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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


pallet design for thin pcb's

g cronin

#9421

pallet design for thin pcb's | 22 September, 1999

i'm sure everyone has run into this at one point or another. I have a thin pcb .025 that is single up that has to be built on a pallet. does anyone have any tricks to the pallet design that will help to hold these boards down during the screen/assembly process. remember nothing can go above the height of the pcb because of the screening. and no we cannot have these come in pallets from the board house, there is a very thin area of the pcb that the customer has found breaks if they are taken out of pallets.

any thoughs?

thanks

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#9422

Re: pallet design for thin pcb's | 22 September, 1999

| | i'm sure everyone has run into this at one point or another. I have a thin pcb .025 that is single up that has to be built on a pallet. does anyone have any tricks to the pallet design that will help to hold these boards down during the screen/assembly process. remember nothing can go above the height of the pcb because of the screening. and no we cannot have these come in pallets from the board house, there is a very thin area of the pcb that the customer has found breaks if they are taken out of pallets. | | any thoughs? | | thanks | | You should use pallets that stand the reflow as well so that no separation will take place before it is really safe. They should be build for tight fit out of the same material the PCB consists to prevent thermal mismatch with some openings for easy removal. Or you have a loose fit design with metalpins attached matching PCB-drillholes (I think 2 diagonal will do) with a tight fit of drillhole and pin. The pins do have a hight after mounting that does not exceed PCB thickness. Another more expensive possibility is to have a loose fit and some kind of clamping mechanism, excentric mounted round shapes that can be adjusted with a srewdriver towards the PCB to hold it tight and where the mechanism does not exceed PCB-hight, that might be nessary if tolerances of PCBs are to be expected.

I had the thing with those pins.

Keep things simple Wolfgang

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Boca

#9423

Re: pallet design for thin pcb's | 22 September, 1999

| | | | i'm sure everyone has run into this at one point or another. I have a thin pcb .025 that is single up that has to be built on a pallet. does anyone have any tricks to the pallet design that will help to hold these boards down during the screen/assembly process. remember nothing can go above the height of the pcb because of the screening. and no we cannot have these come in pallets from the board house, there is a very thin area of the pcb that the customer has found breaks if they are taken out of pallets. | | | | any thoughs? | | | | thanks | | | | | You should use pallets that stand the reflow as well so that no separation will take place before it is really safe. | They should be build for tight fit out of the same material the PCB consists to prevent thermal mismatch with some openings for easy removal. | Or you have a loose fit design with metalpins attached matching PCB-drillholes (I think 2 diagonal will do) with a tight fit of drillhole and pin. The pins do have a hight after mounting that does not exceed PCB thickness. | Another more expensive possibility is to have a loose fit and some kind of clamping mechanism, excentric mounted round shapes that can be adjusted with a srewdriver towards the PCB to hold it tight and where the mechanism does not exceed PCB-hight, that might be nessary if tolerances of PCBs are to be expected. | | I had the thing with those pins. | | Keep things simple | Wolfgang | I have used pallets with a custom hold down scheme, I think they call it a 'forcer'. The 'forcer' is mounted to the pallet, grabs the fab by the tooling holes (diagonal is ideal like Wolfgang mentioned), is spring loaded, and does not extend up beyond the top edge of the fab. And ya know what? They WORK! It's ideal for this kind of application. The only place I know of which does these is Summit Precsion in Phoenix AZ, (602) 268-3550. Contact name is Dennis Miller. They are great people to work with too.

Boca

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DaveH

#9424

Re: pallet design for thin pcb's | 23 September, 1999

For another excellent vendor try EMC GlobalTechnologies in Pennsylvania (215)340-0650. Contact Marty Wetzel. | | | | | | any thoughs? | | | | | | thanks | | | | | | | | You should use pallets that stand the reflow as well so that no separation will take place before it is really safe. | | They should be build for tight fit out of the same material the PCB consists to prevent thermal mismatch with some openings for easy removal. | | Or you have a loose fit design with metalpins attached matching PCB-drillholes (I think 2 diagonal will do) with a tight fit of drillhole and pin. The pins do have a hight after mounting that does not exceed PCB thickness. | | Another more expensive possibility is to have a loose fit and some kind of clamping mechanism, excentric mounted round shapes that can be adjusted with a srewdriver towards the PCB to hold it tight and where the mechanism does not exceed PCB-hight, that might be nessary if tolerances of PCBs are to be expected. | | | | I had the thing with those pins. | | | | Keep things simple | | Wolfgang | | | I have used pallets with a custom hold down scheme, I think they call it a 'forcer'. The 'forcer' is mounted to the pallet, grabs the fab by the tooling holes (diagonal is ideal like Wolfgang mentioned), is spring loaded, and does not extend up beyond the top edge of the fab. And ya know what? They WORK! It's ideal for this kind of application. The only place I know of which does these is Summit Precsion in Phoenix AZ, (602) 268-3550. Contact name is Dennis Miller. They are great people to work with too. | | Boca |

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#9425

Re: pallet design for thin pcb's | 23 September, 1999

| | i'm sure everyone has run into this at one point or another. I have a thin pcb .025 that is single up that has to be built on a pallet. does anyone have any tricks to the pallet design that will help to hold these boards down during the screen/assembly process. remember nothing can go above the height of the pcb because of the screening. and no we cannot have these come in pallets from the board house, there is a very thin area of the pcb that the customer has found breaks if they are taken out of pallets. | | any thoughs? | | thanks | | g: Get a piece of FR4 (maybe unclad if you plan to slot paste all over it) from your fab house. Cut it to a convient size for your conveyors. Drill holes in the FR4 to correspond with the tooling holes on the board you're assembling. Add some press-fit tooling pins at the correct height. Go.

We've talked about sourcing tooling pins on SMTnet before. Check the archives. If that doesn't work, I have other sources.

Ta

Dave F

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