JPH0219997B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a method for manufacturing a multilayer wiring board by the addi-dive method.

Conventional technology A multilayer wiring board is made by laminating an inner wiring board with wiring patterns on both sides and a copper-clad laminate using a lamination press method with prepreg interposed therebetween. After plating, an etching process is performed to remove unnecessary copper foil and form an outer layer circuit.

Recently, after drilling through-holes, seeders are attached using seeder treatment, and when forming an insulating layer, a plating catalyst is added to the insulating resin. A method has been developed to form a through-hole circuit using only a laminate.
Furthermore, a method has been developed in which outer layer circuits and through holes are simultaneously formed only by electroless plating.

Problems to be Solved by the Invention An important characteristic of a multilayer wiring board is the reliability of through holes. In particular, the reliability of conduction between the inner layer copper foil and the through-hole plating within the through-hole is important. The insulating resin 6 melts under the influence of the heat generated when drilling 7 into the element that most affects the reliability of the through-hole, and the insulating resin 6 adheres to the cut end surface of the inner layer copper foil 4 (called smear). ) If this smear 8 remains, it will impair the conductivity between the inner layer copper foil 4 and the through-hole copper 15, and if the cooling/heating cycle is repeated, it will cause an accident where the plating breaks. On the other hand, since the smear treatment liquid used when removing smear has a dissolving effect on copper, the inner layer copper foil 4 is eroded and retreats from the surface of the hole 7 (referred to as an etched back) to the inside, creating a defective part 9A. It becomes an obstacle when forming through holes by plating. Therefore, there are usually few etched backs,
In addition, conditions are required to ensure smear removal.

Means for Solving the Problems The present invention involves sequentially laminating an insulating layer and an adhesive layer on an inner layer wiring board, further forming a plating resist layer, and then drilling holes for through holes. When removing smear with a processing solution, some smear remains, and the inner layer copper foil is treated with a solution that dissolves it, forming a defective part on the end surface of the inner layer copper foil facing the hole for the through hole, and removing the through hole. This is a method of manufacturing a multilayer wiring board that performs copper plating treatment to form holes and outer layer circuits.

As a solution for dissolving the inner layer copper foil, an HBF tetrachlorine dichromate solution or a NaF, H ₂ SO ₄ , CrO ₃ based solution is used, and as a smear treatment liquid, an alkaline solution of KMnO ₄ or concentrated sulfuric _acid is used.

Examples Example 1 Glass base epoxy resin 1 and catalyst-containing adhesive 2
is coated, an inner layer copper foil 4 is formed in the area excluding the plating resist 3, an insulating layer 6 and an adhesive layer 12 are formed thereon, and after drilling holes 7 for through holes with a drill, smearing is performed. 8 to potassium permanganate 50
It was immersed for 10 minutes at 60℃ in a smear treatment solution consisting of CrO 3 /30g/, and CrO ₃ 40g/
, H ₂ SO ₄ 350 g/, NaF 35 g/ for 15 minutes at 30° C., so that the inner layer copper foil 4 is coated at least on the end surface of the inner layer copper foil facing the through-hole hole 7, as shown in FIG. An end face shape was formed in which a tapered defect portion 9B was formed with a portion of 4A remaining. Thereafter, a seeder treatment was performed, and the multilayer wiring board 20 was manufactured by immersing it in an electroless plating solution to form through holes 15 and outer layer copper foil 14.

Example 2 In Example ₁ , _{HBF 4 550} g/, Na ₂ Cr ₂ O ₇ 25 g/
As shown in FIG. 6, at least a part of the end surface 4A of the inner layer copper foil 4 facing the hole 7 for the through hole is left in the tapered defect area. Example 1 except that 9B was formed.
A multilayer wiring board was manufactured using the same manufacturing method.

Comparative Example 1 Using the same smear treatment liquid as in Example 1,
Treatment was performed at 60°C for 25 minutes. After the smear 8 was completely removed, the through holes were copper plated.

Multilayer wiring boards manufactured by the manufacturing methods of the above examples and comparative examples were heated in hot oil (260°C, 10 seconds).
A thermal shock test was conducted using As a result, the number of cycles in which the resistance value of the through hole exceeded 10% was Example 1, 60 cycles, Example 2, 55 cycles, Comparative Example 1, and 40 cycles. The reliability of connection with circuit 4 has been improved. When a destructive test was performed, all of the defects occurred at the interface between the inner layer copper 4 and the through-hole copper 15.

Effects of the Invention According to the method for manufacturing a multilayer wiring board of the present invention, the connection between the inner layer copper foil and the through-hole copper foil was strengthened, and a highly reliable wiring board was obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a wiring board manufactured by the method of the present invention, FIG. 2 is a sectional view of an inner layer wiring board, FIGS. 3 and 4 are sectional views showing a conventional manufacturing method, and FIG.
The figure shows the state before smearing, FIG. 4 is a sectional view after smearing, FIGS. 5 and 6 show the present invention, and FIG. FIG. 6 is a sectional view showing a state in which the end face of the inner layer copper foil is etched back after being treated with the inner layer copper foil treatment liquid. In the drawings, 1: insulating substrate, 4: inner layer copper foil,
6: Insulating layer, 7: Drilling, 8: Smear, 9: Defect part, 10: Inner layer wiring board, 14: Exterior copper foil, 20:
Multilayer wiring board.

Claims (1)

[Claims] 1 Form an insulating layer and adhesive on the inner layer wiring in sequence,
After forming a plating resist layer, holes are drilled for through holes, and smear treatment liquid is applied to
Smearing was performed at 60°C for 10 to 15 minutes with some smear remaining, and the inner layer copper foil was treated with a solution that dissolves it to leave at least a portion of the end face of the inner layer copper foil facing the hole for the through hole. 1. A method for manufacturing a multilayer wiring board, which comprises forming a tapered defect in a state, and then performing a copper plating process to form a through hole and an outer layer copper foil.