In a flexible printed circuit board (FPC) on the technological requirements of SMD in the miniaturization of electronic products development, quite a number of consumer products, SMT, because the assembly space, the relationship between the SMD on FPC is pasted on the complete machine assembly. FPC on SMD surface-mount has become one of SMT technology development trend. For SMT process requirement and attention points have the following points.
I. regular SMD mounting
Features: low mounting accuracy, small number of components, mostly resistance and capacitance, or a few special components.
1. Solder paste printing :FPC is positioned on the printing plate by its appearance. It is usually printed by a small semi-automatic printer, or manual printing, but the quality of manual printing is worse than that of semi-automatic printing.
2. Mounting: manual mounting can be used in general. For some components with higher position accuracy, manual mounting can also be used.
3. Welding: the re-flow welding process is generally adopted, and spot welding can also be used in special cases.
2. High precision mounting
Features :FPC should be marked with MARK for substrate positioning,FPC itself should be flat.FPC is difficult to be fixed, consistency is difficult to be ensured in mass production, and equipment requirements are high.
1.FPC fixation: the entire process from the printing patch to the backflow welding is fixed on the pallet.Method B is used when the mounting accuracy is less than 0.65mm between leads of QFP.
Method A: the plate is covered on the positioning template.FPC is fixed on the plate with thin high-temperature tape, and the plate is separated from the positioning template for printing.
Method B: the pallet is customized, and the process requirements for the pallet must be subjected to multiple thermal shocks and the deformation is minimal. There is a t-type positioning pin on the pallet, which is slightly higher than FPC.
2. Solder paste printing: because the plate is loaded with FPC and there is high-temperature tape used for positioning on the FPC, the height is inconsistent with the plane of the pallet, so an elastic spatula must be used when printing.