JP3228914B2 - Laser residual film removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing a laser residual film, and more particularly, to forming an insulating layer formed on a lower circuit board when a multilayer circuit board is manufactured by a build-up method. The present invention relates to a method for removing a laser residual film that can reliably remove a laser residual film remaining in a laser via formed by laser irradiation, regardless of the type of insulating resin.

[0002]

2. Description of the Related Art With the increasing demand for miniaturization, weight reduction, high functionality, and low cost of electric and electronic devices, recently, multilayered circuit boards manufactured by a build-up method have been incorporated into these devices. It is becoming. This is because the multilayer circuit board manufactured by the build-up method enables higher-density wiring than a conventional multilayer circuit board manufactured by a subtractive method or a semi-additive method.

The build-up method generally proceeds as follows. First, as shown in FIG. 1, a circuit board 1 having a predetermined circuit pattern 1B formed on a surface of an insulating base 1A is prepared as a core board. Next, a predetermined insulating resin is applied to the surface of the core substrate 1 to form an insulating layer 2A having a predetermined thickness in which the circuit pattern 1B is embedded (FIG. 2).

At a predetermined position of the insulating layer 2A, as shown in FIG. 3, a recess 1C is formed up to the surface 1b of the circuit pattern 1B of the core substrate 1, and an intermediate material I is manufactured. . The recess 1 </ b> C is converted into an inner via hole connecting the lower circuit board and the upper circuit board through a process described later. The recess 1C may be formed by a combination of photolithography and etching, but is more often formed recently by laser irradiation. According to the laser irradiation, it is possible to make the hole diameter of the concave hole 1C extremely small.
This is because high-density circuit patterns in each layer can be wired.

As a laser, a carbon dioxide gas laser, a YAG laser, an excimer laser, or the like is used. However, a carbon dioxide gas laser is generally used because the processing speed of a concave hole is high and the productivity in manufacturing a substrate can be increased. It is a target. In the following description, it is assumed that the above-described recess 1C is formed by laser irradiation, and the recess is hereinafter referred to as a laser via.

After the surface of the intermediate material I is usually subjected to a surface roughening treatment, for example, electroless copper plating and electrolytic copper plating are successively performed on the formed roughened surface, so that the insulating layer 2A and the inner wall of the laser via 1C are removed. An intermediate material II is manufactured by forming a conductor plating layer 2B having a predetermined thickness to cover (FIG. 4). This intermediate material II
At the bottom of the laser via 1C, it is necessary that the conductive plating layer 2B and the surface 1b of the circuit pattern 1B of the core substrate 1 be in close contact with each other.

[0007] Then, on the surface of this intermediate material II perform photolithography and etching, to produce an intermediate material III to form a predetermined circuit pattern and the inner layer via holes C ₁ on the insulating layer 2A (Fig. 5). In this intermediate material III, an insulating layer 2 is formed on a lower circuit board 1 which is a core board.
A and a circuit board 2 on which a circuit pattern composed of a conductor plating layer 2B is formed has a two-layer structure,
Between each layer has a connection structure in the inner via hole C _1.

After an insulating layer is further formed on the intermediate material III, the method described with reference to FIGS.
If another circuit board is formed, a multilayer circuit board having a three-layer structure can be obtained. When the intermediate material I is manufactured by forming the laser via 1C in the insulating layer 2A, as shown in FIG. 6, the insulating layer 2C is formed on the surface 1b of the circuit pattern 1B.
A thickness 1 which is an insulating resin constituting A or a thermally altered substance thereof
The residual film 2C of about 2 μm may remain. This tendency is particularly strong when a carbon dioxide laser is used.

If the process is advanced to the production of the next intermediate material III in a state where the laser residual film 2C remains, no conductor plating layer is formed on the surface 1b. As a result, the intermediate material III is not formed. Inner via hole C formed in
₁ loses the function of connecting the layers. Therefore, it is necessary to remove the laser residual film, and for that purpose, the following processing has conventionally been adopted. A typical example will be described below.

First, a swelling process is performed on the intermediate material I on which the laser via 1C has been formed. Specifically, using an aqueous solution in which sodium hydroxide is mixed in a solvent such as ethers, alcohols and pyrrolidone, the temperature is 30 to 5;
Dipping or jet spraying is performed at 0 ° C. for a processing time of about 1 to 10 minutes. As a result, the resin structure is opened, softened, or swelled, so that alkali etching performed in the next step is easily performed.

Next, an alkali etching process is performed. Specifically, immersion or jet spraying is performed using a permanganate (usually K or Na salt) alkali aqueous solution at a temperature of 60 to 80 ° C. for a processing time of about 2 to 30 minutes. As a result, the laser residual film 2C is removed by etching.
The surface 1b of the circuit pattern 1B is exposed there. By this treatment, the surface of the insulating layer 2A and the inner wall of the laser via 1C are also removed by about 1 to 2 μm. This is because the thickness of the insulating layer 2A and the hole diameter of the laser via 1C are designed in consideration of the removal amount. If it does, no inconvenience will occur.

