JPH04168128A - Prepreg and its use - Google Patents

Abstract

PURPOSE:To obtain the subject prepreg bondable at low temperature under low pressure and capable of shortening the working time by combining a prepreg obtained by impregnating a specific ethylene polymer in a cloth substrate with a prepreg having plural fluororesin layers. CONSTITUTION:Layers 4 of a tetrafluoroethylene-hexafluoropropylene copolymer (abbreviated to FEP) or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer are formed on a cloth substrate 3 and each layer 4 is further laminated with a polytetrafluoroethylene layer 5 (abbreviated to PTFE) and an FEP layer 6 to form the 1st prepreg 1. The objective prepreg can be produced by laminating the 1st prepreg layers on both surfaces of a 2nd prepreg 2 produced by impregnating a PTFE layer 5 in a cloth substrate 3.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a prepreg suitable for manufacturing various devices that utilize high frequency ranges such as electronic devices, communication devices, and computers, and a laminate and a circuit using this prepreg. Concerning boards and multilayer circuit boards.

[Conventional technology]

Conventionally, various types of equipment that utilize high frequency ranges have been manufactured by laminating a prepreg made of glass cloth impregnated with polytetrafluoroethylene (hereinafter referred to as PTFE), with copper foil placed on the surface of the prepreg, and then integrated by heat and pressure. A circuit board is used in which the copper foil of this laminated board is patterned (Japanese Patent Laid-Open No. 60-248346).

Further, this circuit board may be used as an inner layer circuit board, and a multilayer circuit board may be obtained by providing a copper foil pattern on the surface of the inner layer circuit board via a prepreg similar to that described above.

[Problem to be solved by the invention]

By the way, when manufacturing the above-mentioned laminate board or multilayer circuit board, it is necessary to bond PTFE and copper foil or PTFE and the inner layer circuit board, and therefore, the temperature during the heating and pressing operation is naturally the melting point of PTFE. As mentioned above, in practice, a high temperature of about 380 to 400°C is required, and the pressure is also high, about 10 to 80) cg/cid. For this reason, complicated and expensive manufacturing equipment had to be installed. Furthermore, there was also the problem that it took a long time to sufficiently bond and the productivity was poor.

[Means to solve the problem]

As a result of intensive research in order to solve the above problem, the present inventor has found that by combining a prepreg in which a cloth-like base material is impregnated with PTFE and a prepreg in which a multi-layered fluororesin layer is formed on a cloth-like base material, the desired result can be achieved. The inventors have discovered that the object of the invention can be achieved, and have completed the present invention.

That is, the prepreg according to the present invention has a cloth-like base material containing a tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter referred to as FEP) or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter referred to as P
A first prepreg is formed with a layer made of FA (referred to as FA), and a PTFE layer and an FEP layer are further provided on the layer, and is superimposed on both sides of a second prepreg, which is a fabric-like base material impregnated with PTFE. It is characterized by consisting of:

In the present invention, cloth-like base materials conventionally used as prepreg materials can be used as they are. Specific examples of such cloth-like base materials include inorganic fibers such as glass fiber, asbestos fiber, alumina fiber, boron fiber, boron nitride fiber, silicone carbide fiber, and titania fiber, or aromatic polyamide fiber (aramid fiber). PTFE
Examples include woven fabrics and non-woven fabrics consisting of single threads of organic fibers such as fibers, ultra-high molecular weight polyethylene fibers, and aromatic polyester fibers, or composite threads using two or more of these fibers. The thickness of this base material is selected appropriately, but is usually about 50~
It is 200 μm.

The multi-layer prepreg according to the present invention has two
It is composed of two different types of prepreg.

In the first prepreg, an FEP layer (hereinafter referred to as the first FEP layer) or a PFA layer is formed on a cloth-like base material, and a PTFE layer and a FEP layer (hereinafter referred to as the second FEP layer) are formed on the layer. ) was formed.

An impregnation method can be employed to form the first FEP layer or PFA layer on the cloth-like base material to obtain the first prepreg.

When the amount of FEP or PFA impregnated into the fabric base material is large,
These penetrate into the fibers constituting the base material and form a relatively thick layer on the surface of the base material, and when the base material has a network, they may block this network. On the other hand, when the amount of FEP or PFA impregnated is small, they penetrate into the fibers constituting the base material and form a relatively thin layer on the surface thereof.

