JPH02293132A - Thermoplastic resin laminated sheet - Google Patents

Abstract

PURPOSE:To enhance the close adhesiveness and peel strength of a ceramic layer and a base material layer by filling the gap parts of a ceramic layer with a thermoplastic resin before integrating a thermoplastic resin impregnated base layer with said ceramic layer. CONSTITUTION:A ceramic layer 2 is formed to the single surface of a metal foil (copper foil) 1 and the gap parts of said ceramic layer are filled with a thermoplastic resin (FEP resin) 3. Subsequently, a thermoplastic resin (PTEF resin) impregnated base material layer 4 is provided to the surface of the ceramic layer 2 and both layers 2, 4 are integrated to obtain a desired laminated sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industry> Second Field of Application> The present invention relates to a thermoplastic resin laminate having a ceramic layer between a metal foil and a thermoplastic resin-impregnated base material layer.

《Prior Technology》 Until now, printed wiring boards have been made by impregnating a fiber base material such as paper, glass fiber, or Kevlar fiber with thermosetting resin such as phenol resin, epoxy resin, or polyimide resin, and then coating the surface with metal such as copper foil. Foil-covered laminates have been widely used.

However, recently, a laminate in which the fiber base H is impregnated with a thermoplastic resin has been attracting attention instead of the conventional laminate mainly composed of a thermosetting resin. This is because laminates using these thermoplastic resins have the following features.

That is, thermoplastic resins such as Teflon resin have a smaller dielectric constant and dielectric loss tangent than thermosetting resins such as phenol resin, epoxy resin, and polyimide resin. In a printed wiring board, the signal transmission speed and transmission loss of the circuit are greatly influenced by the dielectric constant and dielectric loss tangent of the board. The smaller the dielectric constant of the substrate, the higher the signal transmission speed, and the smaller the dielectric loss tangent, the smaller the transmission loss.

Therefore, in applications such as computers that require advanced signal transmission and high efficiency, the substrate is required to have a low dielectric constant and a low dielectric loss tangent. For these reasons, thermoplastic resin substrates with low dielectric constants and low dielectric loss tangents are attracting attention.

However, even thermoplastic resin laminates having such features have the following problems.

The reason is that it has a large coefficient of thermal expansion. The coefficient of thermal expansion in the plane direction of glass cloth-based thermoplastic resin laminates such as Teflon resin is 20 to 25 x 10-6/℃, and that of glass cloth-based thermosetting resin laminates such as epoxy resin and polyimide resin is 10 to 25 This is larger than 15×10-6/°C. This results in a decrease in connection reliability with components connected on the board. That is, a silicon chip (coefficient of thermal expansion 3.5 x 10-6/℃), an alumina chip (
If the difference in the coefficient of thermal expansion (6 to 7 x 10-6/°C) is large, defects such as cracks or peeling will easily occur at the connection between the component and the board due to thermal changes during use.

To improve this, a ceramic-coated thermoplastic resin laminate was proposed in which a ceramic layer was formed by thermal spraying ceramic on one side of metal foil, a thermoplastic resin prepreg was attached to the ceramic layer, and the ceramic layer was integrated by pressing. This method made it possible to improve dimensional stability.

<<Problems to be Solved by the Invention>> However, in the method described above in which the ceramic layer and the thermoplastic brevreg layer, which is a thermoplastic resin-impregnated base material layer, are directly integrated by press molding, the ceramic layer and the thermoplastic resin base material A problem arose that the adhesion of the layers was insufficient.

Thermoplastic resins tend to soften more easily when heated than thermosetting resins, and melt at temperatures above their melting point.

However, the viscosity of the resin at that time is generally more than 100 times greater than the viscosity of the liquid thermosetting resin immediately before curing, and has very poor fluidity. Therefore, even if the thermoplastic resin-impregnated base material layer and the ceramic layer are directly stacked and integrated with the ceramic layer using only the resin impregnated into the base material, strong adhesion cannot be achieved.

Furthermore, if the pressing force and heating temperature are increased too much in order to increase the adhesion peak, the fibers of the base material will be disturbed and the resin will deteriorate, which is unfavorable in terms of the properties of the laminate.