Finally, a neutralization treatment is performed. Specifically, immersion or jet spraying is performed using a reducing acidic aqueous solution such as an amine compound at a temperature of 30 to 50 ° C. for a processing time of about 1 to 20 minutes. As a result, the insulating layer 2A
The manganese acid and manganese oxide remaining there are reduced and dissolved on the surface of the substrate and the inner wall of the laser via 1C, and the surface is completely removed to obtain a clean surface.

[0013] In between the above-mentioned processes, it goes without saying that the processing material is washed, for example, with water to remove the chemical solution used in the preceding process.

[0014]

However, the build-up method of forming a laser via in an insulating layer using a carbon dioxide laser has the following problems. First, a general problem is that a laser residual film is easily generated as described above. If a YAG laser or an excimer laser that oscillates a laser beam with a shorter wavelength is used, a laser residual film will not occur. However, these lasers have a problem that the processing time of the laser via is long and the productivity is low. Therefore, from the viewpoint of a manufacturer that manufactures a multilayer circuit board by the build-up method, it can be said that it is industrial to select the use of a carbon dioxide laser for economic reasons.

On the other hand, there is the following problem. First, the following functions are required of the insulating layer in the multilayer circuit board. That is, the most important function is to provide insulation between the upper layer and the lower layer. When the intermediate material II is manufactured from the intermediate material I, for example, the roughened insulating layer 2
A is an insulating layer having a high adhesion strength between the surface of the conductive layer A and the conductive plating layer 2B.
For example, the insulating layer is such that C can be easily formed.

Therefore, in order to make the insulating layer 2A fulfill these functions, the insulating resin constituting the insulating layer 2A includes:
Various things are used and are not unique. Also,
Depending on the use of the multilayer circuit board for manufacturing purposes, the insulating layer 2A
The type of the insulating resin used for is changed. However, the change in the constituent resin of the insulating layer 2A means that in the step of removing the laser residual film 2C remaining in the intermediate material I, the chemical solution or treatment used in the above-described swelling, etching, and further neutralization treatments It is necessary that the conditions have to be selected in each case corresponding to the constituent resins.

That is, regarding the removal of the laser residual film,
Separate processing lines are required depending on the type of constituent resin of the insulating layer 2A, which leads to an increase in equipment costs as a whole, which is very uneconomical. The present invention solves the above-described problem in the conventional laser residual film removal process, and can reliably remove the laser residual film in one processing line even if the type of insulating resin forming the insulating layer changes. It is an object of the present invention to provide a method for removing a residual laser film.

[0018]

In order to achieve the above object, according to the present invention, when a multilayer circuit board is manufactured by a build-up method, an insulating layer formed on a lower circuit board is formed. In a method of removing a laser residual film remaining in a laser via formed by laser irradiation,
A degreasing process on the laser via; a first etching process on the laser via after the degreasing process; a swelling process on the laser via after the first etching process; a second etching process on the laser via after the swelling process; 2. A method for removing a laser residual film, which comprises sequentially performing a neutralization process on the laser via after the etching process of 2.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, first, an intermediate material having a laser via formed therein is immersed in the following chemical solution to perform a degreasing treatment on the laser via. The chemicals used include the following two types of A and B as essential components. A is
A mixture of methanol-based amines that acts as a copper complexing agent. B is a polyethylene glycol type or polyhydric alcohol type nonionic surfactant, which functions to remove oily contaminants on the resin surface and to penetrate the resin.

In this chemical solution, the concentrations of A and B are preferably set to 1 to 10 g / L and 0.5 to 10 g / L, respectively. As a result of this degreasing, the laser residual film 2C shown in FIG. 6 is in a state of liquid permeation up to the boundary with the surface 1b of the circuit pattern 1B. Next, a first etching process is performed.

For example, sulfuric acid 100 mL / L, hydrogen peroxide 6
Using a chemical solution consisting of 0 mL / L, oxalic acid 5 g / L, and the balance being pure water, etching is performed at a temperature of 30 ° C. for a processing time of 90 seconds. By the first etching process, the laser residual film 2C is in a state of being slightly peeled at the boundary with the surface 1b of the circuit pattern 1B.

After the first etching process, the conventional swelling process, the etching process (corresponding to the second etching process in the present invention), and the neutralization process are performed on the laser via in this order. Done in

[0023]

EXAMPLE An epoxy resin was applied to the surface of a copper-clad laminate to form an insulating layer having a thickness of 60 μm. The surface of the insulating layer is irradiated with a carbon dioxide gas laser so that the upper opening diameter is 100 mm.
μm, 100 laser vias with a bottom opening diameter of 80 μm /
It was formed at a density of mm ^2. Then, under the following conditions,
Degreasing, first etching, swelling, second etching, and neutralization were sequentially performed.

