FPCWAY

Application of magnetic pulse welding technique

for FPCBs lap joints_4_ Experimental Summary 

5.  Summary and conclusions

in this work, MPW process was investigated for FPCB lap-joint application in two cases: (1) with Al driver; (2) without Al driver and the main results are summarized a follows:

. FPCB sheet can be successfully welded in both cases and the opti- mum bank energy for reliable bonding was about 1.0–1.1 kJ.

. The welded area in FPCB lap-joint has concentrated into two lines with 0.6 mm wideness along of middle part of coil.

. The welded zone has a good joint quality without any damage or heat affect in polyimide substrates of FPCB.

. The deformation of lap-joint is also small for welded samples using Al driver sheet.

. The maximum tensile shearing was obtained around 110–140 N for successful welded samples for both cases and it was nearly same as tensile shearing strength of copper layer of FPCB sheet

. The gap distance between FPCB sheets before welding has very important effect on welding quality and its optimum was 0.4 mm.

. The optical microscope and SIM images of the welded area also show that transition layer was formed without any significant heat-affected  zone  (HAZ).  But  the  wavy  transition  layer  was formed only for samples which were made by using Al driver sheet and this wavy structure was not clear for lap-joint samples without using Al driver sheet.

. Application of MPW process without using driver sheet may be restricted to a particular type ofFPCB sheet because ofmany lim- itations for adjusting eddy current, magnetic pressure and skin depth in very thin copper layer ofFPCB sheet. It can be conclude this case is more applicable for FPCB sheets with thicker copper layer.