JP2917645B2 - Manufacturing method of 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 method for producing a copper-clad laminate used for a printed wiring board.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller and higher in density, electronic components used have been shifting from conventional leaded components to chip components. The mounting method is becoming mainstream. Accordingly, various requirements for a copper-clad laminate used as a printed wiring board have become strict. In other words, when chip components are surface-mounted on a printed wiring board,
From the viewpoint of connection reliability, matching of the thermal expansion coefficient becomes a problem. However, the thermal expansion coefficient of a fiber-reinforced plastic substrate such as a glass cloth base epoxy resin copper-clad laminate generally widely used as a printed wiring board is considerably larger than that of a chip component. Therefore, when chip components are surface-mounted, it is not possible to secure connection reliability that can withstand practical use. In order to improve the connection reliability with chip components, a substrate with a coefficient of thermal expansion closer to that of chip components,
That is, a substrate having a low coefficient of thermal expansion is required.

[0003]

As the substrate material having a low coefficient of thermal expansion, a ceramic substrate different from the above-mentioned organic substrate such as alumina or aluminum nitride, or a low thermal expansion metal such as Invar or 42 alloy is used as a core. Used metal core substrate. However, looking at these, the ceramic substrate is so hard that it cannot be machined, such as drilling or cutting, like organic substrates.
There are drawbacks such as the inability to form a large-sized substrate, complicated circuit processing and multi-layering steps, and increased costs. Further, a metal core substrate having a low-thermal-expansion metal as a core has disadvantages such as being heavy and unable to be reduced in weight, and having to cover the inside of the metal core with an insulating coating when forming a through hole. Therefore, development of a conventional organic substrate having a low coefficient of thermal expansion is desired. As an organic substrate having a low thermal expansion, a substrate using a low thermal expansion base material such as an aromatic polyamide fiber or a quartz fiber has been developed, but it has not been put into practical use due to difficulty in machinability.

On the other hand, the present inventors have considered that such a demand can be met by compounding a ceramic and an organic substrate, and have considered that copper foil and an organic substrate such as a glass cloth base epoxy resin can be used. We developed a substrate having a ceramic thermal sprayed layer, already disclosed (JP 62-152742 official <br/> paper) to. Due to the presence of a ceramic layer with a low coefficient of thermal expansion, this substrate has a lower in-plane coefficient of thermal expansion than conventional organic substrates such as glass-cloth-based epoxy resin laminates, and the reliability of connection with chip components to be mounted is low. It is effective for improving the performance. However, recently, chip components have been further reduced in thickness and density, and the thermal expansion coefficient of chip components tends to be lower. For this reason, the demand for lower thermal expansion of the substrate is becoming more severe. Therefore, there is an increasing demand for lower thermal expansion of the above-mentioned substrates. To meet such demands, even if the ceramic layer formed by spraying as described above and a laminated board such as a conventional glass cloth substrate epoxy resin are combined, the thermal expansion coefficient of the conventional glass cloth It has been found that the coefficient of thermal expansion of the entire substrate is limited by the presence of the ceramic layer because it is so high as compared with that of the component.

The present invention solves the above-mentioned problems, and can handle the same as a conventional copper-clad laminate based on an organic substrate, and has a sufficiently low coefficient of thermal expansion. In this case, a method of manufacturing a copper-clad laminate excellent in connection reliability is provided.

[0006]

SUMMARY OF THE INVENTION The present invention provides a copper-clad laminate formed by thermally spraying ceramic on one side of a copper foil to form a ceramic layer, laminating a prepreg so as to be in contact with the ceramic layer, and hot pressing. in the method of manufacturing, SiO ₂ Te <br/> and the prepreg, Al ₂ O ₃ and MgO content, respectively,
20% by weight or more of an inorganic filler is contained in a glass fiber base material of 60% by weight or more, 20% by weight or more and 15% by weight or less, and the total of these three components is 97% by weight or more.
Impregnated and dried thermosetting resin varnish
It is characterized by that .

The ceramic layer is formed by spraying the ceramic layer on one side of the copper foil by plasma spraying or gas spraying. The ceramic to be sprayed is alumina, titania,
Electrically insulating ceramics such as zirconia, magnesia, mullite, spinel, cordierite, steatite, forsterite, and aluminum titanate can be used. It is suitable. Cordierite has relatively low hardness among ceramics, and has the advantage of not impairing the machinability, such as drilling, of a substrate. The thickness of the ceramic layer formed by thermal spraying does not limit the scope of the present invention, but is preferably in the range of 25 to 300 μm. If the thickness of the thermal sprayed ceramic layer is small, the effect on lowering the thermal expansion of the substrate is not sufficient, so the effect on the improvement of the connection reliability with the chip component is reduced. That's why.

