1, SMT component solderability is poor, generally for the component welding side oxidation or contamination.

Replace the components (fundamentally solve the problem) or use nitrogen to reduce the possibility of component oxidation at high temperatures in the furnace.

2, SMTpad wetting enough.

Adjust the reflow profile so that the flux is sufficient to clean the PCB's PAD and allow the SMT PCB to warm up fully.

3, the temperature curve set or track speed set incorrect (return temperature curve is appropriate? Warm-up time is too long or the return temperature is too low

In fact, also refers to the temperature curve setting problem, in each temperature zone temperature, time problems, adjust the curve.

4, SMT PCB wiring is unreasonable, there are holes around the pad, making tin into the hole, resulting in less tin or open.

Change the SMT design (once Yong Yi) or the individual screen openings to enlarge, increase the amount of solder (which may be part of the effective)

5, SMTsolder paste is invalid, SMT composition, batch number, access is controlled?

Solder paste failure is mainly refers to the solder paste in the volatile, the content is not enough, can not play in the reflow SMT PCB PAD and welding function.

   The use of solder paste is to be strictly controlled, must be properly stored (4-6 degrees for reference only), remove the use of, must go through a sufficient temperature return time (8-12 hours for reference only), making the flux chemical Activity was restored.

6, solder paste printing release effect is good? SMT Solder paste height is controlled? Whether there is leakage, less tin?

Mainly to see whether all have SMT PAD have a reasonable amount of solder paste, the above example can be used to see the naked eye, the reasonable adjustment PRINTER parameters, reasonable operation PRINTER can solve the above problems.

7, reflow furnace is faulty? Is enough clean? Exhaustions enough?

You can use the equipment to check the machine to get the parameters of each device, especially the temperature and flow. If the flow is insufficient, it will affect the effect of PCB heating. The cleaning problem is in the furnace SMT PCB, PARTS is contaminated, affecting the solderability.

8, the accuracy of the patch has the problem? Is the pressure is too small, too big?

The precision problem is to make the patch offset, in the reflow, the components and pads on both sides of the SMT solder contact surface tension, resulting in one end of the component was pulled up, serious is the tombstone defects.

The pressure is too small, so that the welding end of the SMT components and solder paste is not fully exposed to the same time when the reflow caused by solder infiltration with the time difference, one end was pulled up.

The pressure is too large, so that the solder paste is squeezed out of the pad, not only will cause less solder, but also cause short circuit, tin beads and other issues.

9, SMT PCB pad surface is oxidized, clean enough? Dryness enough? Brass plate? Surface spray FLUX is damaged?