Many thermal silicone pad manufacturers will inevitably encounter problems of one kind or another in the process of producing thermal silicone pad. One of the problems that plagues thermal silicone pad manufacturers is that the thermal silicone pad foams during the production process. Once the thermal silicone pad foams, it will be regarded as a defective product and thrown away without recycling or any other value, which directly increases the defect rate to the thermal silicone pad manufacturer and causes cost pressure. Then, Nuofeng Electronics analyzes the reasons and solutions for the foaming of thermal silicone pad.
There are many reasons for blistering in the production process of thermal silicone pad, which are mainly as follows:
- The vulcanization temperature is too low: the vulcanization temperature is an important parameter affecting the molding of silicone rubber. Usually the thermal silicone pads is set at 160~200℃, but sometimes the mold is too long due to the long operation time of the mold or other reasons. The temperature of the silicone molding mold is low, and there is a temperature difference with the vulcanization temperature of the silicone, which will cause the silicone product to foam after molding. In this regard, we only need to increase the molding temperature, or open the empty mold into the machine for a period of time and then operate to solve the problem.
- The vulcanization temperature is too high: The first point is that the vulcanization temperature is too low, which will cause the thermal conductive silicone to foam. In fact, in many cases, the molding temperature is too high. Why? When the molding temperature is too high, the silica gel material on the surface has already begun to be formed during the mold clamping and pressurization process. At this time, the air has been trapped inside and it is difficult to discharge, so it will cause molding bubbles. For this reason, it is only necessary to appropriately lower the molding temperature.
- Insufficient exhaust: After the silicone raw material is placed in the forming mold, a lot of air will be brought in at the moment of closing the mold, and it is impossible for the air to be integrated with the thermal conductive silicone material. If the air is not discharged, it will cause After the silicone is molded, air bubbles are formed on the surface.
- The structure of the mold is unreasonable: the unreasonable design of the silicone molding mold will also cause bubbles in the molding of thermally conductive silicone. For example, the arrangement of the products in the mold, the partition method, the mold parting method, and the design of the mold size will cause poor foaming. , but the cost of opening a set of molds is very high, and it is not easy to modify. If the silicone molding foams due to the structure of the mold, it is usually solved from the points mentioned above.
- The vulcanization time is too short: Like the vulcanization temperature, the vulcanization time is also one of the important parameters affecting the molding of the thermally conductive silica gel. The length of the vulcanization time determines whether the thermally conductive silica gel can be completely vulcanized. If the curing time is too short, it will not only cause the silicone to become soft after molding, but also more likely to cause surface bubbles. If such defects occur, the curing time of silica gel can be appropriately extended.
- The production process is also very important: the anti-aging agent RD is easy to produce bubbles during the mixing operation of the open mill, which is mainly due to the high melting point of the anti-aging agent RD and the low operating temperature of the open mill. Special attention should be paid to the dispersion of zinc oxide during refining, and the uniformity of its dispersion will also cause the generation of small bubbles, so the silicone rubber mixing process is also a very important part.
- Whether the moisture content of the raw materials used in the formula, the mixing operation and the extruded water vapor of the products, and whether the drying is sufficient after cooling, will also cause bubbles in the molding of the thermally conductive silica gel, which is mainly caused by the evaporation of water during vulcanization.
After the thermal silicone pad is foamed and then attached to the heat source to dissipate heat, it will not only affect the effective contact area of the thermal silicone pad, but also air will enter the bubbles, thereby increasing the thermal resistance. The size of the effective contact area and the size of the thermal resistance are the two main performance parameters to judge the thermal conductivity of a thermal silicone pad except for the thermal conductivity. Therefore, the thermal silicone pad should not be shipped after foaming and must be classified as Defective products.