JPH0328389A - Copper foil layer for copper-clad laminate, its production and plating bath used therefor - Google Patents

Abstract

PURPOSE:To produce a copper foil layer for a copper-clad laminate having a high adhesive strength to an insulating substrate by plating the surface of a copper plating layer formed on copper foil with a copper plating bath contg. metal such as zinc under specified conditions to form the roughened surface having a thermal deterioration preventing layer. CONSTITUTION:A copper plating layer is formed on the surface of the copper foil or conductive substrate. A copper plating bath contg. at least one kind selected among a group of zinc, tin and cobalt is brought into contact with the surface of the copper plating layer at the contact velocity of 0.3-0.7m/sec, and the surface is plated at 30-55A/dm<2> current density. Consequently, a copper foil layer with the roughness of the surface controlled to <=7mu and the variance in roughness limited within + or -0.5mu of the mean roughness is obtained. The adhesion to the insulating layer is increased, and a remaining in the depth part at the time of etching is reduced.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is an adhesive that has a small surface roughness on a matte surface that is thermocompression bonded to an insulating base material during the production of copper-clad laminates, and has small variations in the roughness. The present invention relates to a copper foil layer having a surface, a method for producing the same by electrolytic plating, and a plating bath used in the method.

(Prior art) Copper-clad laminates, which are the basic material for printed wiring boards incorporated in various electronic devices, are made by forming conductor circuits on the surface of an electrically insulating base material such as a glass fiber-epoxy resin composite. It is manufactured by thermocompression bonding a copper foil layer of a predetermined thickness.

In this case, one conventional method is to electrodeposit copper on a rotating drum with a polished surface, which is itself a cathode, to form an electrolytic steel foil of a predetermined thickness, which is then continuously removed from the drum. In this method, the matte side is peeled off and the matte side is thermocompression bonded to the surface of the insulating base material.

Recently, a copper plating layer of a predetermined thickness is formed by electrolytic plating on a veneer of a conductive base material such as a stainless steel plate with a smooth surface, and then the copper plating layer side of the conductive base material is attached to an insulating base material. A transfer method is also widely used in which the steel plating layer is transferred to the surface of the insulating base material by superimposing the steel plate on the surface and bonding the whole body by thermocompression, then peeling off only the conductive base material.

In any of these methods, the copper foil layer such as the electrolytic copper foil or copper plating layer described above is generally subjected to the following surface treatment.

One of them is a treatment for roughening the adhesion surface of the copper foil layer with the insulating base material to increase the adhesion strength with the insulating base material.

Methods used for this treatment include surface roughening by mechanical grinding and surface roughening by etching using chemicals, but recently electrolytic copper plating has been used to deposit dendrites on the surface of the copper foil layer. A method of at least roughening the entire surface into an uneven shape is often used.

Due to this surface roughening, during thermocompression bonding with the insulating base material,
The dendrites are embedded in the matrix resin of the insulating base material and exert an anchor effect, thereby improving the adhesion strength as a whole.

The second treatment is a treatment in which, following the roughening treatment, a thermal deterioration prevention layer is formed on the formed roughened surface.

Generally, the copper foil layer of a copper-clad laminate is subjected to a predetermined masking-etching operation to form a predetermined pattern of conductive circuits. And in this conductor circuit,
Various IC chips and the like are mounted by soldering. Therefore, during this soldering, the conductor circuit and the soldering location at the adhesive interface between the conductor circuit and the insulating base material are partially heated.

As a result, the copper on the roughened surface of the copper foil layer undergoes thermal deterioration, and a situation occurs in which that portion peels off from the surface of the insulating base material.

In this case, for example, substrates used in automobiles are required to have no thermal deterioration even after a 48-hour heating test at 180°C. Considering this, it can be said that the heat deterioration resistance is reasonable.

The thermal deterioration prevention layer is a layer formed to prevent such a situation from occurring and ensure adhesion between the copper foil layer and the insulating base material, and is usually made of brass (Cu-Zn) or Ni-Cu. alloy,
Sn-Cu alloy. It is composed of a composition such as a Sn-Zn-Cu alloy.

