
PN6280_Hardware Design
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The highest temperature can’t too high. In the condition that meet the welding quality of customer
motherboard and module, the lower furnace temperature and the shorter maximum temperature
time, the better.
Some
customer’s temperature curve in the line is not suitable, high temperature is too high, and
customer motherboard melt good, but non-performing rate is on the high side. Through the analysis
of the causes, it found that melt again of BGA components lead device offset and short circuit. After
adjusting the temperature curve, it can
ensure that the customer’s motherboard the welding quality,
and also improve the pass through rate. Non-performing rate is controlled below the 2/10000.
6.2.3 SMT stencil design and the problem of less tin soldering
Part of customers found false welding or circuit short when reflowing. The main reason is module tin
less, PCB distortion or tins too large. Suggestions are as follows:
Suggest use ladder stencil, which means the depth of the region of module is thicker than other
areas. Please adjust validation according to the measured thickness of solder paste, the actual
company conditions and experience value. The products need to strictly test.
Stencil: Reference module package, and the user can adjust according to their company
experience; Outside of the module, the stencil extends outside. The GND pads use the net stencil.
6.2.4 SMT attentions
If customer motherboard is thin and slender with a furnace deformation, warping risks, you will be
suggested to create "a furnace vehicle" to ensure the welding quality. Other production proposals are
as follows:
The solder pastes use brands like Alfa.
The module must use the SMT machine mount (important), and do not recommend manually
placed or manual welding.