Degreasing treatment: triethanolamine 5% by weight, polyoxyethylene alkyl ether 3% by weight, oxo alcohol ethylene oxide 8.5 mol adduct 2
% Aqueous solution of 4% by weight of sodium hydroxide
It was immersed at 5 ° C for 5 minutes. First etching treatment: An aqueous solution containing 10% by weight of ammonium persulfate and 4% by weight of tetrasodium edetate tetrahydrate at a temperature of 2%
It was immersed at 5 ° C. for 50 seconds.

Swelling treatment: 50% by weight of diethylene glycol n-butyl ether, 20% by weight of diethylene glycol monomethyl ether, 15 g / L of sodium hydroxide,
Polyethylene glycol laurate diester 3% by weight
Was immersed in an aqueous solution at a temperature of 65 ° C. for 5 minutes. Second etching treatment: potassium permanganate 50 g /
L, aqueous solution of sodium hydroxide 40 g / L, temperature 70
C. for 10 minutes.

Neutralization treatment: glyoxal dialdehyde
It was immersed in an aqueous solution of hydroxylamine sulfate 40% by weight and sulfuric acid 50 mL / L at a temperature of 40 ° C. for 5 minutes. Next, copper plating with a thickness of 25 μm was applied to the surfaces of the insulating layer and the laser via. With respect to the obtained member, the peel strength of the plating layer was measured according to the following specifications.

Measurement of peel strength: An Autograph RCT-5K manufactured by Shimadzu Corporation was used as a measuring device. Tension in 90 ° direction, pulling speed 5 mm / min, width of copper plating layer 1.
Measured under the condition of 27 mm. The result is 1.80 kg / c at maximum
m, the minimum value was 1.45 kg / cm, and the average value was 1.65 kg / cm.

For comparison, the insulating layer and the laser via were formed in the same manner as in the embodiment except that the above-described degreasing and the first etching were not performed, and the laser residual film processing was started from swelling. A copper plating layer having a thickness of 25 μm was formed on the surface, and the peel strength was also measured. As a result, the maximum value was 1.60 kg / cm, the minimum value was 1.10 kg / cm, and the average value was 1.33 kg / cm.

As is clear from both results, in the case of the embodiment in which the degreasing treatment and the first etching treatment were performed, the peel strength of the plating layer was improved by 20% or more as compared with the comparative example. It can be seen that the removal of the residual film has been ensured.

[0030]

As is apparent from the above description, the method of the present invention employs a degreasing treatment, a degreasing treatment, and a dehydration treatment prior to a series of swelling, etching, and neutralization treatments applied to the removal of a laser residual film. By performing the etching process 1, even if the constituent resin of the insulating layer is different, the laser remaining film can be surely removed, and the degree of freedom in the method of manufacturing the multilayer circuit board by the build-up method can be increased.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing an example of a core substrate used in a build-up method.

FIG. 2 is a partial cross-sectional view showing a state where an insulating layer is formed on the core substrate of FIG.

FIG. 3 is a partial cross-sectional view showing an intermediate material I in which a laser via is formed in the insulating layer of FIG. 2;

FIG. 4 is a partial cross-sectional view showing an intermediate material II in which a conductor plating layer is formed on a laser via of the intermediate material I of FIG. 3;

FIG. 5 is a partial cross-sectional view showing an intermediate material III in which a second circuit board is formed on a core board.

FIG. 6 is a partial cross-sectional view showing a laser residual film in a laser via.

[Explanation of symbols]

1 the first circuit board (core board) of 2 second circuit board 1A, 2A insulating layer 1B, 2B conductor plating layer 1C Rezabaia 2C laser residual C ₁ inner via holes

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI H05K 3/26 H05K 3/26 B (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 3/00 H05K 3 / 26 H05K 3/46 B23K 26/00

Claims (3)

(57) [Claims] 1. A laser residual film remaining in a laser via formed by irradiating a laser to an insulating layer formed on a lower circuit board when a multilayer circuit board is manufactured by a build-up method. In the method of removing, a first etching process on the laser via after the degreasing process; a swelling process on the laser via after the first etching process; a second etching on the laser via after the swelling process And a neutralization process for the laser via after the second etching process. 2. The method according to claim 2, wherein the degreasing treatment comprises triethanol alcohol.
Min 5% by weight, polyoxyethylene alkyl ether 3
Weight percent, 8.5 moles of oxo alcohol ethylene oxide
Aqueous solution of 2% by weight of adduct and 4% by weight of sodium hydroxide
2. The laser according to claim 1, wherein the laser is immersed in the device at a temperature of 45 ° C. for 5 minutes.
How to remove residual film. 3. The method according to claim 1, wherein the first etching treatment is
Ammonic acid 10% by weight, edetate tetrasodium tetrahydrate 4
Immersion in a 25 wt% aqueous solution at a temperature of 25 ° C for 50 seconds
Item 4. A method for removing a laser residual film according to Item 1.