At what point does PCB hole interference become a real problem? .005"? .001"?
At what point does PCB hole interference become a real problem? .005"? .001"?
(OP)
I'm the sole mechanical engineer on an electronic package wherein a small polyimide PCB will be mounting to an aluminum 6061 housing via #4-40 screws. Due to my lack of experience, I'm not sure how much concern to place on a worst-case .0015" interference due to the tolerance stack of the holes - the housings have been made and the PCB drawing is headed to our vendor shortly, so making changes to controlled drawings at this point is to be avoided unless really necessary (I didn't make these drawings, just began work here). .0015" is small enough that it seems to me it wouldn't be a problem in the rare chance it did occur - you wouldn't even need a drill to open up the hole, just some caution to avoid cross threading, and the screw will deform the board that .0015".
Anyone who's had experience with misaligned PCB / housing holes - is .0015" that big of a deal?
Anyone who's had experience with misaligned PCB / housing holes - is .0015" that big of a deal?






RE: At what point does PCB hole interference become a real problem? .005"? .001"?
Tunalover
RE: At what point does PCB hole interference become a real problem? .005"? .001"?
Tiny metal shavings have been known to cause trouble in electronics.
Mike Halloran
Pembroke Pines, FL, USA
RE: At what point does PCB hole interference become a real problem? .005"? .001"?
Quite true if the holes are plated. We don't know if they are.
Tunalover
RE: At what point does PCB hole interference become a real problem? .005"? .001"?
Thanks for your help = definitely has tipped the scales in my mind. I will bring this to the attention of my managers on Monday.
RE: At what point does PCB hole interference become a real problem? .005"? .001"?
Also for a #4-40 screw I'd use a .125-.128" diameter hole.. or .116" dia if a "close fit" is required.
And make sure you leave plenty of clearance for the head of the screw so you don't have to use insulating washers.. I hate it when "designers" put traces so close to mounting holes. Solder mask should NEVER be relied upon for insulation.