Therefore, the present invention proposes a thermoplastic resin laminate with excellent dimensional stability, in which a ceramic layer and a thermoplastic resin-impregnated base material layer are integrated with sufficient adhesion.

<Means for Solving the Problems> The thermoplastic resin laminate according to the present invention includes forming a ceramic layer on one side of a metal foil, filling the voids of the ceramic layer with a thermoplastic resin, and then applying a thermoplastic resin to the surface of the ceramic layer. Technical measures have been taken to provide and integrate a resin-impregnated base material layer.

In other words, instead of directly integrating the ceramic layer and the thermoplastic resin-impregnated base material layer, the ceramic layer is first filled with thermoplastic resin into the minute voids in the ceramic layer, and then integrated with the thermoplastic resin-impregnated base material layer. It is characterized by improved adhesion between the layer and the base material layer.

The ceramic layer and the thermoplastic resin-impregnated base layer are made of different materials, including inorganic and organic materials, and no suitable adhesive has been found.

For example, a material with low viscosity and high adhesiveness, such as a liquid thermosetting resin just before hardening, penetrates well into the voids of the ceramic layer, but the adhesiveness with the thermoplastic resin is poor and the effect is low. Therefore, it is a very effective means to fill the voids of the ceramic layer with a resin of the same type as the resin of the thermoplastic resin-impregnated base material layer before the ceramic layers are integrated. The resin in the voids not only improves the adhesion between the ceramic layer and the thermoplastic resin-impregnated base material layer, but also has the effect of improving the adhesion with the metal foil, thereby improving the so-called beer strength.

Next, the present invention will be explained in detail.

Metal foils include copper, aluminum, iron, stainless steel,
Foils of metals or alloys such as nickel, silver, invar alloy, and 42 alloy are used, but copper foil is most commonly used as the circuit part of printed circuit boards, and is the most suitable because it is inexpensive. .

The ceramic layer formed on the metal foil may be a sintered ceramic plate bonded to the metal foil. However, the ceramic layer formed by thermal spraying has good adhesion to the metal foil, and the internal voids are large at 5 to 2 Qvol%, so it is easy to fill with thermoplastic resin and is highly suitable for improving adhesion. .

The types of ceramics to be sprayed include alumina, titania, silica, zirconia, magnesia, calcia, spinel,
Mullite, barium titanate, etc. are used.

Thermoplastic resins are required to have half-111 heat resistance as electronic materials, so the higher the melting point, the better, especially at 200°C.
Resins having the above properties are suitable. This is common to resins used for thermoplastic resin layers and base material layers.

The type of resin has a low dielectric constant and dielectric loss tangent, and a melting point of 27.
Fluororesins with a temperature of 0°C or lower are particularly preferred.

However, other resins with high melting points such as polysulfone resin, polyethersulfone resin, polyetherimide resin, polyetherether resin, and polyphenylene sulfide resin can be used.

Further, the resin used for the thermoplastic resin layer is preferably the same resin as the base layer or the same type of resin from the viewpoint of adhesion. However, they may be different as long as the adhesion can be satisfied.

For example, P with a melting point of 327°C is used as a resin to be impregnated into the base material layer.
TFE resin (tetrafluoroethylene propylene resin) can be used, and FEPIat resin (fluorinated ethylene propylene resin) having a melting point of 270° C. can be used as the thermoplastic resin to fill the voids of the ceramic layer. In this way, when a fluororesin of the same type as the base material layer is used and the melting point of the thermoplastic resin filled into the voids of the ceramic layer is lower than the melting point of the resin of the base material layer, the adhesion is further improved.

To fill the voids in the ceramic layer with thermoplastic resin, apply a solution containing fine thermoplastic resin powder dissolved in a solvent.
The easiest and best method is to evaporate the solvent. In particular, when using a fluororesin, a method can be used in which a dispersion of, for example, PTFE or FEP is applied as the fluororesin from the surface of the ceramic layer, and moisture is vaporized by heating and drying.

