Technetters,

I have been having a problem with a PLCC 68, manufactured by Motorola, where about 1 out of 100 components have 1 corner lead bent upwards creating no solder joint.  It's usually pin 9 or 61.  I use a DEK 265 Infinity, laser cut 6 mil stencil, and no clean solder paste.  The feedback from Motorola is that the lead they measured from one defect was within their coplanarity specification of .004".  They suggested using a 7 mil stencil, which I tried with no different result.   I also tried increasing the Z distance, to push the component into the paste more, but I don't think there was much of an impact.  It seems like it would be very difficult to push this many leads further into the paste.  Theoretically, with a 7 mil paste deposit, and if the component went half way down, then I would only have .0035" of allowance for coplanarity, which would not suffice for the tolerance of this component, rig! ht?  

My next plan is to overprint the solder paste 20% longer than the pad (.08" x .025"), and use no reduction of the width (I normally use 10% reduction), with the hope that the reflowed solder would "bridge" the gap.  I am hoping this will work, but does anyone have another suggestion?  Do you think its possible to push the component further into the paste?  A step stencil is impossible because of the density, and there is nothing on the PCB with a finer pitch than this component.  Thanks in advance for your help.

Howard Watson
SMT Manufacturing Engineer
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