JP3909246B2 - PTFE resin laminate manufacturing method and PTFE resin laminate - Google Patents

Description

【００３６】
試験方法
曲げ弾性率：ＪＩＳ規格Ｋ６９１１５．１７（熱硬化性プラスチック一般試験方法）に準拠して行った。
熱膨張率：リガク製ＴＭＡ試験記を用いて、３０℃〜２６０℃間厚さ方向の膨張を測定し、原厚に対する変化率で示した。
【００３７】
【発明の効果】
以上のように、この発明によると、ＰＴＦＥ樹脂積層板に放射線を照射し、これをアニーリングすることによって曲げ弾性率を増大させるとともに熱膨張率を低減させることが可能となり、これにより従来高周波機器用に用いられているＰＴＦＥ樹脂積層板の問題点である加工工程中の取扱い性やドリル加工性、さらにスルーホール信頼性を改善することが可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a PTFE resin laminate suitable for use in high-frequency equipment or the like having a high elastic modulus and a low coefficient of thermal expansion.
[0002]
[Prior art]
A fluororesin is an industrial polymer material having very specific properties among polymer compounds, and various applied products are provided on the market.
[0003]
In particular, typical PTFE (polytetrafluoroethylene) resin, which accounts for 70% of the fluororesin demand, has characteristics that are not found in other engineering plastics, such as a melting point of 327 ° C. and a dielectric constant of 2.1 (1 MHz). Its specific characteristics are excellent in heat resistance, chemical resistance, solvent resistance, moisture resistance, low dielectric properties, insulation, abrasion resistance, slipperiness, non-adhesiveness, water repellency, weather resistance, purity, etc. It is mentioned.
[0004]
Various PTFE resin products that take advantage of these characteristics are diverse, and fluororesin parts such as films, sheets, laminates, laminates with metal foil, and pipes are used in many industrial fields. There are no other materials.
[0005]
In particular, in the field of laminates used in high-frequency equipment, copper-clad PTFE resin laminates that are superior in terms of dielectric properties are mainly used, and the demand is expected to expand in the advanced information and communications society in the future. ing.
[0006]
However, the fluororesin consists essentially of a flexible polymer chain and has the disadvantage that its elastic modulus is low. For this reason, for example, a thin laminated plate is not stiff, and it is difficult to handle in a processing step, such as bending and warping.
[0007]
In addition, the manufacturing process becomes complicated and there are many problems in processing, such as caulking does not work and it is necessary to perform caulking using special tools and parts.
[0008]
On the other hand, since it is thermoplastic, there is also a problem that the thermal expansion coefficient of the fluororesin itself is large, the through-hole reliability is low, and it cannot be used for applications where heat history is applied.
[0009]
Several countermeasures for these problems have been made public, for example, a method of compounding and reinforcing by adding a filler such as an inorganic filler is used. In addition to the increase, the cost is increased and sufficient practical performance cannot be obtained.
[0010]
Further, in order to improve the elastic modulus of the fluororesin itself, the PTFE resin is irradiated with an electron beam at a high temperature just above 327 ° C. in an oxygen-free manner to crosslink PTFE molecules covalently, thereby increasing the strength and elastic modulus However, the oxygen-free high temperature condition is disadvantageous in the normal laminate manufacturing process.
[0011]
Therefore, PTFE resin laminates used for high-frequency devices and the like generally have the disadvantages of low elastic modulus and high thermal expansion coefficient.
[0012]
[Problems to be solved by the invention]
Therefore, the present invention maintains high electrical properties such as low dielectric constant and low dielectric loss tangent, and improves workability and through-hole reliability, has high elastic modulus, low thermal expansion coefficient, high frequency equipment, etc. It is an object of the present invention to provide a method for producing a PTFE resin laminate that can be suitably used for the above applications.
[0013]
[Means for Solving the Problems]
As a result of various studies to solve the above-mentioned problems, the present invention irradiates a laminated board obtained by laminating a plurality of PTFE resin prepregs and heating and pressurizing them, followed by annealing treatment. Thus, it has been found that the elastic modulus of the PTFE resin laminate can be increased and the coefficient of thermal expansion can be reduced to improve the handleability, drilling workability and through-hole reliability in the working process.
[0014]
That is, the PTFE molecular chain in the amorphous region is activated in thermal motion by annealing, and a part thereof is secondarily crystallized if there is a crystallization region in the vicinity. In addition, since the PTFE molecular chain in the amorphous region partially cut by irradiation with an appropriate amount of electron beam or γ-ray becomes easy to move, secondary crystallization can be performed even at room temperature if there is a crystallization region in the vicinity. it can.
[0015]
Thus, the thermal recrystallization of PTFE molecules in the crystal / amorphous interface region can be promoted by the combined use of annealing and radiation irradiation.
[0016]
As the secondary crystallization proceeds, the degree of crystallinity of the PTFE resin increases, and the intermolecular force as a whole increases. As a result, it is considered that molecular motion against external stress and heat is suppressed, leading to an increase in elastic modulus and a decrease in thermal expansion coefficient.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
In the PTFE resin prepreg used in the present invention, a glass substrate made of glass fibers produced by a usual method is used. Although it does not limit as glass fiber, use of E glass is preferable if an electrical property, workability, and cost are considered. Aside from the price point, if glass fibers such as Q, D, T, NE, etc. are used for other insulating purposes, further improvement in dielectric properties can be achieved.
[0018]
Such glass fiber is used in the form of a woven fabric or a non-woven fabric. Woven fabrics include plain weave, twill weave, and satin weave.
[0019]