"Example" An embodiment of the present invention will be explained with reference to FIG.

The one in Figure 1 consists of a copper foil 1 on the outer surface, a ceramic layer 2 formed on the inner surface by a thermal spraying method and with the voids filled with FEP resin 3, and a glass cloth base material provided on the inner surface. The copper clad laminate is composed of a layer 4 impregnated with PTFE resin, and these layers are integrated. In the ceramic layer 2, an FEP dispersion is applied and dried to fill the voids with FEP resin 3.

The copper foil 1 is an electrolytic copper foil having a thickness of 35 μm, and the surface in contact with the ceramic layer 2 is roughened.

The ceramic layer 2 is a layer in which alumina (8!203) is thermally sprayed on the copper foil 1, and has a thickness of 50 μm. The proportion of the void in the ceramic layer 2 is 15 vol %, and this void is filled with the FEP resin 3. The surface is also coated with a 15 μm thick FEP resin layer.

Layer 4, which is a glass cloth base material impregnated with PTFE resin, has a thickness of 0.
．． It is 7mn. This layer 4 is a lamination of glass cloth base materials impregnated with PTFE, and the resin content is 70 vo.
It is 1%.

In order to confirm the adhesion of the laminate, after 60 cycles of Hottu 1 oil thermal shock test (alternate immersion in room temperature water and 260°C silicone oil), we examined the occurrence of peeling, cracks, etc., but no abnormalities were observed. It was in good condition. The coefficient of thermal expansion in the plane direction of this laminate is 12 x 10'/'C, and the coefficient of thermal expansion of this laminate is 12 x 10'/'C.
6/°C) to approximately 1/2. Further, the dielectric constant was 2.6, the dielectric loss tangent was 0.0002, and the beer strength was 1.4 kgf/crl.

For comparison, FIG. 2 shows a laminate that is completely the same as the example except that the ceramic layer 2 is not filled with FEP resin. After 60 cycles of a thermal shock test using hot oil to confirm the adhesion of the laminate, it peeled off. The occurrence of cracks, etc. was investigated. As a result, slight delamination was confirmed between the ceramic layer (alumina layer) and the glass cloth fluororesin layer. Other characteristics include beer strength of 0.6
kg['/cJ, but was almost the same as the example.

<<Effects of the Invention>> As described above, according to the present invention, the voids of the ceramic layer are filled with a thermoplastic resin and then the thermoplastic resin-impregnated base material layer is integrated. Compared to a plate, the adhesion between the ceramic layer and the thermoplastic resin-impregnated base material layer and beer strength are improved, and the coefficient of thermal expansion in the planar direction is approximately 1/2 that of a thermoplastic resin laminate that does not use a ceramic layer. This makes it possible to provide a laminate with improved stability, low dielectric constant and low dielectric loss tangent, and excellent electrical properties.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a thermoplastic resin laminate of the present invention, and FIG. 2 is a sectional view of a laminate showing the structure of a comparative example. 1... Copper foil 2... Ceramic layer 3... FEP resin 4... PTFE resin impregnated glass cloth base material layer (thermoplastic resin impregnated base material layer), -i

Claims (1)

[Claims] 1. A ceramic layer is formed on one side of a metal foil, the voids in the ceramic layer are filled with a thermoplastic resin, and a thermoplastic resin-impregnated base material layer is provided on the surface to integrate the metal foil. A thermoplastic resin laminate characterized by: 2. The thermoplastic resin laminate according to claim 1, wherein the metal foil is copper foil. 3. The thermoplastic resin laminate according to claim 1, wherein the ceramic layer is a thermally sprayed layer. 4. The thermoplastic resin laminate according to claim 1, wherein the thermoplastic resin has a melting point of 200°C or higher. 5. The thermoplastic resin laminate according to claim 1, wherein the resin filling the voids in the ceramic layer is a resin having a lower melting point than the resin in the resin-impregnated base material layer. 6. The thermoplastic resin laminate according to claim 1, wherein the resin filling the voids in the ceramic layer is the resin remaining after the moisture in the fluororesin dispersion has been volatilized.