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SMT assembly on Punch/return boards

Hella Electronics Corporation

#4060

SMT assembly on Punch/return boards | 18 May, 2000

Is it possible to print, place and reflow punch and return style boards in a high production environment

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#4061

Re: SMT assembly on Punch/return boards | 18 May, 2000

Ed: It might be possible, never tried tho, but if an engineer wandered in, talking about it ...

Printing: Makes me pretty nervous, because punched boards are not planar, don�t stay planar, and are inconsistently not planar. If I could work-out the other issues, I�d want to dispense this type of board. Yano, if it could support down stream processes and all that ... Registration could be an issue for both printing and dispensing, but not on the scale of planarity. Placement: Makes me a little nervous, because placement force could pop boards from the web, but I�d guess that this could be controlled with proper support and programming. Again, registration could be an issue, but less concerning. Reflow: Makes me more than a little nervous, considering the unbalanced construction and native board bow, but that would be a function of ramp rates and what not. It would be wild if the bow during reflow popped boards from the web.

My2� Dave F

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Dean

#4062

Re: SMT assembly on Punch/return boards | 18 May, 2000

...ahh....memory lane.

10 years ago I worked on a project for a customer who needed a low cost, high volume board for RFID tags for cows (yes, moo). These boards were 0.50 inch in diameter, 50 per panel, double sided SMT punch style fabs. 300,000 boards later, I feel qualified to answer your question.

1. Delicate handling procedures required. Punchouts will fall out at all stages of your process (stock room to shipping) 2. Printing is difficult as punchouts tend to rotate in the web randomly and must be "pre-alligned" prior to print and P&P. Huge handling overhead! 3. Random punchouts may stay stuck to stencil. Vacuum hold down required. 4. Fixturing required for P&P process. 5. Fixturing required for reflow process. 6. Hope you can use no-clean otherwise your gonna loose 'em in the wash process.

I would seriously evaluate the handling overhead and required fixturing vs. break-outs or V-scoreing (if square). In retrospect it was a major headache where no gains were achieved using die punch.

Hope this helps.

Dean

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Boca

#4063

Re: SMT assembly on Punch/return boards | 19 May, 2000

Ed, I workded with punch and replace fabs yeeeeears ago, major pain! Dave's right, planarity is the biggest problem, then inconsistent retention in the panel, then ANY retention in the panel. If you can get paste on them, you may be able to place them, and they may behave thru reflow. A lot of 'ifs' and 'mays' to get past for anything resembling a reliable process. Oh, has anyone mentioned to you that the panel bows, and of course the amount of panel bow varies from panel to panel, and lot to lot. We were an OEM and could afford to tool for punch and replace on the production floor, we still got rid of them because of the grief they caused, just in thru hole assembly.

Boca

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Travis Slaughter

#4064

Re: SMT assembly on Punch/return boards | 19 May, 2000

Did the cow tag thing too hu? � inch yea, 50 in a panel sounds right did the rows happen to be offset (looking a little like a honeycomb)? We didn�t have a great deal of trouble with the boards falling out at most it was a minor inconvenience. Perhaps yours where 31 mil boards 62 mil would hold better for obvious reasons. Fixturing is defiantly a concern especially if it�s going to be a low volume runner.

PS. Dave my tags where about 5 years ago and maybe 100,000 total.

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Travis Slaughter

#4065

Re: SMT assembly on Punch/return boards | 19 May, 2000

Did the cow tag thing too hu? � inch yea, 50 in a panel sounds right did the rows happen to be offset (looking a little like a honeycomb)? We didn�t have a great deal of trouble with the boards falling out at most it was a minor inconvenience. Perhaps yours where 31 mil boards 62 mil would hold better for obvious reasons. Fixturing is defiantly a concern especially if it�s going to be a low volume runner.

PS. Dave my tags where about 5 years ago and maybe 100,000 total.

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Travis Slaughter

#4066

Re: SMT assembly on Punch/return boards | 19 May, 2000

Did the cow tag thing too hu? � inch yea, 50 in a panel sounds right did the rows happen to be offset (looking a little like a honeycomb)? We didn�t have a great deal of trouble with the boards falling out at most it was a minor inconvenience. Perhaps yours where 31 mil boards 62 mil would hold better for obvious reasons. Fixturing is defiantly a concern especially if it�s going to be a low volume runner.

PS. Dave my tags where about 5 years ago and maybe 100,000 total.

reply »

Boca

#4067

Re: SMT assembly on Punch/return boards | 19 May, 2000

Ed, I workded with punch and replace fabs yeeeeears ago, major pain! Dave's right, planarity is the biggest problem, then inconsistent retention in the panel, then ANY retention in the panel. If you can get paste on them, you may be able to place them, and they may behave thru reflow. A lot of 'ifs' and 'mays' to get past for anything resembling a reliable process. Oh, has anyone mentioned to you that the panel bows, and of course the amount of panel bow varies from panel to panel, and lot to lot. We were an OEM and could afford to tool for punch and replace on the production floor, we still got rid of them because of the grief they caused, just in thru hole assembly.

Boca

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Travis Slaughter

#4068

Re: SMT assembly on Punch/return boards | 19 May, 2000

Did the cow tag thing too hu? � inch yea, 50 in a panel sounds right did the rows happen to be offset (looking a little like a honeycomb)? We didn�t have a great deal of trouble with the boards falling out at most it was a minor inconvenience. Perhaps yours where 31 mil boards 62 mil would hold better for obvious reasons. Fixturing is defiantly a concern especially if it�s going to be a low volume runner.

PS. Dave my tags where about 5 years ago and maybe 100,000 total.

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Travis Slaughter

#4069

Re: SMT assembly on Punch/return boards | 19 May, 2000

Did the cow tag thing too hu? � inch yea, 50 in a panel sounds right did the rows happen to be offset (looking a little like a honeycomb)? We didn�t have a great deal of trouble with the boards falling out at most it was a minor inconvenience. Perhaps yours where 31 mil boards 62 mil would hold better for obvious reasons. Fixturing is defiantly a concern especially if it�s going to be a low volume runner.

PS. Dave my tags where about 5 years ago and maybe 100,000 total.

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Travis Slaughter

#4070

Re: SMT assembly on Punch/return boards | 19 May, 2000

Did the cow tag thing too hu? � inch yea, 50 in a panel sounds right did the rows happen to be offset (looking a little like a honeycomb)? We didn�t have a great deal of trouble with the boards falling out at most it was a minor inconvenience. Perhaps yours where 31 mil boards 62 mil would hold better for obvious reasons. Fixturing is defiantly a concern especially if it�s going to be a low volume runner.

PS. Dave my tags where about 5 years ago and maybe 100,000 total.

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Travis Slaughter

#4071

Re: SMT assembly on Punch/return boards | 19 May, 2000

Oops looks like all those browser failures sent it through just didn�t let me know sorry everyone.

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