Control of FPC SMT

Although SMT Technology is mature for rigid Printed circuit board, however, many problem may be faced during FPC SMT.

Because FPC fixed on the mould before SMT, and the FPC with high temperature heat-resistant pressure-sensitive adhesive tapes for purpose of location, which make its planar inconsistencies, thus FPC printing surface is unlikely to be as smooth as rigid PCB and the same consistent on thickness and hardness, so operator should not use a metal scraper, and should use the polyurethane scraper which with hardness of 80-90 degree.

Solder paste printing machine is best to be with the best optical positioning system, otherwise will have great influence to printing quality, FPC although fixed on the load board, however, there always be small space between FPC and the load board, this is the biggest difference as rigid PCB board, thus the equipment parameters’s setting will also has great influence to the printing effect.

Printing stations is also the key location to prevent FPC from being smudgy, need to wear glove then can go ahead for operation, at meanwhile, workstation should be kept clean, stencil should be frequently wiped to be clean, to prevent the solder paste to pollute the gold fingers and gold plated key button.

According to the properties of the products, components quantity and efficiency of mounting, it is OK to adopt high-speed placement machine for SMT.
Because every piece of FPC has positioning with fiducial MARK, therefore, there’s no big difference on surface mounting technology between FPC SMD mounting and rigid PCB SMD mounting. It is important to note that although the FPC are fixed on the load board,

But its surface can’t be the same flatness like rigid PCB board surface, local space must exist between FPC and load board, so, the height of suction nozzle’s dropping, compression of blowing should be exactly settled. On other side, most bare FPC performance as panel format, and the rate of good finished product relatively low, so it if normal that there’re part of pieces with not good quality, which request recognition function on BAD MARK to SMT machine, otherwise, when mounting FPC panel with the status of not all pieces are good, will show low efficiency.

FPC SMT need make to make mould for fixing, mould is expensive compare to SMT price for each PCS, not everyone will accept it. Some small SMT factories are not willing to make FPC assembly even their ability for rigid PCB assembly is good.