The solder bead is formed during reflow soldering, and the outgassing in the preheating process causes part of the solder paste to be squeezed to the bottom of the component body. When the solder is soldered, the isolated solder paste melts out from the bottom of the component and condenses into a solder. Beads. Tin beads generally occur at non-solder points around the chip component body, and 1 to 2 solder beads of larger size are adhered.
For the production of tin beads, the countermeasures given by our company (smt processing) have the following points:
(1) In terms of design, the screen ink between the pads is blocked or the copper between the pads is removed (this process is widely used in SONY products)
(2) Production site
(1) Reduce the preheating rate
(2) Use high metal content solder paste
(3) The stencil is removed from the ship or the solder paste on the inside of the pad is covered.
There is no big difference in the meaning of the Chinese characters of tin balls and tin beads, but in the field of electronic assembly, they are given different meanings: tin balls refer to small and large tin beads, while tin beads refer to large and small sizes. Tin beads phenomenon. The reason for this is because they have different mechanisms.
The above is the sharing of the pcb assembly factory. For more information, please collect the website.
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