Impregnation of FEP or PFA into a fabric-like substrate can be achieved, for example, by (
(b) A method of dipping the cloth-like base material in FEP or PFA dispersion, pulling it up, and then heating it at a temperature equal to or higher than the melting point of FEP or PFA (repeating dipping and heating if desired); (b) cloth-like base material; FEP or PFA material
A method of spraying dispersion and then heating at a temperature equal to or higher than the melting point of FEP or PFA (if desired, repeating the application and heating), (c) fabric-like base material and FEP
Overlap EP or PFA sheets, then FEP
Alternatively, it can be carried out by a method of heating at a temperature higher than the melting point of PFA.

Then, the first FEP layer or P
A PTFE layer and a second FEP layer are further sequentially formed on the FA layer. The PTFE layer or the second FEP layer can be formed using a PTFE or FEP dispersion or sheet according to the methods (a) to (c) above.

The impregnation rate of these fluororesins into the cloth-like base material is appropriately set depending on various factors, but is usually about 55 to 85%.

This impregnation rate is the weight M0 of the fabric base material before being impregnated with fluororesin,
First FEP layer or PFA layer, PTFE layer and second
This is a value calculated using the following formula (I) using the weight M of the cloth-like base material after forming the FEP layer.

Note that the first FEP layer or P
The impregnation ratio of FEP or PFA, PTFE and FEP for forming the FA layer, PTFE layer and second FEP layer is such that the ratio of FEP or PFA for forming the first FEP layer or PFA layer to the total weight of impregnated fluororesin is about 5 to
25% by weight, the proportion of PTFE for forming the PTFE layer is approximately 60%
~93% by weight, the proportion of FEP for forming the second FEP layer is approximately 2
It can be set to 15% by weight.

The prepreg of the present invention has the above first prepreg on both sides of the second prepreg.
The second prepreg is a fabric-like base material impregnated with PTFE and a layer formed on the surface of the base material can be used as the second prepreg. The impregnation rate of PTFE into the cloth-like base material in the second prepreg is also
Using the weight before and after impregnation with FE, the formula (I)
It can be calculated in the same way. This impregnation rate is usually about 55
~85%.

FIG. 1 shows an example of a multilayer type prepreg according to the present invention, in which first prepregs 1 are stacked on both sides of a second prepreg 2, and these are integrated by heating and pressing.

The prepreg according to the present invention shown in FIG.
As a prepreg, as shown in FIG. 2, first a first FEP layer (or PFA layer) 4 is formed on a cloth-like base material 3, and then a PTFE layer 5 and a second FEP layer 6 are formed on the layer 4 in this order. The second prepreg used was one in which a PTFE layer 5 was formed on a cloth-like base material 3 as shown in FIG.

In this example, PTFE is used as the second prepreg for the cloth-like base material.
Although a single layered layer is used, in the present invention, these predetermined layers can also be used in a stacked manner.

Moreover, a plurality of sheets of the first prepreg can be stacked on both sides of the second prepreg.

The invention also provides a laminate. This laminate uses, for example, a multilayer type prepreg in which the first prepreg 1 is superimposed on both sides of the second prepreg 20 as shown in FIG. 4, and a metal layer 7 made of copper foil or the like is provided on both sides of the prepreg. It has a unique structure.

Additionally, the present invention also provides a circuit board. For example, as shown in FIG.
It has a structure in which a metal pattern 8 is provided on the surface (both sides in the figure) of a multilayer prepreg made by overlapping prepregs 1.

Such a circuit board can be obtained by using a laminated board as shown in FIG. 4 and patterning the metal layer thereof.

Patterning of the metal layer can be carried out using a peel-off developing type photoresist, a solvent developing type photoresist, or an alkali developing type photoresist, as in the conventional manufacturing of printed circuit boards. For example, an alkali-developable photoresist layer is formed on the surface of the metal layer of a laminate,
The photoresist is then exposed to light in a pattern through a photomask, the unexposed portions of the photoresist are then dissolved and removed to partially expose the metal layer, the exposed portions of the metal layer are removed by etching, and the photoresist is further removed by etching. By removing the exposed portions with a solvent, a circuit board having a metal pattern corresponding to the exposed pattern of the photoresist can be obtained.

The present invention also provides a multilayer circuit board using a circuit board as shown in FIG. 5 as an inner layer. For example, as shown in FIG. 6, this multilayer circuit board uses a circuit board having metal patterns 8 on both sides of the second prepreg 2 via the first prepreg as an inner layer, and further coats the first prepreg 1 on the surface of the circuit board. A structure may be provided in which the metal pattern 8 is provided therebetween.

