JPS61136290A - Repair for multilayer printed wiring 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] [Field of Industrial Application] The present invention relates to a method for repairing a multilayer printed wiring board, and in particular to a method for repairing a short-circuit defect between a through-hole conductor layer and an inner layer pattern. 2. Description of the Related Art As devices become more highly integrated, there is a growing demand for higher density printed wiring boards.

For this reason, multilayer printed wiring boards have come into widespread use.

Conventionally, in the general manufacturing method of multilayer printed wiring boards, first,
An inner layer board is manufactured by forming a signal pattern or a power ground pattern as an inner layer pattern on the copper layer of a steel clad laminate by a printing/etching process. Next, the inner layer substrate and the single-sided copper-clad laminate are used as an outer layer substrate and are superimposed on Gripreg and heated and pressed to form an integral molding.

Next, after drilling a through hole, a conductive layer is formed on the entire surface including the inner wall of the through hole using electroplating, and an outer layer pattern is printed/printed.
A multilayer printed wiring board is manufactured by forming it using an etching process.

[Problem that the invention seeks to solve]

However, the manufacturing of the inner layer substrate of the conventional multilayer printed wiring board described above has the following problems.

That is, when an inner layer pattern is formed on the steel layer of a steel clad laminate by a printing/etching process, local non-etched areas (hereinafter referred to as etching residues) may occur in the steel layer parts that should be etched due to etching resist residue, etc. When a multilayer printed wiring board is manufactured in that state, the through-hole conductor layer and the etching residue of the inner layer board may come into contact, resulting in a short circuit failure. For this reason, inspection at the production stage of the inner layer substrate is important, but this inspection generally involves only visual inspection, and it is difficult to completely detect etching residues, so some oversights are inevitable. Furthermore, even if the defective short-circuit between the through-hole conductor layer and the inner layer pattern is found after the multilayer printed wiring board is manufactured, it is impossible to repair the defect because it is located in the inner layer, and the board is discarded.

In particular, this short-circuit failure has become an important problem in response to the recent demand for a higher number of layers in multilayer printed wiring boards.

[Means for solving problems]

An object of the present invention is to provide a method for repairing a multilayer printed wiring board that solves the conventional problem of short-circuiting between the through-hole conductor layer and the inner layer pattern.

That is, according to the present invention, the step of drilling a first through-hole in a through-hole having a short-circuit defect with a drill having a diameter larger than that of the through-hole and having an outer diameter within a range that does not expose the inner layer pattern in the normal position. a step of filling the first through hole with a thermosetting resin and curing it by heating; and drilling a second through hole in the thermosetting resin filling hole with a drill having the same diameter as the first through hole. forming a resist film for electroless plating except for the inner wall of the second through hole and the front and back lands; and applying electroless plating to the entire multilayer printed wiring board on which the resist film for electroless plating has been formed. a step of forming a catalyst layer for electroless plating, and a step of forming a conductor layer by electroless plating on the inner wall of the second through hole and the front and back lands after removing the catalyst layer for electroless plating on the surface, and A method for repairing a multilayer printed wiring board is obtained, which comprises a step of dissolving and removing a plating resist film.

〔Example〕

Hereinafter, embodiments of the present invention will be described using a four-layer multilayer printed wiring board with reference to the drawings.

FIG. 1(A) is a cross-sectional view of a multilayer printed wiring board with a four-layer structure showing short-circuit defects between the through-hole conductor layer and the inner layer pattern. It has a power layer 2 and a ground layer 3 as well as a three-layer pattern, and a pattern 4 on the front and back surfaces of the insulating plate 10.
, 5 are connected by a through-hole conductor layer 6 made of steel plating or the like.

In this case, the through-hole conductor layer 6 is originally the inner layer power supply layer 2.
Although the through hole is not connected to the ground layer 3, it is short-circuited with the ground layer 3 of the inner layer pattern due to the etching residue 7 of the ground layer 3.

FIG. 1(B) is a plan cross-sectional view of this state taken along the line A-A' in FIG. 1(A). The ground layer 3 and the through-hole conductor layer 6 are short-circuited due to the etching residue 7 in the inner layer 7. First, a multilayer printed wiring board having such a short-circuited portion is constructed as shown in Figure 1 (
As shown in C), the through-hole conductor layer 6 is re-drilled using a drill whose diameter is larger than the outer diameter of the through-hole conductor layer 6 and smaller than the clearance diameter of the ground layer 3. A through hole 8 is formed by removing a portion of the insulating plate 1 along the conductor layer 6.

