JPS6235501A - Manufacture of high polymer positive temperature coefficientresistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a polymeric positive temperature characteristic resistor, and more specifically, the present invention relates to a method for manufacturing a polymeric positive temperature characteristic resistor, and more specifically, to The present invention relates to a method for manufacturing a polymer positive temperature characteristic resistor having low contact resistance and high resistance to heat shock.

[Prior art and problems to be solved by the invention] Recently, polymers whose base material is made of a polymer and have positive temperature characteristics have been used as positive temperature characteristics elements used incidentally to electrical and electronic equipment parts. Resistors are used for prizes.

Such a resistor is usually composed of a polymer molded body having positive temperature characteristics and electrodes attached to the front and back surfaces of the polymer molded body.

Some of these polymer resistors include, for example, USP-4428
As disclosed in Japanese Patent Publication No. 1333, metal foils are crimped and integrated as electrodes on the front and back surfaces of a molded body having positive temperature characteristics, and as disclosed in Japanese Patent Application Laid-Open No. 15907-1983. Furthermore, it is known that mesh metals are thermally fused and integrated as electrodes on the front and back surfaces of a molded body having positive temperature characteristics.

However, in such a polymer resistor in which metal foil or mesh metal is attached to a polymer molded body, it is difficult to sufficiently reduce the contact resistance between the electrode and the molded body.

Furthermore, a method is known in which electrodes of a polymeric positive temperature characteristic resistor are formed by applying metal plating to the surface of a molded body (Japanese Patent Laid-Open No. 80-3881).

However, in this case, the adhesion strength between the plating film and the molded body is not sufficient, and heat damage occurs. There is a problem that the resistance to ivy is not sufficient.

The present invention solves the above-mentioned problems and uses a polymeric positive temperature characteristic resistor that has high mutual adhesion strength between an electrode and a molded body having positive temperature characteristics, has low contact resistance, and has high resistance to heat shock. The purpose is to provide manufacturing methods.

[Means and effects for solving the problems] The method for producing a polymeric positive temperature characteristic resistor of the present invention comprises a method of manufacturing a polymeric positive temperature characteristic resistor of the present invention by combining 40 to 80% by weight of a crystalline polymer and 10 to 60% by weight of a conductive filler. A conductor is embedded in a molded body of the cross-wire composition by pressure bonding so that a part of the conductor is exposed from the surface of the molded body, and then the surface of the molded body where a part of the conductor is exposed is plated. It is characterized by being subjected to processing.

First, the molded article having positive temperature characteristics used in the present invention is made of a crystalline high molecular weight polymer and a conductive filler.

Examples of the crystalline polymer, which is one of the constituent elements of the molded article, include polyethylene, polypropylene:ethylene copolymer, polyamide, fluorine-based polymer, and the like.

In addition, as the conductive filler, which is another requirement, carbon black such as furnace black, thermal black, and acetylene black is preferable, and its low particle size is graphite powder of 20 l or less, metal particles: length 111 or less, and aspect ratio. Examples include 10 or more carbon fibers, metal fibers, and mixtures thereof.

A molded article having positive temperature characteristics can be obtained by blending the above-described crystalline polymer and a conductive filler, melt-kneading the mixture, and then molding the mixture by a conventional method.

The mixing ratio of the crystalline polymer and the conductive filler is set to 40 to 90% by weight for the former and 10 to 60% by weight for the latter.

If the amount of the conductive filler is 10% by weight or less (therefore, the crystalline polymer is 90% by weight or more), the resulting molded article will not exhibit positive temperature characteristics; If it exceeds , it becomes difficult to mix lines.

Melt kneading is carried out using a normal melt kneading machine such as a Banbury mixer with 12 rolls or 3 rolls, at a temperature of 120 to 25
0°C for 9 hours: 5 to 40 minutes. Also, during melt mixing, 2,5-dimethyl-2,5-di(t
Crosslinking may be effected by adding a well-known crosslinking agent such as -butylperoxy)hexyne-3.

The main feature of the present invention is that a conductor is crimped onto the molded body obtained as described above, and then a plating process is performed thereon.

The conductor used is a metal such as Ni.

Cu, Fe, A-texture, brass, etc. net-like materials, fine wires, powders.

Examples include flakes, nonwoven fabrics, carbon fiber nonwoven fabrics, and fiber powder.

When the conductor is crimped onto the surface of the molded body, it is necessary to perform the crimping to such an extent that most of the conductor is embedded in the molded body and a portion of the conductor is exposed from the surface of the molded body. If the part of the conductor embedded in the molded body is small, the adhesion strength between the molded body and the conductive body will be weak, and if the conductive body is completely embedded in the molded body, it will not be formed by the plating process described below. It is difficult to obtain contact between the plating film and the conductor, and therefore sufficient adhesion strength between the molded body and the plating film cannot be obtained.

The pressure applied when crimping to the above degree varies depending on the type of conductor used and the composition of the molded body, but is usually 2.
~100kg/ctd -G preferably 5-50 kg
/CrA-G.

In this pressure bonding step, it is necessary to heat the molded article to a temperature higher than the crystallization temperature of the crystalline polymer. If the molded body is not heated above this crystallization temperature, the crimping step of 0 or more, where the adhesion strength between the molded body and the conductor is insufficient, can be carried out using a hot press molding machine or a hot roll molding machine. can.

