Problems that often occur in small can sealing machine products: low partial discharge initial voltage, sparks between lines or breakdown of TV sets, display line output transformers, automobile, motorcycle ignition and other high-voltage electronic products, often due to the sealing process Improper work will lead to partial discharge (corona), sparks or breakdown between wires, because these small can seamers are high-voltage coils whose diameter is very small, generally only 0.02～0.04 mm, between openings The sealing material is not completely saturated, so that the gap between the coils is maintained. Since the gap is much smaller than the dielectric constant of the epoxy resin sealing material, under alternating pressure conditions, a uniform electric field will be generated, leading to partial discharge of the interface, aging of the decomposed material, and insulation breakdown.

From a process point of view, there are two reasons for the gap between the lines:

1) The vacuum seal is not high enough, and the air between the lines cannot be completely eliminated, so that the material cannot be completely impregnated.

2) The preheating temperature before sealing the specimen is not enough, and the viscosity of the filling material of the specimen cannot be reduced quickly, which affects the penetration.

After the mixing and degassing process, vacuum sealing or sealing the manual, the material mixing and degassing temperature is high, the heat curing process after a long period of work or more materials during the application period and the small seamer products cannot enter in time, It will cause the viscosity of the material to increase and affect the coil immersion. The sealing material of thermosetting epoxy resin composite material, the initial temperature is high, the viscosity is small, and as time goes by, the viscosity increases more rapidly. In order to make the material of the coil have good impregnation, the operation should pay attention to the following points:

1) The sealing material composite should be kept within the given temperature range, under appropriate circumstances, after use.

2) The sample before sealing is heated to the required temperature, and the sealing should be completed in the heat curing process.

3) Vacuum sealing meets technical specifications.

(2) The shrinkage of the sealing surface, partial depression, and cracks. The sealing material will shrink during the thermal curing process, that is, the physical shrinkage of the phase change of the chemical shrinkage from the liquid to the solid during the cooling process. During the shrinking process, there are two further analysis of the chemical changes during the curing process. The micro-network structure formed by the shrinking phase generated from the chemical cross-linking reaction after the heat sealing is called the pre-cured gel shrinkage. The shrinkage from the gel phase to fully cured is called curing shrinkage. The shrinkage rates of these two processes are not the same. The network structure of the former in the process of entering from a liquid consumes a sudden change in the physical state of reactive groups than the latter, and the volume shrinkage rate is also higher than that of the latter. During the gel pre-curing stage (75°C/3 hours), the curing of epoxy groups disappeared in the later stage (110°C/3 hours). The results of differential thermal analysis Figure 8-4 prove this point. The specimen is 750°C/ The degree of curing reached 53% after 3h.

If we seal the test piece for high-temperature curing, the two stages of the curing process are too close, gel pre-curing and cross-curing almost at the same time, it will not only cause excessive exothermic peaks and damage the parts, but also seal the member tape Huge pressure has come, resulting in small can seaming machine product defects inside and outside. In order to obtain a good part, we must design and formulate the formulation of the sealing material during the curing process, paying attention to the problem of matching the curing speed of the sealing material (ie the gel time of a, b composite) and the curing conditions. The commonly used method of the sewing machine is: the nature and purpose of the sealing material are segmented according to the curing process at different temperatures. The color TV line output transformer sub-sewing machine cures the heat release program and internal parts at different temperatures. The temperature in the curing reaction zone of the pre-cured gel sealing material slowly, gradually releases the heat of reaction, the increase in viscosity of the material and the volume shrinkage proceed gently. In the fluid state, the volume shrinkage performance level of this phase material decreases until the gel, which can completely eliminate the volume shrinkage stress of the phase. After the gel is pre-cured, the curing stage should also be gentle heating. After the curing is completed, the seal should be slowly cooled and the heating equipment should be synchronized to reduce the internal stress distribution in many ways. Adjust the workpiece. The surface of the workpiece should avoid shrinkage, depression or even cracking. .

The curing conditions of the sealing material of the small sealing machine agent, but also with reference to the arrangement of the embedded components, the sufficient degree and the size of the workpiece, the shape, the single sealing ability, etc. The internal sealing sealing part. A large number of single joints and seals to bury fewer components, a proper pre-curing temperature reduction, and prolonged gel time are absolutely necessary.