Next, a thermosetting resin 9 having insulation and heat resistance, such as epoxy resin, is filled into the through hole 8 and cured by heating at a temperature of 80 to 150° C. for 30 to 90 minutes (FIG. 1(D)).

Next, as shown in FIG. 1(E)K, a through hole 10 is made again in the through hole 8 filled with thermosetting resin 9 using a drill having the same diameter as the inner diameter of the first through-hole conductor layer 6, and the inner wall is filled with thermosetting resin. A film of resin 9 is left.

Next, a dry film type electroless plating resist such as DuPont Berkrel 168 is laminated.
The resist film 11 for electroless plating is formed by providing relief in the form of a reverse land so that the pattern 4.5 on the front and back surfaces of the insulating plate 1 is exposed in the form of a land through successive processes of exposure and development (Fig. 1). (F)).

Next, in order to make the through holes 10 conductive, the entire multilayer printed wiring board is immersed in an electroless plating catalyst aqueous solution of a non-metal colloid aqueous solution such as a steel metal colloid aqueous solution, and the entire surface including the inner wall of the through hole 10 is catalytically activated. Catalyst layer 12 for electroless plating
(Fig. 1 (G)).

Next, the surface is washed and polished using a sponge or the like to remove the catalyst layer 12 for electroless plating on the surface, so that the catalyst layer 12 for electroless plating remains only on the thermosetting resin 9 on the inner wall of the through hole 10. (Figure 8g1 (H)).

Next, the through-hole conductor layer 6 is immersed in an electroless steel plating solution at a liquid temperature of 70° C. to form a VT-free copper plating conductor layer only on the inner wall of the through hole 10 and the conductor layer 6a exposed on the surface. Similarly, the through-hole conductor layer 13 is restored and formed (FIG. 1(1)).

Next, the resist coatings 11 for electroless plating on the front and back surfaces are dissolved and removed using a solvent such as methylene chloride to obtain a multilayer printed wiring board of the present invention (FIG. 1 (J)).

〔Effect of the invention〕

As explained above, the present invention has the following effects.

(1) Since the defective short-circuit between the through-hole conductor layer and the inner layer pattern is removed and repaired, there is no need to remanufacture the multilayer printed wiring board by discarding it.

(11) Since the inner wall of the through hole at the repaired location is coated with a thermosetting resin having insulation and heat resistance, high reliability can be maintained.

In this embodiment, a multilayer printed wiring board with a four-layer structure has been described, but it goes without saying that the present invention can also be applied to a multilayer printed wiring board with a larger number of layers.

In addition, in this example, the etching residue within the inner layer clearance was explained, but when the inner layer board and the outer l# board are integrally molded via prepreg and laminated, conductive foreign matter may be mixed into the inner layer clearance. The present invention can also be applied to insulation defects and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A to 1J are a cross-sectional view and a plan view showing the method for repairing a multilayer printed wiring board according to the present invention in the order of steps. 1... Insulating plate, 2, 3, 4.5... Conductor layer, 6, 6L. 13...Through hole 4 layers, 7...Etching remaining, 8.10...(by drilling)
Through hole, 9...-Thermosetting resin, 11...-
- Resist film for electroless plating, 12... Catalyst layer (for electroless plating). Agent: Susumu Uchihara, Patent Attorney - Figure 1 (Fig. 1)

Claims (1)

[Scope of Claim] A method for repairing a multilayer printed wiring board, comprising the following steps. (a) Drill the first through-hole with a drill that has a larger diameter than the through-hole hole and an outer diameter within a range that does not expose the inner layer pattern in the normal position. (a) Filling the first through-hole with a thermosetting resin and curing it by heating; (c) Filling the first through-hole with the thermosetting resin under the through-hole. A step of drilling a second through hole with a drill having the same diameter as the hole; (d) A step of forming an electroless plating resist film except for the inner wall of the second through hole and the front and back lands; (e) Forming a catalyst layer for electroless plating on a multilayer printed wiring board on which an electrolytic plating resist film has been formed; (f) After removing the catalyst layer for electroless plating on the surface of the multilayer printed wiring board, forming the second through-hole A step of forming a conductor layer on the inner wall of the hole and the front and back lands by electroless plating; (g) A step of dissolving and removing the electroless plating resist film.