JPH03231843A - Fluororesin laminated sheet - Google Patents

Abstract

PURPOSE:To produce fluororesin laminated sheet, the permittivity of which is small, by a method wherein metal foil is laminated onto one side or both sides of fluororesin-impregnated fiber base material layer, which contains fine inorganic filler powder having specified physical properties, so as to be made into an integral body under heat and pressure. CONSTITUTION:Water soluble dispersing liquid of fluororesin is prepared, to which fine inorganic filler powder having characteristic values such as permittivity of 2 - 4, specific gravity of 1.5 - 3.0, mean particle diameter of 0.05 - 9mum and thermal expansion coefficient of (2 - 20)X10<-6>/ deg.C is added. After fiber base material is impregnated with said water soluble dispersing liquid of fluororesin, fluororesin prepregs consisting of the impregnated base material are laminated to one another so as to provide metal foil on both sides or one side of it in order to be made into an integral body under heat and pressure, resulting in producing fluororesin laminated sheet. Concretely, copper-clad lami nated sheet, which is produced by integrating copper foils 1 on outer surfaces with fluororesin base material layer 2, to which fine molten silica powder is added and which is formed on the inner surface of each of the foils, is exam pled.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a fluororesin laminate and a method for manufacturing the same.

(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 a thermosetting resin such as phenol resin, epoxy resin, or polyimide resin, and then using a metal such as copper foil on the back side. Foil-covered laminates have been widely used.

However, recently, instead of the conventional laminates mainly made of thermosetting resins, laminates in which the fiber base material is impregnated with fluororesin have attracted attention. This is because the laminate using this fluororesin has the following features.

That is, fluororesin has 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, fluororesin substrates with low dielectric constants and low dielectric loss tangents are attracting attention.

However, even the fluororesin laminate having such features has 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 the most common glass cloth-based fluororesin laminate is 50 to 70X10-''/'C, and that of glass cloth-based thermosetting resin laminates made of epoxy resin, polyimide resin, etc. is 10 to 15X10. -“/' Larger than C. This results in a decrease in connection reliability with components connected on the board. If there is a large difference in the thermal expansion coefficient between the silicon chip (thermal expansion coefficient 3.5 x 10-'/'C) connected to the substrate and the alumina chip (thermal expansion coefficient 6-7 x 10-'/'C), the Defects such as cracks or peeling are likely to occur at the connections between components and substrates due to thermal changes.

Moreover, if the coefficient of thermal expansion is large, the dimensional stability will decrease when the substrate is multilayered, which is undesirable.

Therefore, in order to improve this problem, a method was proposed in which an inorganic light agent was added to the fluororesin.

(Problems to be Solved by the Invention) As this filler, fine powders of titania (Tie) and barium titanate (BaTiO*) have conventionally been used. However, these are JP-A-62-19451 (B
There is a problem that the dielectric constant becomes large (as disclosed in 2003) (addition of aTiOs), and the characteristic of fluororesin laminates, which can reduce the dielectric constant, is lost, and the effect of improving dimensional stability is not clear. There wasn't.

In particular, when using fluororesin laminates to speed up computer signal transmission, the signal transmission speed is inversely proportional to the square root of the dielectric constant, so a material with a dielectric constant of 4 has a transmission speed of 77% compared to a material with a dielectric constant of 2.4. %. In addition, such computer substrates are required to be highly sophisticated, and are required to have a high number of layers and dimensional stability. Therefore, with conventional fillers, it was not possible to fully satisfy high speed and dimensional stability.

Therefore, an object of the present invention is to propose a fluororesin laminate containing an inorganic filler that has a small dielectric constant and excellent dimensional stability.

(Means for Solving the Problems) The fluororesin laminate according to the present invention has a dielectric constant of 2 to 4, a specific gravity of 1.5 to 3.0, an average particle size of 0.05 to 9 μm, and a coefficient of thermal expansion of 2 to 20 x 10. -' We have taken a technical measure of adding 110C inorganic light 1 agent fine powder to fluororesin.

