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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Gold Finger Wear



Gold Finger Wear | 20 December, 2000

Question: How many insertion/removal cycles can be expected of gold finger contacts?

Problem: We manufacture a class 2 PCBA with gold finger contacts whose application will require repeated insertion and removal into card edge connectors (mother board/daughter board relationship). To confound matters, we have no control over which edge connector the board might meet.

I've contacted several connector vendors but no luck (i.e. estimate based upon plating thickness). I've been unable to locate any sort of reference. Perhaps one of you has converted a production board into test equipment and has some sort of idea or has done some sort of study. Any help would be appreciated. Thanks.

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Travis Slaughter


Re: Gold Finger Wear | 20 December, 2000

I don�t have the answer for you but it would not be difficult to make a fixture to find out. Combine a counter, pneumatic cylinder, and a solenoid in such a way to do the job for you. Cylinder pushes the card into the connector, when contact is made pulls the card out, count 1, contact lost, push back in�. Using the contact of the card and the connector to drive the solenoid the first time contact is not made it all stops with the final tally on your counter. Leave the thing running all day, week, month or however long it takes to fail. Used a similar setup to test those mini-stereo headphone connectors, wow can they take a beating.

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Re: Gold Finger Wear | 20 December, 2000

Talk about glam jobs � About once a month, we�d go over to the slaughter yard to get cows� teeth for Dr. Mueller. Then we�d fixture them on their side and run them in a machine that scrubbed them with a brush for weeks. The cool thing about cows teeth is they are comprised of roughly concentric hard and soft cylinders of dental running from top to bottom. � For cows, it made a sharp cutting surface for chomping grass off at the stem. � For us, we could count the number of layers to evaluate the wear characteristics of different tooth pastes.

Beavers� teeth have hard front dental and the back is soft, so they�re no good for wear experiments, beyond the issue of the difficulty of getting beaver teeth. Not coincidentally, the venerable P-38 US GI can opener was designed on the same principle to be self sharpening.

OK, enough teeth stores. Years ago, Norm Einarson ran an experiment to determine insertions from a gold plated board into a connector. Boards were all the same thickness (0.062") and had 100 uinches base nickel. Results were: � 100 uinches gold = 500 insertions � 50 uinches gold = 300 insertions � 30 uinches gold 50 to 75 insertions � 20 uinches gold 10 insertions.

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