Further, glass fiber is used as the fiber of the prepreg, and its components are SiO ₂ , Al ₂ O ₃ , and MgO whose contents are 60% by weight or more, 20% by weight or more and 15% by weight or less, respectively. The reason why the total of the three components is specified to be 97% by weight or more is that the glass fiber of the component in this range has a lower coefficient of thermal expansion than other glass fibers and is excellent in machinability. That is, when the content of SiO ₂ is less than 60% by weight, when the content of Al ₂ O ₃ is less than 20% by weight, or when the content of MgO exceeds 15% by weight, Since the expansion coefficient does not become sufficiently low, the effect of reducing the thermal expansion of the substrate is reduced. The glass fiber is made of SiO ₂ or Al ₂ O.
_{In the} case of one component of _3, the coefficient of thermal expansion is low,
When used for a substrate due to poor workability, mechanical workability such as drill workability is significantly impaired. Therefore, by using the glass fiber having the component of the present invention, it is possible to achieve both low thermal expansion of the substrate and retention of machinability. As glass fibers having such a composition, for example, S glass having a SiO ₂ content of 64.3% by weight, an Al ₂ O ₃ content of 24.8% by weight, and a MgO content of 10.3% by weight Fibers (or T-glass fibers) are commercially available and can be suitably used. The thermal expansion coefficient of this glass fiber is 2.4 × 10 ⁻⁶ / ° C. The thermal expansion coefficient of E glass fiber, which is widely used in general copper-clad laminates, is 4.5 × 10 ^-6 / ° C.
The respective contents of O ₂ , Al ₂ O ₃ , and MgO are, for example, 54.3% by weight, 15% by weight, and 4.7% by weight.

Next, the inorganic filler mixed with the thermosetting resin varnish impregnated into the glass fiber will be described.
As an inorganic filler, silica, alumina, titania, zirconia, magnesia, calcium carbonate, aluminum hydroxide, mullite, which are widely used for various applications,
Ceramic or glass powders such as spinel, cordierite, zircon, and calcia, whiskers such as potassium titanate, aluminum borate, silicon carbide, silicon nitride, and alumina, and short fibers such as glass fibers and silica fibers can be used. Among these, it is preferable to use fused silica which has a relatively low coefficient of thermal expansion of about 0.5 × 10 ⁻⁶ / ° C. and is inexpensive and easily available. The mixing amount of the thermosetting resin varnish is 2% in the varnish.
The content should be 0% by weight or more. If the content is less than 20% by weight, the effect of lowering the thermal expansion coefficient of the substrate is small.

As the thermosetting resin, epoxy resin, polyimide resin, phenol resin, vinyl ester resin,
A silicone resin, a melamine resin, an unsaturated polyester resin, or the like is used, and an epoxy resin or a polyimide resin widely used as a copper-clad laminate is suitable.

[0011]

The ceramic layer formed on the copper foil by thermal spraying adheres firmly to the resin of the prepreg at the time of hot pressing with the prepreg, and is integrated. The in-plane coefficient of thermal expansion of the substrate obtained by combining the ceramic layer and the organic substrate obtained in this manner can be calculated from the following equation 1 according to the composite rule, and the measured values are almost the same.

[0012]

[Equation 1] _{α = (E C V C α} C + E M V M α M) / (E C V C + E M V M) α: thermal expansion coefficient of the composite alpha _C: thermal expansion coefficient of the ceramic layer alpha _M : thermal expansion coefficient of the organic substrate E _C: elastic modulus of the ceramic layer E _M: elastic modulus of the organic substrate V _C: volume fraction of the ceramic layer V _M: the volume fraction of the organic substrate

As is apparent from the above equation, the thermal expansion coefficient of the ceramic layer is lower than that of the organic substrate, and the thermal expansion coefficient of the substrate obtained by combining them is lower than that of the organic substrate. In view of the above equation, it is effective to lower the thermal expansion coefficient of the organic substrate in order to further lower the thermal expansion coefficient of the substrate.

To lower the coefficient of thermal expansion of an organic substrate,
It is necessary to lower the thermal expansion coefficient of the resin and the fiber base material as the constituent components. First, regarding the fiber base material, as the fiber base material having a lower coefficient of thermal expansion than the E glass fiber used for the ordinary laminate, SiO ₂ in addition to the component range used in the present invention, for example, S glass fiber, is used. Examples thereof include quartz glass fiber whose main component is alumina, alumina fiber whose main component is Al ₂ O ₃ , and aromatic polyamide fiber. By using these low thermal expansion base materials, the thermal expansion coefficient of the organic substrate can be reduced. However, among these, quartz glass and alumina fibers are very hard, and therefore have extremely poor workability and are difficult to put into practical use. Further, aromatic polyamide fibers have drawbacks such as poor affinity for resins and poor workability, and have not been widely used. Thus, the glass fiber having the component ratio of the present invention is optimal from the viewpoint of achieving both workability and a low coefficient of thermal expansion.

Further, when an inorganic filler is mixed with the thermosetting resin of the prepreg, the thermal expansion coefficient of the organic substrate can be further reduced. The coefficient of thermal expansion of the organic substrate is determined by the content of the fiber and resin that are its constituent components, the higher the content of the fiber having a lower coefficient of thermal expansion, the lower the content of the resin having a higher coefficient of thermal expansion, Lower. Further, when the coefficient of thermal expansion of the resin decreases, the coefficient of thermal expansion of the substrate also decreases.
Therefore, if an inorganic filler having a significantly lower coefficient of thermal expansion than the resin is mixed with the resin, the coefficient of thermal expansion of the resin system becomes lower. Therefore, by using a resin mixed with an inorganic filler, the coefficient of thermal expansion of the organic substrate can be further reduced.

