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SMT processing defects and quality problems
May 17, 2018



SMT processing defects and quality problems

SMT patch inductor.png

First, the shortcomings of SMT processing


1, connection technology issues

Thermal stress during reflow is the change in temperature at the time of reflow, and the thermal stress caused by the element's inability to fully expand and contract due to external constraints and mutual restraint between internal parts. The body of the part during soldering is directly subjected to thermal stress during soldering, and there is a risk of heating several times.


Thermal Stress:

When the temperature changes, the external stress of the object and the mutual restraint between the internal parts make the stress which cannot be completely freely expanded and contracted, which is also called the temperature change stress.


2, reliability issues

The electrode material and the solder are fixed when the PCB pad is assembled, and the bias of the buffer PCB pad without the lead is directly added to the part body or the solder joint part, so the pressure due to the difference in the solder amount causes the part body to fracture.

 

3, PCB pad test and rework

As SMT integration becomes more and more high, PCB pad testing becomes more and more difficult, the position of needles is getting less and less, and the cost of test equipment and rework equipment is definitely not a small amount.


Second, SMT patch processing quality risks

SMT patch processing quality must pay attention to the following issues:

 

1. Capacitance missing parts (impact parts) will not affect the function at all, only affect the life and effect;

2, BGA welding quality can not be directly observed (bubbles, no melting, offset, etc.);

3, micro-short circuit caused by circuit failure;

4. ESD causes damage to the life of electronic components or functional degradation;

5, IC / BGA caused by poor function or potential poor.


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