This thermal deterioration prevention layer is usually formed by electrolytic plating of a predetermined metal or alloy on the roughened surface of the copper foil layer, or by bonding the thermal deterioration prevention layer with an adhesive. .

The third treatment is rust prevention treatment. The purpose of this treatment is that during the storage and transportation process of manufactured copper-clad laminates, the outer surface of the copper foil layer, that is, the surface opposite to the adhesive surface with the insulating base material, oxidizes and discolors. This is to prevent the appearance of the product from decreasing in value. Generally, chromate treatment is performed.

In view of the above-mentioned purpose, this anti-corrosion treatment only needs to be applied to the outer surface of the copper foil layer.

In this way, in the case of a copper foil layer that is thermocompression bonded to an insulating base material, the bonding surface with the insulating base material has a roughened surface of the unevenness formed on the main copper foil and a surface of this roughened surface. There is a thermal deterioration prevention layer formed as a covering, and if necessary, a rust prevention layer is further formed on top of the thermal deterioration prevention layer.

The protrusion layer that is composed of this roughened surface and the thermal deterioration prevention layer formed thereon is generally called a profile layer. Therefore, this profile layer is
The roughening treatment of the surface of the copper foil layer and the treatment of forming a thermal deterioration prevention layer are each formed by a continuous process combining independent processes.

(Problem to be Solved by the Invention) By the way, in this profile layer, if the height of the protrusion layer protruding from the main copper foil (protrusion height) is too high, that is, the roughness of the bonding surface of the copper foil layer is too large. In this case, when the insulating base material is crimped here, the matrix resin of the insulating base material does not penetrate to the bottom between the respective protrusions, and air bubbles are likely to be trapped in that part. In such a state, poor adhesion between the copper foil layer and the insulating base material will occur. Normally, the height of this profile layer, that is, the surface roughness of the copper foil layer, is about 7 to 9 μm, and the above-mentioned problems often occur, leading to a decrease in the reliability of the copper-clad laminate.

In addition, if the protrusion height in this profile layer varies depending on the location, that is, if the surface roughness of the mesh foil layer varies greatly, a predetermined etching treatment may be performed on the surface of the copper foil layer of the manufactured copper-clad laminate. At this time, among the profile layers buried in the matrix resin, shallowly buried protrusions, that is, profiles with low protrusion heights, are etched away, but the tip portions of the profiles with high protrusion heights are not etched away. They are left as they are in the matrix resin, causing the so-called foot-remaining phenomenon.

If such residual copper (stain) exists, the electrical insulation between the conductor circuits will deteriorate. Particularly, such a phenomenon is a serious problem when forming a conductive circuit pattern with a narrow circuit width, that is, when forming a fine pattern, and may even lead to loss of functionality of the printed wiring board.

To deal with this residual copper problem, measures have been taken to reduce the thickness of the entire copper foil layer. Since the protrusion height and its variation remain at the above-mentioned level, there is still the problem that residual copper is likely to occur when forming a fine pattern.

Thus, to date, regardless of the thickness of the main copper foil, the protrusion height in the profile layer is low, that is, the surface roughness is small, and the variation in the surface roughness is also small. Copper foil layers for copper-clad laminates with profile layers are not known.

The present invention solves the above-mentioned problems with the profile layer, and provides a surface roughness that is small and has little variation, no matter what kind of copper foil it is or whether it is a copper plating layer used in the above-mentioned veneer transfer method. The present invention aims to provide a copper foil layer for a copper-clad laminate having a profile layer with a small adhesive surface, a method for producing the copper foil layer by electrolytic plating, and a plating bath used for the electrolytic plating.

