I am having problems with skewed placement of 0402 devices I would like to add the board has raised pads and we are placing on glue. We are now printing the glue rather that dispensing with a GL5. have any of you guys had this problem, any info much appreciated
If your pads are raised as you mentioned, you will reach just the tip of your tiny glue dot, which may not hold the part in place. However, you should be using two glue dots on each side of your 0402 component.
See under adherence force in paste a few days ago.
You should be able to hold the board sideways after placement and the components should stay in place, in particular if you are using a chip shooter for placement.
I sorta believe your Fuji is putting the parts on the spot. My hestitation goes back to a 0402 feeder cal thread that someone-er-other posted last week on SMTnet. Any relation?
Again, we�ve never seen this. Angles to consider are: 1 Placement machine induced torque: Is the P&P head applying twist to the component as either the component enters or during release of the component. The inertia of this torque may remain in the glue for sec and the dissipate by rotating. 2 What is the manufacturer�s intended end use of the glue you are using? => Is the glue intended for printed SMD attach? 3 Are you following all the manufacturer�s glue shelf life recommendations? 4 Are you observing all the manufacturer�s glue working life guidelines?
Finally, what level of skewing are we talking about? What portion of the component termination is off the pad?
Are you guys providing adequate board support during glue dispense and placement? I've had this same problem with 0603's that I was able to correct with adequate board support. Also, if you're using a Fuji glue machine, what are your temperature settings inside the GL? Make sure they're compatable with the glue manufacturers recommendations. Dispensing glue at too high a temp can effect the glue's green strength. I know a lot of companies that push the temp limit to increase the speed, but they give up placement accuracy and lose in the long run.