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Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

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Vacuum sintering process curve

The vacuum sintering process curve has a direct impact on the sintering quality. In order to ensure a good sintering effect, an appropriate preheating temperature should be selected and sufficient preheating should be carried out. At the same time, an appropriate sintering temperature and time should be selected to avoid insufficient temperature leading to insufficient reaction or too long time leading to overreaction and excessive temperature leading to 183 ℃ solder melting and other situations occur. The timing of vacuuming is also very important. Since flux is used in the process, the flux needs to be fully extracted during the sintering process to ensure the sintering void rate. Therefore, the vacuum sintering process of low-temperature solder needs to change the traditional programming ideas.

The traditional vacuum sintering curve is shown in Figure 1. Two vacuum-nitrogen cycles are performed at room temperature to exchange the atmosphere, and then the temperature is raised under vacuum. This process is mainly to prevent the oxidation of the solder; when the temperature rises to the highest point When the solder is in a molten state, a little nitrogen (between 60 Torr and 150 Torr) is filled in for heat conduction to melt the solder. When the solder is in a molten state, vacuuming is started to extract the bubbles in the solder, and then the temperature begins to cool down and enter the cooling zone.

Figure 1 Traditional vacuum sintering process curve

The vacuum sintering program curve of 154°C low-temperature solder is shown in Figure 2. After two air exchanges, the temperature is raised under normal pressure. The reason is that the indium-lead-silver low-temperature boxing process is mainly used in component products, and many products have cavities on the back. , the vacuum state heats up very slowly, and gas-assisted heating can be achieved under normal pressure, and the presence of flux will not cause oxidation of the solder; start vacuuming before the solder melts, because the flux is difficult to extract when the solder melts; then enter the air and wait for the solder Melt, and then perform three cycles of vacuuming and nitrogen filling after melting, so that large bubbles can be blown away to ensure the sintering void rate.

Figure 2 Vacuum sintering process curve of 154℃ low temperature solder

This program can also realize rapid program debugging of component products, and quickly realize the production of multiple varieties and small batches of products with obvious characteristics. Control the maximum temperature of the program at 185-190 ℃ to ensure that the Pb63Sn37 (183 ℃) solder will not melt. When adjusting the program for new products, place the temperature measuring thermocouple of the vacuum sintering furnace on the surface of the box to monitor the box temperature. , by extending the highest temperature air intake time to melt the solder, and the final sintering procedure can be determined after one furnace test.