Apparently, the Obama fever has not stopped TN conversation. Too many old foxes, do not bother I guess.
As to the topic, not our experience. We ran aging tests in elevated temperature on some packages, no bias, and nothing happened. Then we did same with very high current through the bond wires, and got horrible growths of Au/Al IMC products around the bond site. Finally, the bond wires lifted. We draw the conclusion, that the high current caused a temperature rise in the bondwire itself, thus adding some thermodynamic activity.
/Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Woolley, Mark D. (Mark)
Sent: den 6 november 2008 00:09
To: [log in to unmask]
Subject: Re: [TN] AL CU DENDRTIES INSIDE PLASTIC IC
Purple plague is an intermetallic alloy that is formed at the junction of the Aluminum pad where the Gold bondwire is bonded. But this is not a dendrite. It is a multi-crystalline growth that appears as a dark or purple ring around the ball of the gold bondwire. Typically dendrites, which will grow within a contaminated plastic IC, do not contain gold.
All it takes is the aluminum, moisture, and an electric field.
In the past purple plague has been generally caused by high temperature whether or not the IC is powered. It usually causes an open circuit
(eventually) due to Kirkendahl voiding at the interface. With today's very closely pitched bonding pads the purple plague growth may be able to bridge between two adjacent bonding pads.
But again, this is not a dendrite. Dendrites need an electric field to induce growth, purple plague occurs in the absence of an electric field.
It occurs at some rate continuously, but at normal operating temperatures grows so slowly that it is not considered a primary factor in calculating the lifetime of an IC.
mark
Mark Woolley
PTRL Laboratory
Avaya, 1300 West 120th Ave, Area 33, Westminster, CO, 80234
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roberts, Jon
Sent: Tuesday, November 04, 2008 3:39 PM
To: [log in to unmask]
Subject: [TN] AL CU DENDRTIES INSIDE PLASTIC IC
Has anyone have knowledge or experience with AL Cu Dendrites growth in plastic IC components? Reports or other information is appreciated, Thanks, Jon
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