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Wirebond issues near SM

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CB

#60070

Wirebond issues near SM | 8 October, 2009

We are currently wirebonding MCMs with surface components located in very close proximity to wirebond pads, which are gold plated. We are ball bonding with 99.99% Au wire. Normally we do not have problems, however if product has been reflowed several times, and with no visible contamination on pads, wirebond adhesion is greatly reduced . Pull strength normally 7-9 gms is now less than 2.0gms . I plan to have surface analyzed. Solder is pb free. Years ago, I remember reading about something called "Sn migration" , where Sn was found to "migrate" during reflow and deposit on nearby bond pads. Has anyone experienced this problem? -CAB

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#60182

Wirebond issues near SM | 26 October, 2009

Hi,

Is your problem solved? If yes then how? Have you tried Plazma cleaning before wire bonding?

BR

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#60227

Wirebond issues near SM | 29 October, 2009

Hi. We are doing Au bonding on Al bond pad not Au plated. If pull strength is less than 2.0g, i think that the ball or stich may be lifted from bond pad. And the value become lower after several reflow. I expect that the surface of bond pad may be contaminated or oxidized during reflow. To solve this problem, try to bond after you cleaned the bond pad with eraser or other cleaning method.

And, when plating Au, Ni is plated first to prevnet the Sn migration from condutor line ( I think). So you need to check the plating thicnkness of Ni and Au.

Thanks.

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CB

#60234

Wirebond issues near SM | 30 October, 2009

We have performed some EDS analysis and found high percent (approx 18% ) of Ni on surface of gold pad. Found Tungsten as well. This is an HTCC alumina package. Thickness of gold was confirmed and found to be in spec. We believe we are dealing with a surface which is porus after high temp firing, then Ni & W "migrating" to surface during our lead-free reflow.

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#60243

Wirebond issues near SM | 31 October, 2009

> We have performed some EDS analysis and found > high percent (approx 18% ) of Ni on surface of > gold pad. Found Tungsten as well. This is an > HTCC alumina package. Thickness of gold was > confirmed and found to be in spec. We believe > we are dealing with a surface which is porus > after high temp firing, then Ni & W "migrating" > to surface during our lead-free reflow.

Hi

What is thicknes of fired Au conductor ? faced similar bonding problem when thickness achieved was below 5-6 microns after HT firing. Plazma cleaning of PFT is also helping clening Au surface contamination

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CB

#60269

Wirebond issues near SM | 2 November, 2009

Au measured out( using XRF)at 55-75micro-inches. Within spec, per out QA dept.

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#60575

Wirebond issues near SM | 30 November, 2009

Ni is coming up through soft Au.

Sam forman

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