In other words, we use an inorganic filler that has a specific gravity and particle size similar to the fluororesin in the fluororesin die version, making it easy to disperse in the dispersion, and also has a dielectric constant close to that of the fluororesin and a small coefficient of thermal expansion. A major feature is that

By adding this filler, it becomes possible for the first time to reduce the coefficient of thermal expansion without changing the low dielectric constant, which is a characteristic of fluororesin laminates. This makes it possible to provide a substrate that has excellent dimensional stability and a low dielectric constant, and is suitable for high-speed computing computers.

(effect) Next, the present invention will be explained in detail.

As the fluororesin, tetrafluoroethylene 4UH (Tpg
), fluorinated ethylene propylene resin (pgp), perfluoroalkoxy resin jff (pFA), etc., but TFF
i has a high melting point and is most commonly used. Moreover, these may be used in combination. Fluororesin dispersion is made by dispersing fluororesin in water in the form of fine powder. In the case of TFE, the particle size of the fine powder is about 0°2 μm and the specific gravity is 2.1, and it is usually dispersed in water as a resin component. 50-6
0. It is commercially available in the form of t% dispersion.

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

As the inorganic filler, the dielectric constant of the fluororesin is 2.1, so it is preferable to use an inorganic filler of about 2 to 4. Adding more than 4 is not preferable because the dielectric constant of the laminate increases. Further, although the filler may be 2 or less, no suitable filler with 2 or less has been found.

Regarding the specific gravity, since the specific gravity of the fluororesin is 2.1, a value close to that of 1.5 to 3.0 is suitable for easy dispersion. If it is less than 1.5, the apparent specific gravity in the fine powder state becomes even lighter, which makes it difficult to uniformly disperse it in a dispersion, and it also tends to separate even after dispersion, which is not preferable. On the other hand, if the specific gravity is higher than 3.0, the filler tends to settle after being dispersed into the dispersion, which is not preferable.

Regarding the average particle size, since the particle size of the fluororesin fine powder in the dispersion is 0.05 to 0.5 μm, the particle size of the filler is also suitably 0.05 to 9 μm. 0.05μ
If the particle size is less than m, the particle size is too small to float and be difficult to disperse in a dispersion. Moreover, if the particle size is 9 μm or more, the particle size is too large compared to the fluororesin fine powder and it is difficult to uniformly disperse it, which is not preferable.

Fillers are added to reduce the coefficient of thermal expansion of the laminate, so it is better if the coefficient of thermal expansion of the filler is also small.
2 to 20 x 10” /'C is good. 2 x 10
-' or less is acceptable, but no suitable filler has been found. Further, if the amount is 20 X IF' or more, the effect of addition is small and is not preferable.

The amount of filler added is 10 to 10 to the fluororesin to be mixed.
0% by volume is suitable. It may be less than 1096, but the effect will be less. Moreover, if it is added in an amount of 100% or more, it is difficult to uniformly disperse it, which is not preferable.

The most suitable fiber base material to be used is glass fiber woven fabric. Glass fiber woven fabrics are available in many types of glass fiber materials, woven fabric thicknesses, and fabric weights, and are suitable for manufacturing various fluororesin laminates. Suitable materials for these fillers include shot fine powder of fused silica. Fused silica fine powder has a dielectric constant of 3.5, a specific gravity of 2.2, and an average particle size of 3 μm.
, a coefficient of thermal expansion of 4 x 10'-''17°C, satisfying various requirements.Furthermore, since fused silica is softer than crystalline silica, it has good machinability and is suitable as a laminate material.

Furthermore, since fluororesin has a low elastic modulus and is soft, it has poor cutting properties for glass fibers during machining. Therefore, by adding a filler, the elastic modulus of the resin layer becomes thicker, and the cutting properties of glass fibers are improved.

In particular, through-hole drilling has improved drilling processability,
The surface roughness of the inner wall of the hole is improved.

(Example) An embodiment of the present invention will be described with reference to FIG.

FIG. 1 shows a copper-clad laminate in which a copper foil 1 on the outer surface and a fluororesin base layer 2 added with fine fused silica powder formed on the inner surface are integrated.

The fluororesin base material layer is made by pressing and heating glass cloth impregnated with fluororesin to integrate it.

