Method for processing patch diode

Abstract

This invention relates to a processing method for chip diodes, which carries out oil-removing, cleaning and drying chip tube cores and upper and lower leading pin strips, puts the lower leading pin strip into a graphite mould and squeezes the paste solder onto the connection place of the pins, puts the chip tube cores on the solder of the lower leading pin strip, then, puts the upper leading pin strip on the core to close the cover, then puts the graphite into an electric oven to be heated to 350-600deg.C in 20-35min to melt the solder to be lowered to 300+-10deg.C to keep it for 10-15min then to be cooled slowly to the room temperature for 20-25min to take out the mould, puts the pin strips with chip tube cores in the mould to be injected with insulation resin to be sealed and divides the corner cut into chip diodes, bends, then plates and tests the leading pins to be packed.

Description

technical field [0001] The invention relates to a processing method of a diode, in particular to a processing method of a patch diode. Background technique [0002] Since the core area of ​​the chip diode is larger than that of the pillar diode, it has the characteristics of large conduction area and good voltage resistance, and it is more and more used in various printed circuit boards. However, the processing of conventional SMD diodes is to solder and fix the tin solder on the upper and lower connection surfaces of the chip die respectively, put the lower lead strip into the graphite mold, and then put the chip die and the upper lead in turn. After the upper cover of the belt and graphite mold is covered, it is sent into the electric furnace and heated to 360 ° C ~ 400 ° C, the heating time is 30 minutes ~ 45 minutes, the solid solder is heated and melted, and the upper and lower lead belts are welded to the sheet core, and finally the belt with The pin strips of the chi...

AI Technical Summary

Problems solved by technology

At present, the processing method of SMD diodes mainly has the following disadvantages: 1. Large error of conduction area

Since the solder is first welded on the upper and lower connection surfaces of the sheet die, and the solder at room temperature is solid, due to the small friction resistance of the contact surface between the sheet die and the upper and lower pins, the upper lead with In the process of loading the frame and sending the graphite mold into the electric heating furnace, there will inevitably be an offset between the sheet die and the upper and lower pins, which reduces the distance between the sheet die and the leads. The contact area, due to the reduction of the conduction area of ​​the diode, reduces the current flowing through the diode, resulting in easy breakdown of the diode, resulting in a low pass rate and yield rate of the SMD diode, which is also the main reason for the unstable quality of the SMD diode. one

2. The welding strength of the diode is low

Since the tin solder used is solid at room temperature, flux cannot be added, so during the soldering process, the gas generated after the solder is heated cannot be discharged, and the gas will form pores in the weld, so the upper and lower pins There will be a virtual soldering phenomenon between the sheet die and the resulting decrease in soldering strength

In addition, due to the existence of air holes, the contact area between the chip die and the upper and lower pins is also reduced.

At the same time, due to the poor extensibility of the solid solder during the melting process, the solder cannot fill the connection surface between the chip die and the upper and lower pins during the soldering process, and the problem between the pin and the chip die cannot be solved. The problem of unstable contact area between

3. The processing technology is unreasonable

Due to the use of secondary soldering, the solder is first soldered on the upper and lower surfaces of the chip die, and the surface of the solder will be slightly oxidized during the production process. Therefore, in the second soldering, due to the oxide layer on the solder surface, the Cause poor welding, in severe cases, even unable to weld

4. The process is complex

Due to the need for secondary welding, it not only needs to invest in the previous welding tooling, but also increases the labor intensity of the workers, so the production efficiency is not easy to improve