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Date:
October 08, 2009 11:33 AM
Author:
CB
Subject: Wirebond issues near SM
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
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60070)
Date:
October 26, 2009 07:37 AM
Author:
Mysmt
Subject: Wirebond issues near SM
Hi,
Is your problem solved? If yes then how?
Have you tried Plazma cleaning before wire bonding?
BR
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60182)
Date:
October 29, 2009 08:19 PM
Author:
Jeong Ju-young
Subject: Wirebond issues near SM
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.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60227)
Date:
October 30, 2009 09:19 AM
Author:
CB
Subject: Wirebond issues near SM
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.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60234)
Date:
October 31, 2009 01:22 AM
Author:
Mysmt
Subject: Wirebond issues near SM
> 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
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60243)
Date:
November 02, 2009 04:24 PM
Author:
CB
Subject: Wirebond issues near SM
Au measured out( using XRF)at 55-75micro-inches. Within spec, per out QA dept.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60269)
Date:
November 30, 2009 11:41 AM
Author:
sforman1
Subject: Wirebond issues near SM
Ni is coming up through soft Au.
Sam forman
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60575)