PTFE resin is usually supplied as a dispersion called dispersion, and the glass cloth base material wound in a roll shape is continuously drawn out and impregnated therein, followed by drying and baking processes. Is fixed. By repeating this impregnation step a plurality of times as necessary, a uniform and non-uniform PTFE resin prepreg can be obtained.
[0020]
Next, the obtained PTFE resin prepreg is cut into a predetermined size and, if necessary, one or a plurality of the prepregs are stacked, and these laminates are generally subjected to a vacuum at a temperature of about 300 ° C. under a predetermined pressure. And pressing for a predetermined time to obtain a PTFE resin laminate. In the case of a printed wiring board, a copper foil is laminated on the outer layer of the PTFE resin prepreg, and then heated and pressed in the same manner to obtain a copper-clad laminate.
[0021]
In these steps, the thickness of the laminate is not particularly limited, and the copper foil may be used only on one side or may not be used.
[0022]
Moreover, although the above-mentioned batch system is common as a press, even if it is a method of laminating a copper foil using a roll continuously, there is no problem.
[0023]
Furthermore, even if it is a multilayer board obtained by etching the surface of the obtained copper-clad laminate into a predetermined circuit pattern, performing drilling, etc. and then pressing again with a PTFE resin prepreg, there is no problem. .
[0024]
In this invention, the PTFE resin laminate produced by the above method is irradiated with a predetermined dose of radiation at normal temperature and pressure. As the radiation, α rays, β rays, γ rays, electron rays, X rays, and the like can be used. However, α rays and β rays have low visibility and are inefficient, so γ rays and electron beams are preferably used. Although gamma rays are used in this invention, it is more commercially preferred to use an electron beam that does not require a radiation source and whose dose control is relatively easy.
[0025]
A range of absorbed dose of 1 to 500 kGy can be used as the amount of γ-ray irradiation, but 10 kGy or more is appropriate in terms of efficiency, and if it exceeds 100 kGy, the physical properties of the PTFE resin are reduced, and 10 to 100 kGy is preferable.
[0026]
Irradiation can be performed by laminating alone or by laminating a plurality of sheets, and optimum conditions can be selected as appropriate.
[0027]
It is also a feature of the present invention that the PTFE resin laminate is annealed.
Specifically, the PTFE resin laminate is annealed in a heating furnace generally used in air and at normal pressure.
The combination of temperature and time is not particularly limited, but considering efficiency, it is preferably 1 to 5 hours at 250 to 320 ° C.
[0028]
By combining radiation irradiation and annealing, the intended effect can be obtained.
[0029]
As described above, the modified PTFE resin laminate can be easily obtained by using the apparatus normally used for the production of the PTFE resin laminate together with the modification step for increasing the elastic modulus and reducing the thermal expansion coefficient, which is the object of the present invention. Can be manufactured.
[0030]
【Example】
Examples of the present invention will be specifically described below, but the present invention is not limited thereto.
[0031]
Example A prepreg was prepared by impregnating, drying, and firing a PTFE resin dispersion (polyflon: manufactured by Daikin) in a 0.05 mm thick plain woven glass cloth (WE-05: manufactured by Nittobo) several times. A laminate in which 19 sheets of this prepreg sheet cut to a predetermined size were stacked and heated and pressurized at a temperature of about 300 ° C. under vacuum to obtain a 1.6 mm thick PTFE resin laminate. The laminated plate was irradiated with a γ dose corresponding to 50 kGy and subjected to an annealing treatment at 300 ° C. for 2 hours.
[0032]
Comparative Example 1
A prepreg was prepared by repeatedly impregnating a PTFE resin dispersion (polyflon: manufactured by Daikin) into a 0.05 mm-thick plain woven glass cloth (WE-05: manufactured by Nittobo) several times. A laminate in which 19 sheets of this prepreg sheet cut to a predetermined size were stacked and heated and pressurized at a temperature of about 300 ° C. under vacuum to obtain a 1.6 mm thick PTFE resin laminate.
[0033]
Comparative Example 2
It carried out like the comparative example 1 except having irradiated the gamma dose equivalent to 50 kGy.
[0034]
Comparative Example 3
The same procedure as in Comparative Example 1 was performed except that an annealing treatment at 300 ° C. × 2 hours was performed.
About the sample obtained by the Example and the comparative example, the bending elastic modulus and the thermal expansion coefficient were measured. The results are shown in Table 1.
[0035]
[Table 1]

[0036]
Test method Flexural modulus: Measured according to JIS standard K69115.17 (General test method for thermosetting plastics).
Thermal expansion coefficient: Using Rigaku's TMA test report, the expansion in the thickness direction was measured between 30 ° C. and 260 ° C., and indicated by the rate of change relative to the original thickness.
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to increase the flexural modulus and reduce the coefficient of thermal expansion by irradiating the PTFE resin laminated plate with radiation and annealing it. It is possible to improve the handleability and drilling workability during the machining process, which is a problem of the PTFE resin laminate used in the manufacturing process, and the through-hole reliability.

Claims (4)

A method for producing a PTFE resin laminate, comprising irradiating a laminate obtained by laminating a plurality of PTFE resin prepregs and heating and pressurizing them, followed by annealing treatment. The method for producing a PTFE resin laminate according to claim 1, wherein a copper foil is laminated on the outer layer of the plurality of PTFE resin prepregs. The method for producing a PTFE resin laminate according to claim 1, wherein γ rays are used as the radiation. The PTFE resin laminated board obtained by the manufacturing method of Claims 1-3.