PCBA for non-contact infrared thermometer

How to solve the problem of two or more solder joints are connected by tin in SMT

May 07 , 2021

Product quality has become the lifeblood of business survival. In the SMT assembly line, after the PCB passes through the placement machine, it is about to face the heating and soldering forming of reflow soldering. Generally, after reflow soldering, AOI testing is required. If the IC is not well controlled, there will usually be undesirable conditions such as two or more solder joints are connected by tin, so how can we improve it?
We need to confirm whether two or more solder joints are connected by tin before the furnace or after the furnace. If two or more solder joints are connected by tin may have occurred during printing before the furnace, then we need to check the printing machine. If it is a printing machine problem, then we should follow the above Make adjustments. If two or more solder joints are connected by tin after the furnace, adjust the furnace temperature curve. Make more improvements in the reflow time and temperature, as well as the rising slope and warm-up time.


Items NO.

Cause

Improve strategy

1

The stencil is too thick and the amount of solder paste is too much

Use thin steel mesh

2

The distance between the stencil and PCB is too large

Adjust the parameters of the solder paste printer

3

Printing squeegee pressure is too small

Adjust the squeegee pressure of the solder paste printer

4

Multiple printing

Only print solder paste once

5

Solder paste collapses (low viscosity)

Shorten the placement time after printing (adjust the viscosity of the solder paste)

6

Offset in solder paste printing

Adjust the parameters of the solder paste printer

7

The offset of the part placement

Adjust the coordinates of the placement machine

8

The preheating temperature of the reflow oven is too high

Adjust the reflow oven settings


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