Ultrasonic (typ Al wire) wedge bonding can be successfully performed on an immersion gold
finish. The thicker gold, minimum 20 microinches of "true electroless", is normally used for
gold thermosonic/thermocompression ball bonding.
Note: I've heard reports (unsubstantiated) that some Japanese companies are having "good"
success with thermosonic ball bonding on immersion gold. Just thought I'd throw
that in.
Tracy Tennant
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De: Coderre - JCCODERR BRMVM1
***************************************************************
CLASSIFICATION NON-CLASSIFIE ( ) CONFIDENTIEL ( )
Objet: BGA finish
Typically we talk of 5-10 microinches of gold. This is a self-limiting
process with the upper limit being in this range. The 3-5 is indeed
too tight and may represent a given immersion gold process. As for
wire bonding, the boards would typically go through an additionnal
"true electroless" gold process, depositing a minimum of 20 microinches.
Two different gold thicknesses means one needs a compatible masking
process which we are presently introducing for some of our customers.
Merci/Regards
Directeur Ingenierie MLC / MLC ENG. MGR
Dept 881/23 BRMT (tel. 514-534-6591, US tieline 552)
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