As described above, in the organic substrate, a ceramic layer formed by thermal spraying is provided on the surface, and a prepreg obtained by impregnating a glass fiber made of a specific component with a resin mixed with an inorganic filler is used. Accordingly, the coefficient of thermal expansion in the plane of the substrate can be made lower than ever before. Further, the substrate obtained in this manner is porous since the ceramic layer is formed by thermal spraying, and is therefore superior in machinability as compared with a sintered body. Further, the fiber base material also has good machinability, unlike quartz glass fibers and aromatic polyamide fibers which have been conventionally studied as low thermal expansion base materials. Therefore, it is possible to process the printed wiring board in the same process as that of the conventional glass cloth base epoxy resin laminate or the like.

[0017]

Next, embodiments of the present invention will be described. Example 1 Cordierite was sprayed on a roughened surface of electrolytic copper foil by a plasma spraying machine to form a cordierite layer having a thickness of 100 μm, and a copper foil having a cordierite layer on one side was obtained. Next, 64.3% by weight of SiO ₂ and 24.3% of Al ₂ O ₃ .
An S glass fiber cloth (manufactured by Nitto Bo) containing 8% by weight and 10.3% by weight of MgO was impregnated with an epoxy resin varnish and dried to obtain a prepreg having a resin content of 42% by weight. A six-layer plate (with a thickness of 1.2 m) having the structure shown in FIG.
m) was prepared. As a result of measuring the in-plane thermal expansion coefficient of this six-layer plate, it was 8.2 × 10 ⁻⁶ / ° C. In the figure,
1 is a copper foil, 2 is a cordierite layer, and 3 is a prepreg.

Example 2 A glass fiber content was prepared in the same manner as in Example 1 except that an epoxy resin varnish was prepared by mixing and stirring and uniformly dispersing 50% by weight of a fused silica powder at a solid content ratio. 5
8% by weight of prepreg was obtained. Using this prepreg and a copper foil having the same ceramic layer as in Example 1, a six-layer plate (plate thickness 1.2 mm) having the configuration shown in FIG. 2 was produced. This 6
When the in-plane coefficient of thermal expansion of the layer plate was measured, it was found that 6.2 × 1
0 ^-6 / ° C. In the figure, 1 is a copper foil, 2 is a cordierite layer and 3 is a prepreg.

Comparative Example For comparison with the example, an E glass fiber cloth (54.3% by weight of SiO ₂ , Al ₂ O ₃ 15.0% by weight, 4.7% by weight of MgO and 23.0% by weight of CaO
(Comparative Example 1), a prepreg using the same S glass fiber cloth as in the example (Comparative Example 2), and a copper foil provided with a ceramic layer as in the example. A prepreg using an E glass fiber cloth without an inorganic filler (Comparative Example 3) and a thermosetting resin varnish mixed with a fused silica powder as in Example 2 using a copper foil without a ceramic layer For a prepreg using Comparative Example 4 and S glass fiber cloth (Comparative Example 4), a 6-layer plate having a thickness of 1.2 mm was produced, and the in-plane thermal expansion coefficient was measured. The results are shown in Table 1 in comparison with the examples.

[0020]

[Table 1]

From Table 1, it is clear that the six-layer plate of the example has a lower coefficient of thermal expansion than the six-layer plate of the comparative example.

[0022]

According to the present invention, a copper-clad laminate that can be handled in the same manner as a conventional copper-clad laminate, has a low coefficient of thermal expansion, and has excellent connection reliability with chip components can be easily obtained. It can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a laminated structure of a copper-clad laminate in an example of the present invention.

FIG. 2 is a schematic diagram showing a laminated configuration of a copper-clad laminate in an example of the present invention.

[Explanation of symbols]

 1 Copper foil 2 Cordierite layer 3 Prepreg

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenji Tsukanishi 1500 Ogawa Oji, Shimodate City, Ibaraki Pref. Hitachi Chemical Co., Ltd. Shimodate Plant (56) Reference JP-A-2-253940 62-56679 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B32B 15/04 B32B 17/04 H05K 3/38

Claims (2)

(57) [Claims] 1. A method for producing a copper-clad laminate, wherein a ceramic layer is formed by spraying ceramic on one side of a copper foil, a prepreg is laminated so as to be in contact with the ceramic layer, and hot-pressed. The content of SiO ₂ , Al ₂ O _3, and MgO is 60% by weight or more, 20% by weight or more and 15% by weight or less, and the total of these three components is 97% by weight or more. , Mineral charge
A method for producing a copper-clad laminate, characterized by using a product obtained by impregnating and drying a thermosetting resin varnish containing 20% by weight or more of a filler . 2. The method according to claim 1, wherein the ceramic of the ceramic layer is cordiera.
The method for producing a copper-clad laminate according to claim 1, wherein the method mainly comprises a site .