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Nickel/Hard Gold thickness

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#65917

Nickel/Hard Gold thickness | 24 February, 2012

I need to be sure of the Nickel/Hard Gold thickness to be specified on our drawing. We use hard gold on a slip ring pcb that has brushes riding over the conductive surface, so soldering is not the issue. I read through the hard gold vs immersion gold thread. Is 150 microinches of Nickel and 5 microinches of Gold sufficient?

Thanks,

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#65920

Nickel/Hard Gold thickness | 25 February, 2012

I'm more familiar with wear surfaces on the edge of boards that are inserted into a card rack. So, I'm not sure how to relate to your "hard gold on a slip ring pcb that has brushes riding over the conductive surface." Is your application a board that makes contact to a connector arm as it rotates? [Would you post a picture?]

Number of insertions is affected by the contact normal force that varies significantly between suppliers and designs. Other factors that also affect insertions are plating porosity, plating adhesion, particulate contamination, and contact geometry.

IPC-2221 says something like ... For edge connectors and areas not to be soldered:
* Nickel - 2.5um [~100uin] min [Class 2 & 3].
* Gold - 0.8um [~30uin] min [Class 2], 1.3um [~50uin] min [Class 3].

In this, I'd guess:
* 30 uin gold => 50 to 75 insertions
* 50 uin gold => 300 insertions

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#65925

Nickel/Hard Gold thickness | 27 February, 2012

Hi Dave,
Picture a camera mounted on top of a fixed base that pans 360 deg. back and forth. The motor connects through a circular slip ring board with brush connection. The rings are hard gold and the typical brush material is soft. Unlike the armature in a motor that runs continuously at high rpm, this application does a slow pan when in use.
We are calculating the total expected hours of use and want to be sure we have adequate hard gold plating to provide a reliable connection over the life of the product.

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