KR100332971B1 - Blind via hole formation method on build-up pcb - Google Patents

Abstract

PURPOSE: A method for manufacturing a blind via hole of a build-up PCB(Printed Circuit Board) is provided to increase the adhesion force and quality of plating by removing residues on a pattern of a lower PCB through a sulphuric acid containing a surface active agent and performing the removal of the residues through an oxidant upon forming the blind via hole. CONSTITUTION: A blind via hole is formed(ST200). The blind via hole has the depth from an upper build-up PCB to a lower build-up PCB. An ion material is injected into the blind via hole in order to remove residues of an insulating layer that is adhered on a pattern after forming the blind via hole(ST300). The ion material is a mixture of a surface active agent and an oxidant. An oxidant is injected into the residues of the insulating layer, which remain on the pattern after the injection of the ion material, to thereby remove them(ST400,ST500). A neutralizer is added to the blind via hole that is acidified by the injection of the oxidant, to thereby neutralize the blind via hole acidified(ST600). The neutralized blind via hole is plated(ST700).

Description

Blind Via Hole Formation Method for Stacked PCBs {BLIND VIA HOLE FORMATION METHOD ON BUILD-UP PCB}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a build-up PCB, and more particularly, to a method of forming blind via holes in a stacked PCB to electrically conduct a pattern of an upper substrate and a pattern of a lower substrate.

Stacked PCB substrates can be realized by stacking a single PCB substrate in one or more layers and connecting patterns of the stacked layers to each other according to a purpose, thereby reducing the area and increasing the density of the PCB substrate.

As a result, the PCB substrate has been downsized and is widely used in portable electronic equipment and communication equipment such as mobile phones, portable small cassettes, and the like, in which components are mounted at high density.

In order to connect the patterns formed in the stacked layers of the stacked PCB substrates, that is, the wirings, to each other, blind via holes are formed and connected to each other, which will be described with reference to FIG. 1.

First, the upper PCB 100 is laminated on the lower PCB 100 of the insulator material such as epoxy on which the pattern 101 is formed, and then the blind via hole is inclined by burning the epoxy portion of the upper PCB 110 by a laser drill. And form 112.

In this case, the blind via hole 112 has a depth up to a portion where the pattern 101 of the lower PCB substrate 100 is formed, and only an epoxy portion of the upper PCB substrate 110 is burned by a laser drill, and copper The pattern 101 portion of the lower PCB substrate 100 formed by the substrate is not burned or the copper and the insulating layer are burned at the same time to form the blind via hole 112.

Accordingly, the plating process is performed on the portion where the blind via hole 112 is formed in this manner so that the pattern 101 of the pattern 111 of the upper PCB substrate 110 and the pattern 101 of the lower PCB substrate 100 are mutually formed by the plating portion 113. Since the side wall of the blind via hole 112 is inclined, the plating liquid flows easily to the pattern 101 portion of the lower PCB substrate 100, and plating is performed, and the plating area is widened to increase adhesion.

This process is repeated to continue stacking PCBs.

However, when the blind via hole 112 is formed by a laser drill, as shown in FIG. 2, the burned insulating layer residue 114 burns on the pattern 101 of the lower PCB substrate 100. It hardens and hardens on the surface.

When plating is performed without removing the dregs 114, the plating is not easily performed, and thus the signal transmission force between the patterns 101 and 111 is reduced, and the plating is easily peeled off, thereby increasing the defect rate of the laminated PCB substrate and increasing reliability. Will fall.

Therefore, a process of removing the debris 114 is required. In the related art, a sweller is injected into the blind via hole 112 to deposit debris 114 deposited on the pattern 101 of the PCB 100. Swelling softens the hardened state.

Thereafter, the softened dregs 114 are removed using a strong oxidizing agent such as potassium permanganate (KMnO 4), and then the acidified blind via holes 112 and the pattern 101 are removed during the process of removing the dregs 114. Neutralizing agent is injected to neutralize the electroless copper plating to set the conditions of the next process.

Therefore, the neutralized blind via hole 112 is plated to electrically connect the pattern 111 of the upper PCB substrate 110 and the pattern 101 of the lower PCB substrate 100.

However, even after such a process, the residue deposited on the blind via hole is not completely removed and the plating cannot be used. Therefore, the adhesion is reduced and the plating is easily lifted, so that the signal transmission power is lowered and the defect rate is high. In addition, due to the drop in signal transmission power, the number of stacking of the PCB is limited, and thus there is a problem in that the size of the PCB is reduced.

Accordingly, in view of the above problems, the present invention injects sulfuric acid containing a water-soluble surfactant into the insulating residue left in the blind hole to remove it first, then swell and remove the residue secondly by potassium permanganate. SUMMARY OF THE INVENTION An object of the present invention is to provide a blind via hole forming method of a laminated PCB to increase plating adhesion by increasing the removal efficiency.

In order to achieve the above object, the present invention provides a method of forming a blind via hole of a stacked PCB, including forming a blind via hole having a depth from a stacked upper PCB to a pattern of a lower PCB; A first residue removing step of injecting an ionic material into the blind via hole to remove the insulating layer deposit deposited on the pattern after the hole forming process; A second residue removing step of removing the residue by injecting a sweller and an oxidizing agent into the epoxy residue remaining after the first residue removing process; Neutralization by adding a neutralizing agent to the blind via hole acidified by the second removal process; The neutralized blind via hole is characterized in that the plating process for electroless copper plating.

