JPH0313993Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a lead wire mounting structure in a ceramic heater.

In a conventional ceramic heater, as illustrated in FIGS. 1 and 2, a heating resistor pattern 2 is embedded in a ceramic body 1 such as alumina ceramic, and both ends of the heating resistor pattern 2 are exposed at exposed ends. 3 is plated with nickel, and a lead wire 4 made of a metal such as Kovar, 42 alloy, or nickel, which has a coefficient of thermal expansion similar to that of silver solder, is soldered to the lead wire 4. Therefore, since the heating resistor pattern 2 is buried in the ceramic body 1 and isolated from the outside air, there is less risk of deterioration or disconnection of the heating resistor pattern due to corrosive gas or oxidation, and the temperature rises quickly. 2 is mainly formed from metal powders such as tungsten, molybdenum, and manganese, and has a positive temperature resistance coefficient, and has features such as a self-temperature adjustment function that does not rise above a certain temperature. , is widely used in various fields.

However, despite having such advantages, nickel wire, which is most commonly used as the lead wire 4 that is soldered to the exposed end 3 of the heating resistor pattern 2, is made of ceramic, silver solder, Since the coefficients of thermal expansion of nickel metal are not completely the same, thermal stress based on the difference in thermal expansion acts repeatedly,
In addition, since the soldering part of the lead wire 4 is continuously heated to about several hundred degrees, the atmosphere in which the ceramic heater is used may be oxidized by oxygen in the air, or silver solder may be oxidized by sulfide gas in an oil burner, for example. This makes it vulnerable. When the above factors combine and vibration or external force acts on the lead wire 4 soldered to the exposed end 3 of the heat generating resistor pattern 2, the lead wire 4 will peel off, causing damage to the heat generating resistor pattern 2 and the ceramic body. 1 had a situation where it did not function as a heater even though there was no abnormality.

The present invention is a ceramic heater developed in view of the above situation, and is particularly intended to avoid a decrease in the mounting strength of the lead wires.

Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings. Note that parts that are the same as before are given the same symbols.

FIG. 3A is a partial sectional view of a ceramic heater according to an embodiment of the present invention. This ceramic heater has a heating resistor pattern 2 embedded in a ceramic body 1. A recess 7 is formed in a part of the ceramic body 1, and the heating resistor pattern 2 is exposed at the bottom of the recess 7. After nickel plating 3, the lead wire 4 is soldered using silver solder, and a glass material is filled in the recess 7 and welded to cover the soldered part and the end of the lead wire 4. It has a structure in which layer 5 is applied.

In addition, as in the embodiment shown in FIG. Alternatively, a concave portion 7 may be formed, a lead wire 4 is soldered to the exposed end portion 3, and a glass material is filled in the concave portion 7 to form a vitreous layer 5.

As described above, in the ceramic heater of the present invention, the exposed end portion 3 of the heating resistor pattern 2 and the lead wire 4 are brazed together in the recess 7, and the recess 7 is filled with a glass material to form the vitreous layer 5. Since the vitreous layer 5 is formed, there is no fear that the vitreous layer 5 will peel off, and a strong bonding structure can be achieved.

Next, 20 samples were manufactured under the same conditions, such as the lead wire brazing structure shown in Figure 2 B, the lead wire diameter was 1 mm, and the same amount of brazing material. For 10 pieces, a glass material having a melting point of about 500° C. was used to form a vitreous layer about 1 mm thick, as in the example shown in FIG. 3A. A total of 20 samples, 10 with the glassy layer attached and 10 unattached with the solder, were repeatedly heated intermittently at 300℃ under the same atmosphere. After 500 hours, when an external force was applied to each lead wire in the same direction, all but one of the 10 lead wires remained in solder contact but did not have a glassy layer attached. It peeled off from me. On the other hand, the 10 samples coated with the glassy layer showed no abnormality at all, and even after repeated heating experiments for 5000 hours, not a single sample peeled off from the solder joint.
No deterioration in strength of the brazed joint was observed at all.

This is thought to be due to the fact that the glass layer prevents external force or stress from the lead wire from acting on the solder joint, and also because of the pressure bonding effect of the glass layer.

As described above, the present invention has a structure in which the solder joints of the ceramic heater lead wires and the vicinity of the solder joints of the lead wires attached in solder contact are covered with a glassy layer, and the ceramic body, the brazing material, It avoids thermal stress due to the difference in thermal expansion between the lead wire materials and external forces acting on the lead wire, and the dense glass layer blocks harmful gases such as sulfide gas and prevents deterioration of the brazing material. It is possible to provide a ceramic heater that does not cause a decrease in the strength of the wire soldering portion.

[Brief explanation of the drawing]

Figures 1A and 2B and Figure 2A and 2B are plan views showing the solder connection of lead wires of conventional ceramic heaters, and
- It is a figure which shows each X-ray cross-sectional view. FIGS. 3A and 3B are partial cross-sectional views showing the lead wire soldering portion of the ceramic heater according to the embodiment of the present invention. 1: Ceramic body, 2: Heat generating resistor pattern,
3: exposed end, 4: lead wire, 5: glassy layer.

Claims (1)

[Scope of utility model registration request] In a ceramic heater having a heat generating resistor pattern embedded in a ceramic body, a recess is formed by drilling the ceramic body or by attaching a frame, and the heat generating resistor pattern is exposed at the bottom of the recess. A ceramic heater in which a lead wire is soldered to the exposed end of the ceramic heater, and a glass material is filled in the recess so as to cover the surface of the soldered part and the end of the lead wire.