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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Problems with devices utilizing a

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Problems with devices utilizing a | 12 March, 2007

Our internal designers are employing SMT connectors that utilize a �PCB positioning boss� in conjunction with normal gull wing leads. The use of these devices is based on the advertised ability of the boss to prevent �mis-insertions� and assist in �connector retention�. Using the recommended hole diameters from the vendors has resulted in problems with some connectors �popping� off the substrate during reflow due to marginal PCB material/construction and the differences in the coefficient of expansion. We have also observed the inability to place the component at all due to a tolerance accumulation/mismatch between the part and substrate. By the time we capture all possible linear/hole diameter tolerance variations the hole in the substrate becomes too large to serve any purpose relating to the advertised advantages. Based on these observations we are trying to develop a case to forbid their use altogether and I am seeking additional input from other sources that process these devices to see if our experience is typical or abnormal. TIA

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Problems with devices utilizing a | 13 March, 2007

We have used thousands of them with no problems. They will not aid in "connector retention" unless you have a shear force at exactly the right angle. This is an advertising joke. They will help with alignment of the connector. Open your holes up so there is just enough play that the leads cant short to adjacent pads. You clearly are using too tight of a tolerance on your holes, regardless or the manufacturers reccomendations. In my personal opinion, unless you are placing them by hand, you dont need the pins. But, sometimes the lead times are so long on the version without pins you have no choice. It is also possible that you are buying crap connectors but I dont see how you could ever get the hole tolerance so tight that it adds mechanical strength to assembly and still be able to place it on a normal line, it would almost have to be a press fit.

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