1 is a view showing a blind hole formed on a typical laminated PCB substrate.

2 is a view for explaining a conventional swelling process for forming a blind hole.

3 is a view for explaining a blind hole forming process of the present invention.

4 is a view showing a blind hole forming method of the laminated PCB of the present invention.

<Explanation of symbols for main parts of the drawings>

200,210: PCB substrate 201,211: pattern

212: blind via hole 213: residue

214: etch back portion 215: plating portion

Hereinafter, the present invention will be described in detail with reference to FIGS. 3 and 4.

In the present invention, a method of forming a blind via hole in a multilayer PCB substrate includes hole formation processes (ST100 and ST200), primary debris removal (ST300), secondary debris removal (ST400 and ST500), neutralization process (ST600), The plating process (ST700) is made.

In the hole forming process (ST100, ST200), the upper PCB substrate 210 is stacked on the lower PCB substrate 200 on which the pattern 201 is formed, and then the lower PCB substrate 200 is removed from the upper PCB substrate 210 using a laser drill. Process of forming the blind via hole 212 having a depth up to the pattern 201.

The first debris removal process ST300 is a process of primary removal of the debris deposited on the pattern 201 of the lower PCB substrate 200 exposed on the inner bottom surface of the blind via hole 212 by injecting an ionic material.

The ionic material used here is a mixture of sulfuric acid and a surfactant (1% of the surfactant in 99% sulfuric acid).

The secondary debris removal process (ST400, ST500) is a process of swelling and removing the remaining debris by using a strong oxidizing agent without being completely removed by the primary debris removal process (ST300).

The neutralization process ST600 is a process of removing acid groups remaining in the blind via hole 212 by the neutralizing agent after the second removal processes ST400 and ST500.

The plating process ST700 is a process of plating the blind hole 212 to electrically connect the pattern 211 of the upper PCB substrate 210 and the pattern 201 of the lower PCB substrate 200 with a conductive material to electrically connect the pattern. to be.

This will be described in detail.

First, the upper PCB substrate 210 is laminated on the lower PCB substrate 200 formed of the insulator on which the pattern 201 is formed, and then the insulator portion of the upper PCB substrate 200 is patterned by the laser drill on the lower PCB substrate 200. The blind via hole 112 is formed by burning until 201 is exposed. At this time, the sidewalls of the blind via hole 112 are not formed to be inclined as in the related art, and are formed to be nearly perpendicular to each other (ST100, ST200). .

In this case, the residue 213 of the insulator is cured and welded on the pattern 201 of the lower PCB substrate 200 that is exposed during the formation of the blind via hole 112.

In order to remove this, a solution mixed with a surfactant and sulfuric acid is first injected into the residue 213, and the residue 213 cured by the strong oxidizing power of the sulfuric acid component is desorbed to some extent, in particular, a surfactant. By the ionic effect to increase the desorption of the residue 213 by (ST300).

At this time, the slope of the sidewall is retracted by the strong sulfuric acid to form an etch back portion 214, which is to maintain the desired hole shape by adjusting the slope of the sidewall when forming blind via holes. to be.

That is, it has a moderately inclined sidewall of the blind via hole 212 to increase the ease of plating and adhesion.

Therefore, although the residue is first removed by the surfactant and sulfuric acid, but the residue 213 that is not completely removed by the removal process has to remove the residue once again, using a powerful sweller, the lower PCB substrate 200 Swelling the residue 213 deposited on the pattern 201 of the ()) to soften the hardened state.

Thereafter, the swelled debris 213 is removed using a strong oxidizing agent such as potassium permanganate (KMnO 4), and then the acidized blind via hole 212 and the pattern 201 are removed during the process of removing the debris 213. It is neutralized by injecting a neutralizer so that it can be neutralized.

Therefore, the residue is removed in two steps, and then the neutralized blind via hole 212 is plated with a conductive material so that the pattern 211 of the upper PCB substrate 210 and the pattern 201 of the lower PCB substrate 200 are removed. ) Is electrically connected.

As described above, in the method of forming blind via holes of the multilayer PCB substrate of the present invention, the residues remaining on the pattern of the lower PCB substrate during the formation of the blind via holes are first removed by using sulfuric acid containing a surfactant and then once again removed by an oxidizing agent. By improving the area and adhesion of the plating, it is possible to make excellent defect rate and signal transmission power, prevent signal disconnection and increase the number of stacking of the PCB, so that the system can be made more compact and dense. There is.

Claims (2)

A hole forming process of forming a blind via hole having a depth from a stacked upper PCB substrate to a pattern of a lower PCB substrate; A first debris removing step of injecting an ionic material mixed with a surfactant and an oxidizing agent into the blind hole to remove the insulating layer deposit deposited on the pattern after the hole forming process; A second step of removing the residue by injecting a sweller and an oxidizing agent into the remaining residue of the insulating layer after the ion implantation process; Neutralization by adding a neutralizing agent to the blind via hole acidified by the second removal process; A method of forming blind via holes for a multilayer PCB substrate, characterized in that the plating process is performed by electroless copper plating on the neutralized blind holes. The method of claim 1, wherein the blind via hole is formed in the hole forming process so that sidewalls thereof are formed at right angles.