〔Effect of the invention〕

In the present invention, a PTFE layer is formed on the cloth-like base material on both sides of the second prepreg in which a PTFE layer is formed on the cloth-like base material.
It has a structure in which first prepregs are layered with A layer, PTFE layer, and FEP layer in this order, and the outermost layer is FEP.
Therefore, not only can the bonding be performed at low temperature and pressure, but also the working time can be shortened.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example (Manufacture of the first prepreg) A glass cloth with a thickness of about 50 μm is immersed in an aqueous dispersion having a FEP powder concentration of 40% by weight, pulled up, and heated at a temperature of 320°C for 2 minutes to produce the first FEP.
form a layer.

Next, this is immersed in an aqueous dispersion having a PTFE powder concentration of 60% by weight, pulled up, and heated at a temperature of 380° C. for 2 minutes. Then, this dipping and heating are repeated three more times to form a PTFE layer.

This was then immersed in the same FEP dispersion as above, pulled up, and heated at a temperature of 320°C for 2 minutes to form a second FEP layer to a thickness of 72 μm.
m first prepregs are obtained.

The impregnation rate of fluororesin in the first prepreg is 70%, and the percentage of FEP for forming the first FEP layer, PTFE for forming the PTFE layer, and FEP for forming the second FEP layer is 70% in the total weight of the fluororesin impregnated into the glass cloth. The percentage is
They were 14.5% by weight, 78.5% by weight, and 7% by weight.

(Manufacture of second prepreg) Using the same glass cloth and PTFE dispersion as above, the glass cloth is immersed in the dispersion, pulled up, and heated at a temperature of 380° C. for 2 minutes.

Then, by repeating this dipping and heating four more times, a second prepreg in which a PTFE layer is formed on the glass cloth is obtained. This second prepreg has a thickness of approximately 70 μm.
, the PTFE impregnation rate was 68%.

(Manufacture of laminate) Nine second prepregs are stacked, and the first prepreg and 18 μm thick &PI foil are placed on both sides of the stack.

Then, a laminate is obtained by heating and pressing for 30 minutes at a temperature of 385° C. and a pressure of 50 kg/cd.

(Manufacture of circuit board) ``A circuit board is obtained by patterning both copper foils in the laminate using an alkali-developable photoresist.

(Manufacture of multilayer circuit board) A first prepreg with a thickness of 18 μm is coated on both sides of the above circuit board.
Copper foils were placed on each side at a temperature of 300°C and a pressure of 15kg/
These are integrated by heating and pressurizing them for 15 minutes under C11 low temperature and low pressure conditions.

Next, a multilayer circuit board was obtained by patterning the copper foils on both outer surfaces using an alkali-developable photoresist.

Comparative Example (Manufacture of Laminate) A laminate was obtained in the same manner as in the Example except that the first prepreg was not used.

In addition, the temperature at this time is 385'C1 pressure is 50kg/
cd, heating and pressurizing time was 30 minutes.

(Manufacture of circuit board) A circuit board was obtained in the same manner as in the example except for using this laminate.

(Manufacture of multilayer circuit board) A second prepreg with a thickness of 18 μm is coated on both sides of this circuit board.
Copper foils were placed respectively at a temperature of 390°C and a pressure of 50kg/
A multilayer circuit board was obtained by heating and pressurizing for 45 minutes under CD high temperature and high pressure conditions.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of prepreg according to the present invention,
2 and 3 are cross-sectional views schematically showing the structures of the first and second prepregs used to manufacture the prepreg shown in FIG. 1, and FIGS. FIG. 2 is a cross-sectional view showing an example of a laminate, a circuit board, and a multilayer circuit board according to the invention.

Claims (4)

[Claims] (1) A layer made of a tetrafluoroethylene-hexafluoropropylene copolymer or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is formed on a cloth-like base material, and a polytetrafluoroethylene layer and a tetrafluoroethylene layer are further formed on the layer. A prepreg in which a first prepreg provided with a fluoroethylene-hexafluoropropylene copolymer layer is laminated on both sides of a second prepreg in which a cloth-like base material is impregnated with polytetrafluoroethylene. (2) A laminate comprising the prepreg according to claim 1 with a metal layer provided on the surface thereof. (3) A circuit board comprising a metal pattern provided on the surface of the prepreg according to claim 1. (4) A multilayer circuit board comprising a metal pattern provided on the surface of the circuit board according to claim 3 via the prepreg according to claim 1.