First, how to choose scraping paste planting ball
The final result of scraping paste planting balls is basically the same as that of planting balls directly with tin balls. So for all types of tin balls, can we use both methods? No, according to different situations, we take better methods, so as to get better results. In general, when the diameter of the tin ball is greater than 0.25mm, the method of directly planting the ball is used, and the diameter of the ball is equal to or less than 0.25mm. We adopt the method of scraping the tin paste into the ball. As we all know, the smaller the ball diameter, the higher the requirements for our ball planting technology, the more difficult it is. Friends who have planted the ball know that less than 0.25 tin ball is not active on the planting table, and the fluidity is very poor. Small size, small weight, easy to be adsorbed. And to ensure that the surface of the steel mesh, and a considerable degree of mesh clean, a little bit of flux will be associated with many tin balls. So in this difficulty, for ball diameter less than 0.25mm planting ball, we generally use the way of scraping paste.
Two, scraping paste planting ball should pay attention to
1, the solder paste viscosity is moderate, viscosity is a main parameter. The viscosity of the solder paste is too small, that is, it is too thin, it will lead to too much solder paste scraped down, and lead to the situation of even tin. And too thick may solder paste and pad gap.
2, the thickness and aperture of the steel mesh should also be moderate. 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 very obvious, the steel mesh is too thin, the amount of tin is too little, and it will be unfavorable to welding again.
3, as far as possible to reduce repeated scraping tin, avoid the solder paste in the mesh is squeezed and too much into the pad, resulting in even tin.
4, late heating is to use planting ball preheating table or direct heating with wind gun, to ensure a certain temperature.
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