JP3452674B2 - Manufacturing method of high rigidity copper clad laminate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated board on which electronic parts are mounted, the circuit processing step, the parts mounting step and the finished product having a small deflection and a warp, and the laminated board having a small thermal expansion coefficient. The present invention relates to a laminated plate having a highly reliable solder joint part.

[0002]

2. Description of the Related Art In recent years, printed wiring boards have been used in an extremely wide range of applications, and the characteristics required for laminated boards constituting these printed wiring boards have become more diverse. Under these circumstances, the demand for thinner printed wiring boards is increasing as electronic devices become smaller and lighter. However, thinning the printed wiring board lowers the bending rigidity of the printed wiring board, which tends to cause large dimensional changes and warpage in the circuit processing process, which tends to reduce dimensional accuracy. However, there is a problem that the deflection that occurs at the time of the solder leveler is large, and the mounting accuracy of components is likely to decrease. In order to solve these problems, various methods for increasing the rigidity of thin laminated plates have been proposed so far.

In place of the E glass fiber which is usually used for a laminated board for a printed wiring board, a method of using S glass fiber, aramid fiber or carbon fiber having a higher elastic modulus in a woven cloth, and a resin of the laminated board are used. A method of adding various fillers and a method of reducing the compounding ratio of the epoxy resin with which the glass cloth base material is impregnated have been proposed as a method for improving the rigidity of the laminate.

[0004]

However, S glass fiber has only 16% higher elastic modulus than E glass fiber,
The rigidity of the laminated plate cannot be improved significantly. Further, the laminated sheet using the aramid fiber woven fabric has improved rigidity, but is largely inferior in machinability and moisture and heat resistance. Since a laminated board using a carbon fiber woven cloth is electrically conductive, it is difficult to use as an insulating substrate. The method of decreasing the compounding ratio of the epoxy resin with which the glass cloth base material is impregnated, in other words, the method of increasing the volume fraction of the glass cloth in the laminated plate exhibits an effect of improving the rigidity by about 30%. Further, by combining with S glass cloth, higher rigidity can be achieved. However, a copper-clad laminate produced by using a prepreg having such a high volume fraction of glass cloth is inferior in electrolytic corrosion resistance, so that a short circuit between circuits due to migration of copper ions is likely to occur. The cause is that the copper foil and the glass fiber come into contact with each other by increasing the volume fraction of the glass cloth. Since copper ions move along the glass fibers, a printed wiring board in which the copper foil and the glass fibers are in contact is likely to cause a short circuit between circuits due to migration of copper ions. Further, since the copper foil and the fiber are in direct contact with each other, there is a problem that the adhesive strength of the copper foil is lowered.

The method of blending the filler in the resin of the laminated board can lower the resin volume fraction of the laminated board more than the method of increasing the volume fraction of the glass cloth described above. By increasing the volume fraction of the material, it is possible to improve the rigidity by 30% or more. However, a copper-clad laminate produced by using a prepreg in which such a filler is mixed to have a high volume fraction is likely to cause a short circuit between circuits due to migration of copper ions and has poor electrolytic corrosion resistance. The cause is that the copper foil comes into contact with the filler by increasing the volume fraction of the filler. Since copper ions move along the interface between the filler and the resin, the copper foil comes into contact with the filler and the fillers. A printed wiring board containing a filler in a high volume fraction is apt to cause a short circuit between circuits due to migration of copper ions. Furthermore, since the copper foil and the filler are in direct contact with each other, there arises a problem that the adhesive strength of the copper foil is lowered.

It is an object of the present invention to provide a method for producing a copper clad laminate excellent in rigidity and low thermal expansion without impairing other properties such as electrolytic corrosion resistance and copper foil adhesion.

[0007]

That is, the method for producing a copper-clad laminate of the present invention comprises a prepreg obtained by impregnating and drying a glass cloth with a thermosetting resin composition containing 20 to 60% by volume of a filler. Or, a plurality of copper foils are laminated, and a copper foil having an adhesive layer having a thickness of 1 to 5 μm formed on at least one surface thereof in contact with the prepreg is superposed and integrally thermoformed.

The filler used in the present invention is not particularly limited as long as it is used for ordinary resins and has a higher elastic modulus than the resin. Examples of fillers include magnesium hydroxide, talc, alumina, magnesia, E
Powdered fillers such as glass, silica, titanium dioxide, potassium titanate, calcium silicate, aluminum silicate, calcium carbonate, clay, silicon nitride, silicon carbide, aluminum borate, and synthetic mica, and glass, asbestos, Short fiber filler such as rock wool and aramid,
Examples thereof include whiskers such as silicon carbide, alumina and aluminum borate. The filler is mixed with the resin so that the volume fraction of the filler in the resin containing the filler is 20 to 60%. This is because when the filler volume fraction is 20% or less, the effect of increasing the rigidity of the laminated plate is small, and when it is 60% or more, voids are generated in the laminated plate after molding.