After the crimping step is completed, the surface of the molded body where a portion of the conductor is exposed is then plated, and as a pretreatment for this plating process, the molded body is subjected to an etching process.

Etching methods include methods using a chromium mixed acid solution, hot paraxylene solution, etc., and methods of mechanically roughening the surface such as sandblasting.

Next, as a plating method for plating the surface of the etched polymer molded body, either an electroplating method or an electroless plating method can be applied.

In the electroplating method, the molded body is immersed in a plating bath containing a metal salt as a cathode, and a metal, graphite, etc. is used as an anode.
OA/dm2. The plating solution is stirred at a plating bath temperature of 10 to 100°C.

In the electroless plating method, after activating the surface of the molded object using the sensitizing activation method or the catalytic accelerator method, which are used in ordinary plastic plating methods, as a pretreatment for plating, It is preferable to perform electroless plating according to the method of electroless plating. Furthermore, after performing electroless plating, electroplating may be further performed in order to obtain a plating film of a predetermined thickness.

In addition, the metals that make up the plating film include nickel,
Copper, tin, chromium, silver, cobalt, etc. are preferred.

Further, it is preferable to adjust the plating treatment time and the amount of electricity so that the thickness of the plating film is 0.1 or more.

[Examples of the invention] Example 1 High-density polyethylene (manufactured by Idemitsu Petrochemical ■: Idemitsu Polyethylene 'I 540B) 100 as a crystalline polymer
Carbon black with an average particle size of 43 mg per part by weight (
After blending 75 parts by weight of Diablack 0E (manufactured by Mitsubishi Chemical Corporation) and melt-kneading this in a Banbury mixer, 2,5-dimethyl-2,5-di(t) was added as a crosslinking agent.
-Butylperoxy)hexyne-3 (1 part by weight) was added and crosslinked to obtain a resin composition. Next, this composition was formed into a sheet with a wall thickness of 1 mm using a hot press machine, and this sheet was made into a 5 cm long sheet.

A test piece with a width of 10 cm was cut out.

A nickel-plated copper mesh (50 meshes) was placed on both sides of the obtained test piece, and it was crimped for 5 minutes at 135°C with a pressure of 10 kg/CrA@G using a hot press molding machine. Processed. As a result, a test piece was obtained in which most of the net was embedded in the sheet and a portion of it was exposed on the sheet surface.

The test piece subjected to the above pressure bonding treatment was immersed in a chromic acid mixed solution (high chromic acid mixed acid) and etched at 60° C. for 10 minutes. Next, after washing the test piece with water, nickel sulfate 29
0g/l, nickel chloride 50g/l, boric acid 40g/l
The specimen was immersed in a plating bath containing an aqueous solution, and electroplated using the test piece as a cathode and the nickel plate as an anode. Electroplating is performed at 42°C with cathodic current density IA
/dm2*Electricity 1θ00 Clone From the nickel-plated piece thus obtained, lc+
A square test piece was taken out, and the electrical resistance between the front and back nickel plating films was measured by the four-terminal method using a digital voltmeter.

As a result, the electrical resistance value at room temperature was 0.08Ω, and the ratio of the resistance value when the temperature was raised to 150°C and the resistance value at room temperature was 4.3Ω (resistance increase magnification) was 10.

In addition, the peel strength of the nickel plating film (JIS-8
854), but the V and adhesion force were too large to measure. Furthermore, when the nickel film was examined for peeling after being subjected to a heat shock from 230°C to 20°C, there was no peeling at all and the result was good.

Example 2 A test piece was produced in the same manner as in Example 1, except that a thin piece of carbon fiber nonwoven fabric was used as the conductor instead of the nickel-plated copper mesh, and the amount of electricity during electroplating was 1200 clones. . As a result, the electrical resistance value between the nickel plating films used for the electrodes was 0.11Ω, and 150Ω.
When the temperature was raised to 4.3°C, the resistance increase factor was 10, and furthermore, at 230°C
The nickel plating film did not peel off even after being subjected to a thermal shock from 20°C to 20°C.

Comparative Example 1 A 1 cm square test piece was taken from Example 1 in which the nickel plating was omitted, and the electrical resistance value between the front and back copper mesh electrodes was measured. As a result, the electrical resistance value is 4
．． It was a large value of 78Ω.

Comparative Example 2 A molded product obtained in Example 1 was prepared in which the same plating treatment as in Example 1 was directly applied to the surface of the molded product without embedding a conductor therein. In this case, the electrical resistance value between the nickel coatings of the Icm square test piece was 0.13Ω, which was good, but the peel strength of the nickel plating coating was 0.18kg/cm.
The plated film was partially peeled off due to heat shock from 230°C to 20°C.

[Effects of the Invention] As explained above, the polymer positive temperature characteristic resistor obtained by the method of the present invention has high mutual adhesion strength between the electrode and the molded body, low contact resistance, and high resistance to heat shock. is large.

Therefore, the manufacturing method of the present invention is effective when applied to manufacturing a positive temperature characteristic resistor 2 heating element used in electrical/electronic equipment and the like.

Claims (1)

[Claims] A conductor is placed in a molded body of a kneaded composition of 40 to 90% by weight of a crystalline polymer and 10 to 60% by weight of a conductive filler so that a part of the conductor is exposed from the surface of the molded body. 1. A method for manufacturing a polymer positive temperature characteristic resistor, which comprises embedding the conductor in a molded body by pressure bonding, and then plating the surface of the molded body where a part of the conductor is exposed.