(Means and effects for solving the problem) In order to achieve the above-mentioned object, in the present invention, the roughness of the adhesive surface with the insulating base material is 7 μm or less, and the variation in roughness is equal to the average roughness. Provided is a copper foil layer for a copper-clad laminate, characterized in that the thickness is within ±0.5 μm,
Further, a copper plating bath containing at least l metals selected from the group of zinc, tin, and cobalt is applied to the surface of the copper plating layer formed on the surface of the copper foil or the conductive base material.
3-0. A copper-clad laminate characterized by forming a roughened surface having a thermal deterioration prevention layer by plating at a current density of 30 to 55 A/dm while contacting with liquid at a contact speed of 7 m/sec. A method for manufacturing a copper foil layer for a plate is provided, further comprising a bath composition of copper sulfate (CuSO, .5H.
0) 110-130g/C sulfuric acid (H.SO4) 55-6
5g/l, nitrate ion (No!-) 2 1-2 4 g
/l, at least l compounds selected from the group of zinc compounds, tin compounds, or cobalt compounds 200 to 100
An electrolytic copper plating bath is provided, characterized in that it contains 0 ppm of chelating agent and 5 to 20 g/l of chelating agent.

First, in the copper foil layer of the present invention, the roughness of the adhesive surface with the insulating base material is 7 μm or less. That is, the protrusion height of the profile layer is 7 μm or less. The variation in surface roughness is within a range of ±0.5 μm with respect to the average roughness. That is, when the average value (average roughness) of the protrusion height of the profile layer is a0 μm, the thickness (height of the protrusion height) a of the profile layer is a@-0.5≦a≦as+0. Everything is within the range of 5.

If the roughness is greater than 7 μm, air bubbles may be mixed into the profile layer during thermocompression bonding with the insulating base material, resulting in poor adhesion, and if the variation is so large that it deviates from ±0.5 μm. This is because a residual phenomenon occurs during the etching process when forming the conductor circuit, and the deterioration of the electrical insulation becomes significant.

Since this profile layer is formed by the method described below, it forms a roughened surface and also functions as a thermal deterioration prevention layer. The degree of roughness can be determined by adjusting the electrolytic plating conditions during manufacturing, especially the plating time.
It can be in any state.

This profile layer can be formed by electrolytic plating, especially high speed plating.

That is, a high-speed plating method is applied to the adhesion surface of the copper foil or the copper plating layer electrodeposited on the surface of the conductive base material to the conductive base material to form the profile layer.

The copper foil or the copper plating layer of the conductive base material is used as a cathode, and a Tf. Insoluble anodes such as Pb and Pt-treated Ti are placed facing each other, and a plating bath, which will be described later, is flowed into the gap between these two electrodes so as to be in contact with both electrodes.
Electrolytic copper plating treatment is performed to roughen the cathode surface by depositing copper and at the same time impart thermal deterioration prevention ability.

In this case, the mutual spacing between the anode and the cathode is appropriately set in relation to the contact speed of the plating bath, but is usually 10 to 10 t.
It is preferable that it is about 5m+a.

The electrolytic copper plating bath used is a copper plating bath having the bath composition described above.

Here, CuS04''5H*O is a copper source component, and its concentration in the bath is set to 110 to 130 g//.

When the concentration is less than 1 10 g/l, copper is insufficiently supplied to the cathode surface, making it difficult to form a uniform profile layer with little variation over the entire cathode surface. Further, if the concentration is higher than 130 g//, the roughness becomes large and it becomes difficult to make it uniform. The preferred concentration is 115-120 g/l.

H*SO4 is a component for increasing the ionic conductivity of the plating bath, and its concentration is set at 55 to 65 g/1. If the concentration is less than 5 5 g/l, the overvoltage will be high and roughening will be insufficient, and if it is higher than 65 g/l, the conductivity will be so good that it will not be possible to roughen. The preferred concentration is 55-60
g/1.

NO s- is a component that produces by-products through anodic oxidation, and as a result, deposits Cu on the cathode surface in an uneven manner, contributing to the roughening of the cathode surface, and its concentration is 21 to 2.
4 g/l. If this concentration is lower than 2 1 g/1, there will be a problem that the roughness will be large and its variation will be large, and if it is higher than 24 g/1, the roughness will be too large. This NO x
As a source of ''', for example, nitric acid, KNO
Examples include nitrates such as s, N aN O s.

The Zn compound, Sn compound, or Co compound is a source of Zn, Sn, and Co, respectively, and is a component for improving the thermal deterioration prevention ability of the profile layer together with the chelating agent described later. is 200-1000
ppm. The preferred concentration is 250
~500 ppm.