As the glass cloth used in the present invention,
E glass fiber or silica commonly used,
A glass cloth made of so-called S glass fiber whose alumina and magnesia contents are 60% by weight or more, 20% by weight or more and 15% by weight or less, respectively, and the sum of these three components is 97% by weight or more is used. Preferably. As the weaving method of the glass cloth, the plain weave used in the general glass cloth for printed wiring boards is preferable,
Further, a plain weave cloth and a satin weave cloth having a particularly long interlacing interval of fibers are more preferable because they have a high limit of the glass volume fraction that does not cause a blur due to a shortage of the absolute amount of the resin.

The resin used in the present invention is not particularly limited as long as it is an ordinary thermosetting resin, that is, a resin that can be crosslinked between molecules by light, radiation or heating to give an insoluble and infusible cured product. Examples thereof include phenol resins, melamine resins, epoxy resins, silicon resins, unsaturated polyester resins, cyanate ester resins, isocyanate resins, polyimide resins and various modified resins thereof. Of these, epoxy resin and polyimide resin are particularly preferable in view of the characteristics of the laminated plate.

The total volume fraction of glass and filler in the prepreg of the present invention is preferably 55% or more. This is because if the volume fraction is 55% or more, a particularly large effect of improving rigidity can be obtained. further,
It is preferable that the total volume fraction of the glass and the filler is as high as possible within a range in which blur due to insufficient absolute amount of resin does not occur. The total volume fraction of the glass and the filler, which is the limit where no blur occurs, is about 60% for a general glass cloth for printed wiring boards, but it varies depending on the fiber diameter of the glass cloth, the number of strands, and the weaving method. It is desirable to obtain in advance by experiments.

In the present invention, the adhesive layer formed between the glass cloth and the composite material layer made of resin and the adhesive layer formed on the copper foil are electrically insulating resins. A thermosetting resin such as a phenol resin, an epoxy resin or a butyral resin or a thermoplastic resin is used alone or in a mixture. If the thickness of the adhesive layer is less than 1 μm, the effect of improving electrolytic corrosion resistance and adhesion with the copper foil is small, and if it is 5 μm or more, the effect of improving rigidity is small. Therefore, in the present invention, the thickness of the adhesive layer is 1 to 5 μm.

[0013]

The copper-clad laminate obtained as described above contains 20 to 60% by volume of the filler in the resin, and the rigidity can be greatly improved as compared with the ordinary copper-clad laminate. Moreover, since the adhesive layer having a thickness of 1 to 5 μm is provided between the composite material layer and the copper foil, it is possible to prevent the contact between the filler and the copper foil, which is likely to occur in the copper clad laminate containing a large amount of the filler. As a result, electrolytic corrosion resistance and copper foil adhesiveness are not impaired. Further, since the resin volume fraction is low, the coefficient of thermal expansion is low. As a result, dimensional changes and warpage are small in the printed wiring board processing process, dimensional accuracy is improved, and connection reliability with mounted components after component mounting can also be improved. . Furthermore, by setting the total volume fraction of the glass cloth and the filler in the prepreg to be 55% or more,
The effects described above can be further enhanced.

[0014]

EXAMPLES The present invention will now be described in detail based on examples, but the present invention is not limited thereto. A plain weave glass cloth made of E glass fiber having a mass per unit area of 48 g / m ² is impregnated with an epoxy resin varnish containing 50% by volume of aluminum hydroxide and dried to fill the glass with a volume fraction of 40%. A prepreg having a volume fraction of 30% was produced. On the other hand, an adhesive layer having a thickness of 2 μm and containing butyral resin as a main component was formed on the roughened surface of the electrolytic copper foil having a thickness of 18 μm. Two pieces of the prepreg are laminated, and the copper foil with the adhesive layer is formed so that the adhesive layers contact the prepreg above and below, and they are integrated by thermocompression molding by pressing, and the thickness excluding the copper foil is 100 μm. A copper clad laminate was obtained. Copper foil peeling strength of this copper clad laminate, coefficient of thermal expansion,
Table 1 shows the measurement results of the flexural modulus and the electrolytic corrosion test results. The thermal expansion coefficient is TMA after removing the copper foil by etching.
The surface direction (the average of the warp yarn direction and the weft yarn direction) was measured by the method, and the bending elastic modulus was measured from three-point bending after removing the copper foil by etching. Electrolytic corrosion test board is line /
A conductor pattern having a space of 100 μm / 100 μm is formed from the copper foil of the copper-clad laminate, and an insulating layer made of an epoxy adhesive film is formed on the copper foil. Under environmental conditions of RH, DC15V was applied for 1000 hours between the conductor lines. The copper foil peeling strength was 2.1 kgf / cm, and the thermal expansion coefficient was 8.5 ppm / ° C. (plane direction). In the electrolytic corrosion test, defects such as short circuit did not occur, and the insulation resistance between the lines after the test for 1000 hours was 10 12 or more. The flexural modulus was 27 GPa.

