Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Stencil Printing No lead

Views: 2758


Ev

#51488

Stencil Printing No lead | 21 August, 2007

Looking for pointers. We have a semi-automatic SMT Techniques stencil printer. We have had some problems with a recent job. Problems were in the areas of finer pitch ics (paste voids as well as paste shorts and some smearing) in certain locations on one side the pcb. The other side prints well larger footprints much fewer components. The pcb itself is about 5" in diameter it is a circular board in a 4 up panel configuration. It seems to get worse as the paste gets older. This is also the first job that is totally no lead. The question is: should we be looking at the operator? the paste? or the setup? in order to solve the quality of the print. Or are we missing something completely? Ev

reply »

#51490

Stencil Printing No lead | 21 August, 2007

Is it a clamshell type printer, opens on a hinge? If so you will never be able to reliably print with that type of printer. We had one of their printers and were never able to get it to print fine pitch reliably. It has nothing to do with the operator or setup.

James

reply »


Ev

#51491

Stencil Printing No lead | 21 August, 2007

Yes it is a clam shell type. What type of printer did you go to?

Ev

reply »

#51492

Stencil Printing No lead | 21 August, 2007

We went with a DEK ELA automated printer and have never been happier. We print down to 16mil (.4mm) with great results. I know this may be beyond your budget but just look for a printer that raises straight off the board with no hinge.

James

reply »

#51502

Stencil Printing No lead | 22 August, 2007

Have you tried the same setup with your leaded paste? Your lf paste might have different cold slump characteristics.

reply »

#51506

Stencil Printing No lead | 22 August, 2007

"The question is: should we be looking at the operator? the paste? or the setup?"

Yes. ;)

Those guys love to brag about their 4 corner height adjustment on those printers. The fact is it's a PITA and shouldn't be necessary in the first place. It's certainly not necessary on vertical lift machines.

It sounds like that could be a problem, in addition to the downside (is there an upside?) to it being a clamshell printer.

We have two of them and you can print down to 20 mils if you pay close attention to your setup (especially stencil and squeegee height and squeegee speed), align every board, and use fresh paste. It's never going to be fast, though.

reply »


Ev

#51510

Stencil Printing No lead | 22 August, 2007

Thanks for all responses really good feedback. I have placed a number of extra supports underneath each pcb in the panel and by checking each print diligently we seem to be able to keep running. Not feaseable at the moment to check out leaded paste on this assembly as suggested earlier. For the most part it seems that the smearing problem has gone. I do notice that one pcb is consistently good in the bottom left quandrant of the panel. Ev.

reply »

SMT in-printer dispensing

PCB Soldering Tools