If this concentration is less than 200 ppm, the thermal deterioration prevention ability of the profile layer will decrease, and 1
If it is higher than 000 ppm, the mechanical strength of the profile layer decreases, causing problems such as the profile layer falling off during handling, which is disadvantageous.

The Zn compound may be any compound that can be dissolved in the plating bath, such as ZnO, ZnSO, etc.
I can give you s. In addition, as Sn compounds,
SnCl! ．． Examples of Co compounds include SnO, SnS 04, and the like.
Co(NOs)z, COC1g * COSO4 can be given.

The concentration of the chelating agent is set at 5-20 g/l. If this concentration is lower than 5 g/1, a uniform thermal deterioration prevention layer cannot be formed, and no improvement in the thermal deterioration prevention ability of the profile layer is observed. In addition, due to the solubility in the plating bath,
The upper limit is 20 g/l. The preferred concentration is 5-1
It is 0 g/1.

Examples of this chelating agent include ethylenediaminetetraacetic acid (EDTA), tartaric acid, ethylenediamine, and pyrophosphoric acid, but among these, when EDTA is used, it has a greater ability to prevent thermal deterioration. suitable.

The plating bath prepared in this way has a pH of l~
When used, it is preferable to set the flow so that the Reynolds number (Re) exceeds 2300 to create a turbulent state. When Re is less than 2300, a laminar flow state occurs, which is not preferable.

This plating bath is passed through at high speed so as to contact the surfaces of the anode and cathode. At this time, the contact speed with the cathode surface (therefore, the anode surface) is 0.3~0. 7 m/s
Managed by ec. If the contact speed is less than 0.3 m/sec, the supply speed of Cu ions to the cathode surface will be slow, resulting in large variations in the protrusion height in the profile layer, and the formed profile layer will be non-uniform. The liquid contact speed is 0. If it is larger than 7 m/see, the roughness of the profile layer formed will be insufficient, which is disadvantageous. The preferred liquid contact speed is 0.35 to 0.
．． 45 m/see.

Further, the current density is controlled to be 30 to 55 A/drrr. If the current density is less than 3OA/drrr, the plating layer will not be baked uniformly, and problems will occur such as large variations in the protrusion height in the profile layer.
This is because if it exceeds A/dnf, problems such as excessive burning and an excessively large protrusion height of the profile layer will occur.

At this time, the bath temperature of the plating bath is preferably 20 to 22°C. If the bath temperature is less than 20°C, the movement speed of Cu ions will be slow, making it easier to form a polarized layer on the cathode surface.
This is because, as a result, the formation speed of the profile layer decreases. Furthermore, if the bath temperature exceeds 22° C., the roughness will not increase unless the current density is increased, which is uneconomical.

By appropriately selecting these electrolytic plating conditions and particularly adjusting the plating time, a profile layer having a protrusion height of an arbitrary height is formed, and the desired copper foil layer is manufactured.

In addition, in the present invention, the above-mentioned plating treatment may be performed in one step, or may be performed as a continuous two-step process within the range of the above-mentioned plating conditions.

(Example of the invention) (1) Setting up the plating bath Various types of plating baths were constructed using the combinations shown in Table 1.

(2) Profile layer shape or hardened stainless steel (SUS)
One side of the 630) veneer was polished to a surface roughness of 0.0 by using a rotary cloth polisher with oscillation. Surface treatment was performed so that the thickness was 8 μm, and then HzS 04
A Cu plating layer with a thickness of 5 μm was formed using a 180 g/l CuSO*●5HtO plating bath.

This single plate with a Cu plating layer is used as a cathode, and the Ti plate is used as an anode.
Electrolytic plating was carried out under the conditions shown in Table 1 with an interelectrode distance of 14 to 15 mm.

In addition, in the display of plating conditions in Table 1, for example, in the case of Example 3, first, the liquid contact speed is 0. 7 m/s
plating for 15 seconds at a current density of 53 A/drri, followed by a wetting speed of 0. 3 m
This shows a two-step process in which plating is performed for 6 seconds under the conditions of /see and current density of 30 A/drd. The same applies to Comparative Examples 13, 14, and 15.

