JPS5848407A - Method of producing positive temperature coefficient porcelain semiconductor - 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 The present invention relates to a method for manufacturing a positive characteristic ceramic semiconductor. Conventionally, a cover electrode is formed on a positive characteristic ceramic semiconductor by coating and baking a paste containing metal powder on the surface of an ohmic electrode using an electroless plating method. It is.

When this semiconductor is used as a heating device, a method has been proposed in which a heat conductive sheet is interposed between the semiconductor and the metal substrate in order to effectively transfer the heat of the semiconductor to the metal substrate.

This sheet is generally known to be a mixture of elastic synthetic resin and metal powder. .

However, conventional sheets are cumbersome to manufacture;
, and there is no adhesion between the metal substrate and the semiconductor.
Due to its structure, the seat position can easily shift during assembly.
Therefore, it has very poor assemblability.

Therefore, in view of the above points, the present invention uses Gutufite V-) (hereinafter referred to as Gutufite V-F) as a heat conductive sheet, and after applying the above P; L) to the surface of the semiconductor. The above-mentioned problems are attempted to be solved by bonding the cover electrode and the graphite sheet together by adhering a graphite sheet to the surface and then baking the cover electrode.

The present invention will be explained in detail below with reference to a specific embodiment shown in FIG. In the method of the present invention, first, Tie, BaC0,, PbO,8i0□ is prepared by a conventionally known method.

Y, 0. A barium titanate-based positive characteristic ceramic semiconductor 1 is obtained by mixing and firing the above semiconductors. This semiconductor 1 has, for example, a disk-like shape. The semiconductor 1 has a single Curie point where the resistance value increases rapidly at a specific temperature.

Next, both sides of the semiconductor 1 are polished by a known method, and ohmic electrodes 2 made of Ni are formed on the polished surfaces by electroless plating. Thereafter, the surface of this ohmic electrode 20 is coated with a paste containing a known mug powder.
Printed on an 800 mesh screen. Graphite S with a thickness of 0.1 to 0.5 fl is immediately applied to the surface of this paste before it dries sufficiently and hardens.
/-) 4 is adhered by the adhesive force of the paste itself, and then the whole is fired at a temperature of 150°C to 500°C to bake the above-mentioned paste.

As a result, the paste becomes the cover electrode 3, and the graphite sheet 4 is integrally bonded to the electrode 3, and does not peel off.

Note that a metal substrate 6 is provided on the top surface of this graphite sheet.
is attached, and the semiconductor 1 is crimped onto the substrate 6 using a spring or the like through this graphite sheet.

As described above, in the present invention, since the graphite sheet 4 is integrally combined with the cover electrode 8, the graphite sheet 4 does not shift when the semiconductor 1 is assembled to the metal substrate 5 as described above, and the assembly Workability is greatly improved. In addition, since the cover electrode 8 and the graphite sheet are bonded together using the baking process of the cover electrode 8 instead of using adhesive, bonding the graphite sheet is very easy. be.

Next, experimental results are shown in figures gg to s.

FIG. 8 shows the influence of the mesh size of the screen used in the Ag paste screen FIIilJ on the electric power applied to the gasoline mixture. The electric power applied to the gasoline mixture (hereinafter referred to as electric power) is the electric power consumed by the semiconductor 1 when a gasoline mixture at a constant temperature and a constant flow rate is applied to the surface of the metal substrate 50 in the nineteenth configuration. If the mesh size is more than 300 meshes, the thickness of the Ag paste will not be sufficient, and the graph eye sheet will not adhere well and the power will decrease. On the other hand, if it is less than 150 meshes, the thickness of the Ag paste is too thick, resulting in poor thermal conductivity and reduced power.

Figure 8 shows the influence of the dimensional difference between the semiconductor l and the graph eye (sheet) on short circuits. /total number. If dimension 6 in FIG. 3 (dimension between the outer edge of semiconductor 1 and the outer edge of semiconductor 4) is smaller than 0.6, shimmy 1 occurs.

Figure 4 shows the effect of graphite thickness on power. The thickness of graphite sheet 4 is 0.1III
If it is thinner than I, it will not be able to sufficiently follow the surface roughness and strain of the semiconductor I and metal substrate 5, resulting in a decrease in power. Also, Q
If it is thicker than Jlg, the thermal conductivity will deteriorate and the power will decrease.

FIG. 5 shows the effect of baking temperature of Ag paste on power. If the baking temperature is higher than 650°C, the graphite carbon will decompose, resulting in poor thermal conductivity and reduced power.

In addition, there is no material that can be used for mug paste, which can be baked at a baking temperature lower than 150°C.

Next, a heating device employing a semiconductor obtained by the method of the present invention is shown in FIGS. 6.7 and 8.

FIG. 6 shows a structure in which a semiconductor 1 is housed between a metal substrate 5 and a bottom plate 8, and 7 in the figure is a spring. The collar is fixed, for example, to the riser wall of the intake pipe of an internal combustion engine, and is used as a riser heater.

7' and 8 show a structure in which a semiconductor 1 is arranged between cylinders 5 and 9, a positive electrode plate 6 and an insulating material 8 are arranged, and the semiconductor 1 is pressed by a plurality of U-shaped springs 7. It is. This is arranged, for example, between the carburetor and the intake pipe of an internal combustion engine, and allows the fuel mixture to flow inside the cylinder 5.

In the present invention, the graphite sheet absorbs the strain and surface roughness of the semiconductor 1 and the metal substrate 5 with its elastic force, improving adhesion and exhibiting extremely good heat transfer characteristics. Graphite Sea No. 1 also has excellent electrical conductivity.

Figure 9 shows the effect. 1 shows an example of the present invention, 1 shows an example in which a semiconductor and a metal substrate were polished and the two were directly bonded, and C shows an example in which the two were directly pressure bonded without polishing.

In addition, in the present invention, the material of the electrode 2.8 is not limited to the above-mentioned embodiments, and any material may be used.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a button device using a semiconductor obtained according to the present invention, and FIGS. 2 to 6 are characteristic diagrams for explaining the present invention.
6 and 7 are cross-sectional views showing a heating device ffl using a semiconductor that has been completely obtained. FIG. 8 is an enlarged cross-sectional view of section A in FIG. 7, and FIG. FIG. l...Semiconductor, 2.8...Electrode, 4...-Graph eye sheet. Representative Patent Attorney Takashi Okabe 11 Figure 2 Figure 3 @srj! Figure 9 of Figure 8

Claims (1)

[Claims] Electrodes are formed on the surface of a PTC ceramic semiconductor by electroless plating, and a paste containing metal powder is applied and baked on the surface to form a cover electrode. A method of manufacturing a PTC porcelain semiconductor, which comprises bonding the sheet to a housing cloth surface and then baking it to integrally bond the sheet to the cover electrode.