PCBA Processing In The Phenomenon Of Poor Wetting And Solutions

- Oct 31, 2017 -

In the pcba processing, when the solder surface tension is destroyed, it will cause the surface mount components of the poor welding. The following technician gave you a look at the wetting of the pcba processing and the production of the monument and its analysis.

1. Poor wetting

Phenomenon: During the welding process, there is no reaction between the substrate weld and the solder after the infiltrated metal, PCBA resulting in less welding or missed welding.

Cause Analysis:

(1) the surface of the weld is contaminated, the surface of the weld is stained with flux, or the surface of the patch element generates a metal compound. Will cause poor wetting. Such as silver surface of the sulfide, tin surface oxide and so will produce poor wetting.

(2) When the residual metal in the solder exceeds 0.005%, the degree of flux activity is reduced, and the phenomenon of poor wetting may occur.

(3) wave soldering, the substrate surface gas, but also prone to poor wetting.

solution:

(1) strict implementation of the corresponding welding process;

(2) pcb board and component surface to do a good job cleaning;

(3) select the appropriate solder, PCBA and set a reasonable welding temperature and time.

2. Tombstones

Phenomenon: One end of the component does not touch the pad and tilted upward or has been in contact with the pad.

Cause Analysis:

(1) reflow soldering temperature rise too fast, heating direction is not balanced;

(2) choose the wrong solder paste, PCBA there is no preheating before welding and welding area size selection error;

(3) electronic components of their own shape easy to produce monument;

(4) and solder paste wetting.

solution:

1. Storage and access to electronic components as required;

2. Reasonable development of the temperature of the reflow area;

3. Reducing the surface tension of the component when the solder melts;

4. Reasonable setting of the printing thickness of the solder;

5. Pcb need to warm up to ensure uniform heating when welding.


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