Next, a method for manufacturing this fluororesin laminate will be described.

Tetrafluoroethylene (T F E') Resin tispersion (Mitsui Fluorochemical Co., Ltd.) and fused silica fine powder (Tatsumori Co., Ltd.): dielectric constant 3.5, specific gravity 2.2, average particle size 3 μm, thermal expansion coefficient 4"10-'17C is added. The amount added is 25% by volume based on the TFB resin. A glass cloth (manufactured by Nittobo Co., Ltd.) with a thickness of 0.1 mm is immersed in this dice version, and dried and fired. A fluororesin prepreg with fused silica fine powder added was prepared. This prepreg has a thickness of 0.13 mm. Eight sheets of this prepreg were laminated, and copper foil with a thickness of 35 μm was provided on both sides of the prepreg.
cnl, and are integrated by pressurizing and heating at 400°C to produce a fluororesin laminate with a thickness of 1st grade.

The characteristics of this fluororesin laminate are a dielectric constant of 2.8 (IMHz
), dielectric loss tangent 0.0003 (1MH,) thermal expansion coefficient 3
It had excellent properties such as 0x10" 17°C, insulation resistance 6x10"°Ω, and copper foil peeling strength of 1.8 and 4 f/cm.

Next, a comparative example will be shown.

A laminate of a comparative example is shown in FIG. All experiments were carried out under the same conditions as in the examples except that fused silica was not added to the die version. The characteristics of this fluororesin laminate are a dielectric constant of 2.6, a dielectric loss tangent of 0°0003, and a coefficient of thermal expansion of 60 x
10-" 17°C, insulation resistance 7 x 10"Ω, copper foil peeling strength 1.9 Klf/crn.

The thermal expansion coefficient of the example is significantly reduced to 1/2 compared to the comparative example, but the dielectric constant is also low at 2.8, and other properties are the same as those of the laminate without filler.

Furthermore, the surface roughness of the inner wall of the hole when drilling a through hole was 20 μm in the example and 28 μm in the comparative example, which was better in the example.

(Effects of the Invention) According to the method of the present invention, compared to conventional fluororesin laminates, the coefficient of thermal expansion is approximately 1/2, dimensional stability is improved, and the drilling workability of through holes is also improved. A laminate with excellent electrical properties was obtained without increasing the ratio.

[Brief explanation of drawings]

FIG. 1 is a laminated configuration diagram showing the configuration of an example of the present invention, and FIG. 2 is a laminated configuration diagram showing the configuration of a comparative example. 1... Copper foil, 2... Fused silica fine powder human base material layer, 3
...Fluororesin base material layer

Claims (1)

[Claims] 1. Dielectric constant 2-4, specific gravity 1.5-3.0, average particle size 0.
05~9μm, thermal expansion coefficient 2~20×10^-^6/℃
A fluororesin prepreg made of a fiber base material impregnated with a fluororesin dispersion (water-soluble dispersion) containing fine inorganic filler powder is laminated, metal foil is placed on both or one side of the fluororesin prepreg, and they are integrated by pressure heating. A method for manufacturing a fluororesin laminate, characterized by the following. 2, dielectric constant 2-4, specific gravity 1.5-3.0, average particle size 0.
1. A fluororesin laminate, characterized in that a fiber base material layer impregnated with a fine inorganic filler powder of 0.05 to 9 μm and a fluororesin is provided with metal foil on both or one side of the fiber base material layer and is integrated with the fiber base material layer. 3. The method for producing a fluororesin laminate according to claim 1, wherein the amount of the inorganic filler added to the fluororesin dispersion is 10 to 100% by volume based on the fluororesin. 4. The method for producing a fluororesin laminate according to claim 1, and the fluororesin laminate according to claim 2, wherein the fiber base material is a glass fiber woven fabric. 5. The method for producing a fluororesin laminate according to claim 1, and the fluororesin laminate according to claim 2, wherein the metal foil is copper foil. 6. The method for producing a fluororesin laminate according to claim 1, and the fluororesin laminate according to claim 2, wherein the inorganic filler is fused silica (SiO_2) fine powder.