Causes and solutions of virtual welding in SMT processing

Today author from QiHe smt pick and place machine sharing you with Causes and solutions of virtual welding in SMT processing

a. The pad design is flawed.
The presence of through holes in the pad is a major disadvantage of PCB design.
Don’t use it unless you can’t,
Through holes will cause solder loss to form a lack of solder;
Pad spacing and area also need standard matching,
Otherwise, the design should be corrected as soon as possible.

b. The PCB board has oxidation phenomenon, that is, the pad is black and not bright.
If there is oxidation, you can use an eraser to remove the oxide layer to make it shine again.
If the PCB board is damp, it can be dried in a drying box if suspected.
The PCB board has oil stains, sweat stains and other pollution,
At this time, it should be cleaned with absolute ethanol.

c. PCB with solder paste printed, the solder paste is scratched, rubbed,
Make the amount of solder paste on the relevant pad less, make the solder starved.
It should be replenished in time.
The way to make up can be made up with a glue dispenser or with a bamboo stick.
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d. SMD (Surface Mount Components) are of poor quality, expired, oxidized, deformed, and form a virtual solder joint.
This is the more common reason.

1. The oxidized components are black and not bright. The melting point of oxides increases,
   At this moment, it can be welded with more than 300 degrees of electric ferrochrome and rosin-type flux,
   However, it is difficult to melt with SMT reflow soldering at more than 200 degrees and the use of less corrosive no-clean solder paste.
   Therefore, the oxidized SMD is not suitable for reflow soldering.
   When buying components, be sure to check whether there is oxidation.
   And use it in time after you buy it back.
   Similarly, oxidized solder paste cannot be used.
2. Surface mount components with multiple legs,
   its legs are slender,
   It is easily deformed under the effect of external force,
   Once deformed, there will definitely be a phenomenon of virtual welding or lack of welding.
   Therefore, it is necessary to carefully check and repair in time after welding before pasting.

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