Agree, if you talk GaAs, they are to be handled and attached and tested more careful than Si. We both hand- and autoplace them and have found that epoxying down them is not that easy, because even the machine's lowest force is too high: the epoxy is pressed aside and flows up the MMMIC side, something we don't like. If you mount MMICs with RF-power devices on (HEMT, PHEMT, HBT etc), they should be soldered and not epoxied. Ourselves, we do vacuum soldering to get voidfree joints. Until now (hopefully always)we have not had any defects registered from collet handling, nor from fine wire wedgebonding. There are many skilled users to speak with: CTS, NS in L.A., Northrop-Grumman, Raytheon, the US seems to have lots of companies busy with this stuff, and americans are normally very openminded and glad to tell how to make it. Best source should be your chip supplier.
Good Luck
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: Misner, Bruce [mailto:[log in to unmask]]
Sent: den 30 mars 2000 17:13
To: [log in to unmask]
Subject: Re: [TN] MMIC attach
James,
Most MMIC devices are low power enough to mount with Ag epoxy, however,
unlike bipolar or CMOS devices, they typically are made of very thin
(.004-.006) GaAs and contain air bridges. This means they are brittle and
you cannot contact the top side of the die. Hence die attach must be done
with tweezers for very low volume or a custom die collet for higher volumes.
Epoxy amount is critical to maintain a thin (.001), uniform interface
thickness for RF performance and prevent epoxy from coming over the top of
the die or contaminating the collet... typical epoxy fillets will not be
maintained.
Wire bonding is atypical as well. Ultrasonics tend to create microcracks or
worse and should be minimized. You can compensate for this through higher
substrate and/or bond tool temperatures.
Also be prepared for removing them from Gel Paks. You will probably need a
Gel Pak release station. Contact me off line if you need more help.
Best of Luck, they're a challenge,
Bruce Misner
> ----------
> From: Terveen, James @
> NARDAEAST[SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;Terveen, James @ NARDAEAST
> Sent: Thursday, March 30, 2000 9:27 AM
> To: [log in to unmask]
> Subject: [TN] MMIC attach
>
> I need a little help on a new design that Eng.in coming up with. They
> would like to take an Alumina substrate and attach a MMIC to it. The
> substrate is a MicroBGA. We have a clean room operation in our facility
> and do wire bonding but I do not have enough knowledge on how this would
> be done. Whether to solder it or use epoxy. and it either then what
> would the material be. So if anyone can help with how the mmic should
> be attached to the substrate or direct me to some good literature it
> would be greatly appreciated.
>
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