First, how to choose the solder paste to plant the ballThe final result of scraping solder paste to plant balls is basically the same as that of directly using solder balls to plant balls, so for all types of solder balls, can we use both methods? No, according to different situations, we adopt better methods, so as to achieve better results. In general, when the diameter of the solder ball is greater than 0.25 mm, the method of direct ball planting is used, and when the diameter of the ball is equal to or less than 0.25 mm, we adopt the method of scraping solder paste to form the ball.As we all know, the smaller the ball diameter, the higher the requirements for our ball planting process, and the greater the difficulty. Friends who have planted balls know that tin balls less than 0.25 are not active on the ball planting table and have poor mobility. Small size, small weight, easy to be adsorbed. And to ensure that the surface of the steel mesh and the mesh are clean to a considerable extent, a little bit of flux will stick to many solder balls. Then in this difficulty, for a sphere with a diameter less than 0.For 25mm ball planting, we usually use the method of scraping solder paste. II. Precautions for solder paste scraping and ball planting1. The viscosity of solder paste is moderate, and the viscosity is a main parameter. If the solder paste viscosity is too small, that is, too thin, it will cause too much solder paste to be scraped down, which will lead to the situation of even tin. If it is too thick, there may be a gap between the solder paste and the pad.2. The thickness and aperture of the steel mesh should also be moderate. If the steel mesh is too thick or the aperture is too small, there may be a gap between the solder paste and the pad. This is obvious. If the steel mesh is too thin and the amount of tin is too small, it will be harmful to re-welding.3. Reduce the repeated scraping of tin as much as possible to avoid the tin paste in the mesh being squeezed and entering the pad too much, resulting in tin connection.4. A certain temperature should be ensured for later heating, whether it is a ball preheating table or a direct heating with an air gun.
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