The surface of each copper plating layer obtained was observed with a scanning electron microscope, and the average value (μm) and variation in the protrusion height of the profiled layer were calculated. The results are summarized in the first
Shown in the table.

(3) Performance of profile layer The copper foil layer manufactured by each method shown in Table 1 was prepared with a thickness of 0.
Layered on a 1 m glass epoxy FR-4 prepreg, the whole was heated at a temperature of 25°C and a press pressure of 170 kg/cI.
1, and then only the stainless steel veneer was peeled off to obtain a copper-clad laminate.

For each copper-clad laminate, the adhesion strength between the copper foil layer and the brev leg, the residual copper status after etching, and the ability to prevent thermal deterioration were investigated using the following specifications.

Adhesion strength: Make a notch in the copper foil layer of each copper clad laminate to a width of 1
A short fence-shaped test piece of 0 mm was used, and one end of the test piece was peeled off to an appropriate length, which was held with a support metal fitting, and the test piece was peeled off at a speed of 50 M/min in a direction perpendicular to the copper foil layer. Measured as the beering value (kg/cm).

The larger this value, the better the adhesion. It means that there is.

Residual copper status after etching: An evaluation circuit with a 100 μm pattern (gap of 200 μm) was created from each copper-clad laminate based on the usual manufacturing method of printed circuit boards, and a voltage of 500 VDC was applied to the circuit, causing a spark. We observed the occurrence of resistance, decrease in resistance value, and instability. The case where the resistance value at this time was 10'MΩ or more and there was no instability was shown as ○, and the case where sparks were generated or the resistance value was less than 10'MΩ and unstable was shown as ×.

Thermal deterioration prevention ability: Each copper-clad laminate was left in an oven at 180° C. for 48 hours and then taken out, and the peeling strength at that time was measured.

The larger this value is, the higher the thermal deterioration resistance. Indicates excellent stopping power.

The above results are collectively shown in Table I.

(Margin below) (Effects of the invention) As is clear from the above explanation, the copper foil layer for copper-clad laminates of the present invention has good adhesion to the insulating base material despite the low protrusion height of the profile layer. Since the strength is high and the variation in protrusion height is small, there is little loss of remaining foot during etching. Moreover, it has excellent ability to prevent thermal deterioration. These effects can be achieved by using a plating bath with the composition specified in the present invention.
Moreover, this is based on the fact that the profile layer is formed under the plating conditions of the present invention.

Since the formation of this profile layer is performed by applying a high-speed plating method, it has high productivity, but above all, conventionally, the shape of the roughened surface or the shape of the thermal deterioration prevention layer has not been improved. This is a fundamental improvement over the previous method of successively combining independent processes, and by using a new electrolytic copper plating bath, it is now possible to perform both roughening and thermal deterioration prevention treatment in one process. , its industrial value is extremely large.

Claims (4)

[Claims] (1) The roughness of the adhesive surface with the insulating base material is 7 μm or less, and the variation in roughness is ±0.5 μm from the average roughness.
A copper foil layer for a copper-clad laminate, characterized in that the copper foil layer is within (2) The copper foil layer for a copper-clad laminate according to claim 1, wherein the copper foil layer is a copper plating layer formed on the surface of a conductive base material. (3) A copper plating bath containing at least one metal selected from the group of zinc, tin, and cobalt is applied to the surface of the copper plating layer formed on the surface of the copper foil or the conductive base material.
While contacting the liquid at a contact speed of 3 to 0.7 m/sec,
A method for producing a copper foil layer for a copper-clad laminate, comprising performing plating at a current density of 0 to 55 A/dm^2 to form a roughened surface having a thermal deterioration prevention layer. (4) The bath composition of the plating bath according to claim 3 is copper sulfate pentahydrate 1
10-130 g/l, sulfuric acid 55-65 g/l, nitrate ions 21-24 g/l, at least one compound selected from the group of zinc compounds, tin compounds or cobalt compounds 200-1000 ppm, chelating agent 5-20 g/l An electrolytic copper plating bath characterized by: