Copper Contact to Gold Surface Design Question
04-18-2008, 05:40 PM, (This post was last modified: 04-18-2008, 05:43 PM by gpalermo.)
Copper Contact to Gold Surface Design Question

I'm designing a "burn-in" station for a unique laser diode chip-on-carrier utilizing a 59 gold,99.99% electrical-grade), platinum, and tungsten contact pad for electrical conduction. The system is going to utilize soft, beryllium-copper 97.9% Cu - 2.1% Be leaf spring contacts to transmit the power upon contact.

This is the full setup of one rack with several carriers:

(link dead)

The full view is not really detailed enough, so here is a zoomed view showing the actual contact pads and spring on in place:

(link dead)

And just to get real detailed, I made a profile sketch showing the leaf spring contact unstressed in a bounding box. Please disregard the corner of the blade that is intersecting at the bottom right as that is being issued:

(link dead)


From this small background (which I hope is sufficient), I just wanted to know the following:

1) Is there a threshold force I can design the spring to exert upon the surface of the metalized contact pads to minimize, and if possible, eliminate surface defects?

2) Is there a way I can design the spring to fold easier upon the surface?

3) Are there any coatings or platings I can apply to the contact surfaces of the leaf spring that will allow an equally capable electrical power transmission between the two or give a surface finish that will eliminate scratching?

I'm under the impression that the Rockwell B Hardness of the CuBe leaf spring is 45-78 while the gold is so soft it can't be measured on the same scale. The only data I can find on the 59 gold is that it has a Vicker's hardness of 25-170, which is a huge range.... I do believe a Vicker's hardness of 150+ from the conversion chart I found here shows that the gold will be about as hard or harder than the copper-beryllium, which eliminates the worry altogether since a "harder" material cannot be scratched by the lesser one. Then again, that's just my knowledge from undergraduate materials classes so that could be a wrong assumption.

Oh, and nice forum!

My name is Graham and I work for a company called SemiNex which designs and manufactures high-power 1450 nm laser diodes.
04-21-2008, 03:03 PM,
RE: Copper Contact to Gold Surface Design Question
Hi Graham

Sign0016 to the Surface Engineering Forum.

Not sure what "59 gold" is but if it is relatively pure gold, then the hardness (~30 HV) will probably be much lower than the beryllium copper alloy. I would consider gold plating for the leaf springs primarily for good electrical contact and similar hardness. The leaf spring design I think should be optimised to give contact with minimum sliding motion between contact faces with the minimum force required to give the required electrical contact.

Hope that helps.
04-21-2008, 03:28 PM,
RE: Copper Contact to Gold Surface Design Question
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