FPC soldering Technology

Should adopt mandatory infrared reflow furnace hot air convection, so the temperature on the FPC can evenly changes, which reduce the generation of bad welding.If using a single side tape, because it only fix the four edges of FPC, because in the condition of hot deformation, the middle part of bonding pad tends to tilt, molten tin (under the high temperature of liquid tin) will flow to generate empty welding, soldering, tin beads, make the process defective rate is higher.

1) temperature curve test methods:
    Due to the Heat absorptivity is different to the load Flexible pcb , difference type of components on FPC, the difference of their temperature rising speed after heated during reflow soldering, have different heat absorption, so carefully set reflow furnace temperature curve will bring great influence to welding quality. Relatively reliable method is, according to the plate spacing during actual production, put two sheet of the load board which with FPC in front and behind of the test board, at the same time, the FPC on the load board sticked with components, with high temperature solder wire to weld the test temperature probe onto the test points, at the same time use high temperature resistant tape to fix the probe wire onto the load board. Note that high temperature resistant tape can not cover the test point. Test point should be adopted the solder points which near the load board edges and the QFP pin, in this way the test result can better reflect the real situation.

2）Setting of the temperature curve：
During furnace temperature debugging, because the average warm to FPC is NG, thus it's best to adopt heating/insulation/reflow temperature curve method, so that each area’s parameter is easy to be control led, others, influence of heat shocks to FPC and other components will be smaller. Based on experience, the best temperature will be dispatched to the lower limit of solder paste technical requirements value, wind speed of furnace is generally adopt the minimum wind speed, chain of reflow furnace’s stability should be, can't have.

Conclusion: When doing SMD mounting on FPC, the top importance is to realize accurate positioning and fixation, the key for fixation if to make an appropriate load board, and the second importance is the prebaking, tin printing, mounting and reflow soldering to FPC. Difficulty to FPC soldering is obvious higher than to rigid PCB. so it is necessary to accurately set the process parameters,at the same time, strict production process control is also important, must ensure that operators strictly implement each regulation on SOP, engineer who track the line and IPQC should strengthen the inspection,  Discover the unusual situation of production line in time，with line engineers and IPQC inspection should be strengthened, timely discover the unusual situation of production line, analyze the reason and take the necessary measures so that can control the FPC SMT production line NG rate within scores of PPM.