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October 2008

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Subject:
From:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Joyce Koo <[log in to unmask]>
Date:
Fri, 10 Oct 2008 06:58:08 -0400
Content-Type:
text/plain
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text/plain (295 lines)
Have you try knife to kill the surface? Remove thin layer using flexible knife. Bond a smaller wire on site. Remove the wire using pull tester, rebond the same site using the large diameter wire.  Hopefully, it is small QTY part 

--------------------------
Sent using BlackBerry


----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Fri Oct 10 04:25:55 2008
Subject: Re: [TN] Need soldering advice ASAP!

The production manager is hunting me for a solution, quick one. He has proposed the operators to skip aluminium wire and parallel four 50 micron gold ball wires instead. I'm not happy with that either, because of the risk of gold/aluminum IMC (purple plague)with high currents and high temperature.  Furthermore, using four wires in parallel does not mean equality.  What do you think?

Inge



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Creswick, Steven
Sent: den 9 oktober 2008 21:33
To: [log in to unmask]
Subject: Re: [TN] Need soldering advice ASAP!

Inge,

Metal buildup in the bonding tool causing bond lifts??

I am of the same mindset as you and Wayne present.

Very confusing

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Thursday, October 09, 2008 3:26 PM
To: [log in to unmask]
Subject: Re: [TN] Need soldering advice ASAP!

I'm surprised. Heavy wire with Al use to be very uncritical. The high energy density  use to push aside all debris and if the metallisation isn't too

thin, a connection is easily created. And me too, also doubt  about voids.
We have already Xray'd and made bonding attempts on those with voids and

those with few or no  voids. Same result. If I speak nicely to Mr Murphy...
Inge


----- Original Message -----
From: "Thayer, Wayne" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, October 09, 2008 12:18 PM
Subject: Re: [TN] Need soldering advice ASAP!


I agree that some voids should not present a problem for the aluminum.
A test would be to look for voids on the Xray and then try bonding both on the void and off of it to see if there is some kind of "drum effect"
going on, but I doubt it.

Wayne

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Thursday, October 09, 2008 1:30 PM
To: [log in to unmask]
Subject: Re: [TN] Need soldering advice ASAP!

Already fixed, a glass of my home made wine is already standing on my desk!
Made on pumkins. English pumkins. American pumkins too bitter.

Bondlifting or do not stick.

No, dice or not jumping off..

Everything is checked: wire, wedge, parameters, clamps are new made, workholder polished to best planarity, preforms are controlled etc.  We get same bad result on the other heavy wire bonders.

Frit..oufff...no-no-no..mixed

Burnish good idea, will try that.

Our feeling is that it must be either the die surface or voids.

Inge



----- Original Message -----
From: "Creswick, Steven" <[log in to unmask]>
To: "TechNet E-Mail Forum" <[log in to unmask]>; "Inge"
<[log in to unmask]>
Sent: Thursday, October 09, 2008 10:09 AM
Subject: RE: [TN] Need soldering advice ASAP!


Inge,

Maybe you've had enough nuts and should switch to a liquid??



Bonds are just not sticking???

Understanding that voiding is not desired, but what leads you to believe that is the cause of the bonding problem?  Die coming up?

Are you absolutely sure nothing has changed in the clamping of substrate/package and that the bonding tool is firmly clamped in the transducer?

Cd is a new one to me too...

I've had some of our thick film golds outgas substantially, although the vacuum reflow helped a great deal.

If it is a mixed bonded gold, it is possible that you have a slightly glass-rich surface.  Some are more sensitive to furnace atmosphere contaminates as well.

Doubt you are using a fritted gold.

Burnish before reflow if a de-wetting issue?


Steve





-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Thursday, October 09, 2008 12:53 PM
To: [log in to unmask]
Subject: Re: [TN] Need soldering advice ASAP!

50%

Inge

I have to get an advice soon, because I have consumed a 250 gram box of cashew nuts while searching for tips , and reach for another one...burp..


----- Original Message -----
From: "Creswick, Steven" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, October 09, 2008 9:41 AM
Subject: Re: [TN] Need soldering advice ASAP!


Are the voids so huge as to PREVENT good mechanical clamping of the die for bonding?  - sorry

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Creswick, Steven
Sent: Thursday, October 09, 2008 12:37 PM
To: [log in to unmask]
Subject: Re: [TN] Need soldering advice ASAP!

Ingemar,

Ours used to be CrNiAg backside metallization.

My experience with the resultant AuSnAg alloy that forms is that once it has reflowed, it virtually is impossible to rework [if you ever wanted to].

Outgassing of the substrate metallization?  Thin film or thick?
Obviously, thick film worse.

Are the voids so huge as to provide good mechanical clamping of the die for bonding?  It would seem to have to be absolutely terrible voiding to cause that.  Is there something else going on, like a flux, or change in clamping, etc.

Seems like I have bonded some really badly voided parts with out issue

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Thursday, October 09, 2008 12:00 PM
To: [log in to unmask]
Subject: [TN] Need soldering advice ASAP!

Hi all, especially the Indi-man,
We have soldered IRC's power MOSFET (100-250  W) dice for a decade without problems. They use to be vacuum soldered to a solderable gold thickfilm
Al2O3 substrate with AuSn 50 micrometer preforms. Now there is a production stop because of Al heavy wire wedge bonding problems. My analysis of this case points at the presence of large voids in the solder joints  or maybe partly dewetting (FineFocus is good but the resolution is not sufficient to make me sure), something the US mechanical waves don't like. The die backside is plated with something that I don't recognize: Cadmium over Silver over Nickel. What the heck is that? Anyone who can figure out if AuSn is the best preforms for that plating?
Thanks
/Inge

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