described in the prior art. By creating an appropriate configuration that extracts only the strengths of each component as a whole, it is possible to stably manufacture double-sided printed wiring boards for mounting semiconductors, which require pattern accuracy and wire bonding properties. It has an effect that can be easily achieved.

〔Example〕

FIG. 1 is a longitudinal sectional view of a so-called double-sided copper-clad laminate board in which copper foil is attached to an insulating base material mainly made of glass cloth and organic resin. FIG. 2 is a diagram showing the board with holes drilled at desired positions, and FIG. 3 is a longitudinal sectional view showing the board after the holes are drilled and plated with through-hole copper. Next, photosensitive films are attached to both sides of the substrate, a positive pattern of a desired circuit is printed on the semiconductor mounting surface, and the entire surface of the other side is exposed and then developed. FIG. 4 is a cross-sectional view in this state. In the figure, the a side is the semiconductor mounting surface. Here, the semiconductor mounting portion needs to be limited to the a-plane side. In addition, conductivity for nickel plating and gold plating on the A side in the post-process can be led from the B side through through-hole copper plating.It depends on the pattern arrangement, hole position, and number of holes, but in particular, the plating lead wire can be connected. It is not necessary to provide it, and there is no problem even if it is provided. This step is one of the most significant features of the present invention, and allows wiring design to be simplified. In addition, the photosensitive film that is exposed on the entire surface of the b-side is intended to protect the copper plating in the through holes and the copper on the b-side surface from etching. It is not limited to photosensitive film as long as it can withstand the liquid. Next, after etching,
Perform peeling of the photosensitive film. FIG. 5 is a cross-sectional view in this state. Thereafter, a photosensitive film is attached only to the b side to form a negative pattern. In this state, a copper pattern is formed on the a side, and a negative pattern made of a photosensitive film is formed on the copper foil on the b side. If a solder resist is required on the A-side, the A-side may be coated with the solder resist before bonding the photosensitive film to the B-side. Next, both sides are nickel-plated and gold-plated, and since the a-side side is nickel-plated and gold-plated to the edge of the pattern, the desired line width accuracy can be obtained, and the longitudinal cross-sectional view in this state is shown in Figure 6. be. After that, after removing the photosensitive film on the B-side, etching is carried out to form a pattern on the B-side, but the edges of the pattern on the A-side are completely etched with solder resist, nickel plating, and gold plating. Since all parts are protected, the pattern on the a-plane side will not be etched. The longitudinal cross-sectional view in this state is the seventh
It is a diagram.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of a double-sided copper-clad laminate board, Figure 2 is a vertical cross-sectional view of the board with holes drilled in it, and Figure 3 is a vertical cross-sectional view of the board with through-hole copper plating after the holes have been drilled. FIG. 4 is a longitudinal cross-sectional view when a photosensitive film is printed on the substrate after through-hole copper plating and then developed. In the figure, the a side shows the semiconductor mounting surface, on which a positive pattern of the photosensitive film is printed, and the b side shows the entire surface of the photosensitive film exposed. FIG. 5 is a vertical cross-sectional view of the substrate after etching, and FIG. 6 is a vertical cross-sectional view of the substrate after forming a negative pattern of a photosensitive film on the b side and then nickel plating and gold plating. FIG. 7 is a longitudinal cross-sectional view of the case where it is etched after being nickel-plated and gold-plated. 1... Insulating base material, 2... Copper foil, 3... Through-hole copper plating, 4... Etching resist, 5...
...nickel plating, gold plating, 6...metal plating resist, 7...nickel plating, isolated pattern without lead wire for gold plating.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a double-sided printed wiring board for mounting a semiconductor, the method comprising the following steps in order: (1) The process of drilling holes at desired positions on the insulating base material. (2) Process of plating through holes. (3) A process of etching one side for semiconductor mounting through a photosensitive film to form a desired pattern. (4) A step of forming a plating resist made of a photosensitive film on the other side. (5) Plating power is supplied to at least one pattern on the one surface for semiconductor mounting from the other surface through the through hole, and the one surface for semiconductor mounting and the other surface are plated with nickel and gold. The process of applying. (6) A step of removing the plating resist. (7) A step of etching the other surface through the nickel and gold plating to form a desired pattern.