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The composition of solder wire and common problems

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Update time : 2022-10-12 19:31:43
We produce leaded solder wire and lead-free SNCU solder wire inside is hollow, this The design is to store the flux (rosin), so that the flux can be added evenly when adding solder. The role of the solder wire: to meet the electrical conductivity requirements of components on the circuit and the fixing requirements of components on the PCB board.
Evaluation of tin point quality:
1. Non-standard tin point:
(1) Welding: It seems that it is welded, but it is not welded, mainly because the pads and pins are dirty or the flux and heating time are not enough.
(2) Short circuit: The footed parts are short-circuited by excess solder between the feet and the feet. by the inspector, including residual Tin dross shorts pin to pin
(3) Offset: The pins are not in the specified pad area due to the inaccurate positioning of the device before welding, or mistakes made during welding
(4) Less tin: Less tin means that the tin point is too thin to fully cover the copper skin of the part, which affects the connection and fixation.
(5) Multi-tin: The foot of the part is completely covered with tin, and the outer arc is formed, so that the shape of the part and the position of the pad cannot be seen, and it is impossible to determine whether the part and the pad are well tinned.
(6) Wrong parts: If the specifications or types of parts placed are inconsistent with the operation regulations or BOM and ECN, it is a wrong part.
(7) Missing parts: The position where the parts should be placed is vacant due to abnormal reasons.
(8) Solder balls and tin slag: Excess solder balls and tin slag adhere to the surface of the PCB board, which will lead to short-circuiting of small pins.
(9) Polarity reversed: The correctness of the polarity orientation is inconsistent with the processing requirements, that is, the polarity is wrong.
3. Possible causes of bad solder joints:
(1) A tin ball is formed, and the tin cannot be spread to the entire pad: the temperature of the soldering iron is too low, or the tip of the soldering iron is too small; the pad is oxidized.
(2) A tin tip is formed when the soldering iron is removed:
The soldering iron is not hot enough, the flux is not melted, and it does not work. The temperature of the soldering iron tip is too high, the flux volatilizes, and the soldering time is too long.
(3) The tin surface is not smooth and wrinkled: the temperature of the soldering iron is too high and the soldering time is too long.
(4) The rosin is spread over a large area: the tip of the soldering iron is held too flat.
(5) Tin beads: The tin wire is added directly from the soldering iron tip, too much tin is added, the soldering iron tip is oxidized, and the soldering iron is beaten.
(6) PCB layer separation: The temperature of the soldering iron is too high, and the tip of the soldering iron touches the board.
(7) Black rosin: The temperature of the soldering iron is too high.
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