Next, a comparative example for confirming the effects of these examples will be shown.

Comparative Example 1 The mass per unit area is 48 g / m ^2. Epoxy resin varnish was impregnated into a plain weave glass cloth made of E glass fiber of No. 1 and dried to prepare a prepreg having a glass volume fraction of 38%. The above-mentioned two prepregs are laminated, and a single-sided roughened electrolytic copper foil having a thickness of 18 μm is constructed so that the roughened surfaces are in contact with the prepregs above and below, and they are integrated by thermocompression molding with a press, and the thickness excluding the copper foil. Is 100 μm, and the glass volume fraction in the composite of glass cloth and resin is 38.
% Copper-clad laminate was obtained. Table 1 shows the measurement results of the copper foil peeling strength, the coefficient of thermal expansion, and the flexural modulus of the copper-clad laminate, and the electrolytic corrosion test results. The measurement and test conditions are the same as in the example. Copper foil peeling strength is 2.1kgf / cm
And the coefficient of thermal expansion was 15.5 ppm / ° C. (plane direction). In the electrolytic corrosion test, defects such as a short circuit did not occur, and the insulation resistance between lines after the test for 1000 hours was 10 12 or more, but the flexural modulus was 15 GPa.

Comparative Example 2 The mass per unit area is 48 g / m ^2. A plain weave glass cloth made of E glass fiber with 5 parts aluminum hydroxide
Impregnated with 0% by volume of epoxy resin varnish and dried to give a glass volume fraction of 38% and a filler volume fraction of 31%.
Was prepared. Two sheets of the prepreg are laminated, and the roughened surfaces are in contact with the prepreg above and below the prepreg.
A single-sided roughened electrolytic copper foil having a thickness of 18 μm is formed, and thermocompressed by a press to be integrated, and the thickness excluding the copper foil is 100 μm.
A copper clad laminate was obtained. Table 1 shows the measurement results of the copper foil peeling strength, the coefficient of thermal expansion, and the flexural modulus of the copper-clad laminate, and the electrolytic corrosion test results. The measurement and test conditions are the same as in Example 1. The copper foil peeling strength was 1.2 kgf / cm, and the thermal expansion coefficient was 8.5 ppm / ° C. (plane direction). The flexural modulus was 28 GPa, but in the electrolytic corrosion test, a short circuit occurred between the lines after 30 hours.

As shown in the examples, since the copper clad laminate obtained by the present invention contains a large amount of filler, the glass volume fraction as shown in Comparative Example 1 is about 40%. Rigidity can be significantly improved compared to a normal copper clad laminate. Moreover, between the composite material layer and the copper foil is 1 to 5 μm.
Since the adhesive layer of No. 1 is provided, it is possible to prevent the contact between the filler and the copper foil, which is generated in the copper-clad laminate having only a large amount of the conventional filler as shown in Comparative Example 2, as a result. There is no loss of corrosion and copper foil adhesion. Further, as the resin volume fraction is low, the coefficient of thermal expansion is low. As a result, dimensional change and warpage in the printed wiring board processing step are small, dimensional accuracy is improved, and connection reliability with mounted components after component mounting can be improved.

[0019]

[Table 1]

[0020]

The copper-clad laminate of the present invention achieves a significant improvement in rigidity as compared with the conventional copper-clad laminate without impairing other characteristics such as electrolytic corrosion resistance and copper foil adhesion. is there.
Furthermore, since the coefficient of thermal expansion is low, dimensional changes and warpage in the printed wiring board processing step are small, dimensional accuracy is improved, and connection reliability with mounted components after component mounting is excellent.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-61-270151 (JP, A) JP-A-57-197892 (JP, A) JP-A-56-40296 (JP, A) JP-A-5- 309789 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 H05K 3/00 H05K 1/03

Claims (4)

(57) [Claims] 1. A single or a plurality of prepregs obtained by impregnating and drying a glass cloth with a thermosetting resin composition containing 20 to 60% by volume of a filler are laminated, and at least one surface of the prepreg is in contact with the prepreg. In addition, a copper foil having an adhesive layer having a thickness of 1 to 5 μm for preventing the contact between the filler and the copper foil is superposed and thermocompression-molded integrally, Production method. 2. The method for producing a copper clad laminate according to claim 1, wherein the total volume content of the glass cloth and the filler in the prepreg is 55% or more. 3. A glass cloth with a thermosetting resin and 20 to 20 parts.
Copper is provided on at least one surface of a prepreg impregnated with a thermosetting resin composition containing 60% by volume of a filler via an adhesive layer having a thickness of 5 μm or less for preventing contact between the filler and the copper foil. A copper clad laminate in which foils are laminated. 4. The copper clad laminate according to claim 3, wherein the total volume content of the glass cloth and the filler in the prepreg is 55% or more.