JP2639091B2 - Manufacturing method of small thermistor element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a temperature sensor for home electric appliances, household appliances, medical appliances, automobile appliances, etc., and manufactures a small thermistor element which can be mounted particularly in a small space. It is about the law.

2. Description of the Related Art Conventionally, this type of thermistor element has a structure as shown in FIG. 5 and is manufactured by steps as shown in FIG. That is, the thermistor fired in a block shape
The wafer is cut into a wafer shape with a slicing saw, and the silver paste is baked on both surfaces of the thermistor wafer. Further, as shown in FIG. 5, the thermistor chip 1 manufactured as described above is sandwiched between two lead wires 2 having a wire diameter of about 0.1 to 0.2 mm and immersed in a solder bath. After that, the lead wire 2 and the silver electrode of the thermistor chip 1 were connected by soldering, and then the whole except a part of the lead wire 2 was coated with a resin 3 such as epoxy.

Problems to be Solved by the Invention Such a conventional method has the following problems.

(1) Since the lead wire diameter is as small as about φ0.1 to φ0.2mm, it is difficult to hold the thermistor chip between the two lead wires. The lead wire may move off or move between the lead wires, and stable quality cannot be guaranteed.

(2) As described in (1) above, the process is complicated,
Due to low yield, it cannot be manufactured at low cost.

An object of the present invention is to solve such a problem and to provide an inexpensive small thermistor element that guarantees stable quality and is inexpensive.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to immerse a thermistor wafer having electrodes formed of silver on opposite surfaces thereof on a solder bath, and to immerse the electrodes in the solder bath. After forming the solder layer, the thermistor wafer is cut into a chip shape by a dicing saw, and two lead wires, one end of which is coated with solder, are brought into contact with the solder layers at both ends of the thermistor chip, and pressurized with a heater. It is an object of the present invention to provide a manufacturing method in which after connecting by heating, the whole except a part of the lead wire is coated with a resin material.

According to the configuration of the present invention, a method is used in which a lead wire having one end covered with solder is brought into contact with the thermistor chip on which the solder layer is formed, and the lead wire is connected by pressing and heating with a heater. By this, the lead wire can be securely connected to the electrode surface of the thermistor chip,
An inexpensive element can be manufactured by guaranteeing stable quality and improving the yield.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view of a small thermistor element obtained by the manufacturing method of the present invention, FIG. 2 is a process diagram showing manufacturing steps of the manufacturing method of the present invention, and FIGS. 3 (A) to (D) and FIG. FIGS. 7A to 7D are diagrams showing a state when a lead wire is connected in the same manufacturing method. In the figure, 4 is a thermistor chip, 5 is a silver electrode, 6 is a lead wire, 7 is a solder layer, 8 is a heater, and 9 is a resin.

First, the thermistor fired in a block shape is cut into a wafer shape by a slicing saw, and after baking silver paste on both surfaces of the thermistor wafer, the thermistor wafer having silver electrodes formed on the opposite surfaces is placed in a solder tank. A solder layer was formed on the silver electrode by immersion and cut into a chip shape using a dicing saw. Furthermore, for example, polyurethane 6b having a wire diameter of φ0.2 mm coated at one end with solder 6a
Lead wires 6 made of a copper wire 6c covered with the above are brought into contact with solder layers 7 on both surfaces of a thermistor chip 4 provided with silver electrodes 5 on both surfaces, and the lead wire 6 is weighed at about 100 g by a heater 8 made of, for example, molybdenum. By heating while applying pressure, the solder 6a of the lead wire 6 and the solder layer 7 of the thermistor chip 4 were melted and connected to each other. Here, as shown in FIG. 3 (C), the heating of the heater 8 causes the solder layer 7 of the thermistor chip 4 to move.
The lead 6 is connected to the silver electrode 5 of the thermistor chip 4 by the solder layer 7a formed by melting the solder 6a of the lead 6. Thereafter, the entire surface of the lead wire 6 except for a part thereof was coated with a resin 9 such as an epoxy resin material.

Effects of the Invention As described above, according to the present invention, a lead wire having one end covered with solder is brought into contact with a thermistor chip on which a solder layer is formed, and heating is performed while pressing the lead wire with a heater.
The solder of the lead wire and the solder layer of the thermistor chip fuse with each other and can be reliably connected. In other words, in the conventional example, the thermistor chip was sandwiched between lead wires having a wire diameter of about 0.1 to 0.2 mm, then immersed in a solder bath, and the lead wires were connected. However, the thermistor chip often comes off or moves during solder immersion.However, according to the present invention, the lead wire can be securely connected to the electrode surface of the thermistor chip. Quality assurance,
In addition, it is possible to provide an inexpensive small thermistor element by improving the yield.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a small thermistor element obtained by the manufacturing method according to the present invention, FIG. 2 is a process diagram showing manufacturing steps of the manufacturing method of the present invention, and FIGS. 3 (A) to (D) and FIG. 4 (A) to 4 (D) are views showing a state in which lead wires are connected in the same manufacturing method, FIG. 5 is a sectional view showing a conventional small thermistor element, and FIG. 6 is a manufacturing step of the conventional manufacturing method. FIG. 4 ... thermistor chip, 5 ... silver electrode, 6 ... lead wire, 6a ... solder, 7, 7a ... solder layer, 8 ... heater, 9 ...
…resin.

Claims (1)

(57) [Claims] 1. A thermistor wafer having silver electrodes formed on both opposing surfaces is immersed in a solder bath to form a solder layer on the electrodes, and then the thermistor wafer is cut into a chip shape by a dicing saw. Further, two lead wires, one end of which is covered with solder, are brought into contact with the solder layers on both surfaces of the thermistor chip, and connected by heating and pressing with a heater. A method for manufacturing a small thermistor element characterized by being coded with a material.