John: We have a similar product from MEI (Flip chip, C4, in a cavity mold BGA, die B/S exposed, running 8~9 watts). We put a heatsink/fan on this. Die area is about 400 mils on a side. We are using Loctitie 315. This is the same as L384, except the 315 has 5mil silica beads for self-leveling. Most of our problems came early on from our board assembly houses not following attachment instructions (this adhesive needs an activator). Might try this... > Bill Davis, Ph.D. > Diamond Multimedia Systems > Senior Scientist > Tel. 408.325.7868 > Cell. 408.888.5650 > e-mail: [log in to unmask] > > > > > -----Original Message----- > From: John Loveluck [SMTP:[log in to unmask]] > Sent: Thursday, November 19, 1998 2:26 AM > To: [log in to unmask] > Subject: Re: [TN] Attaching Al heatsink to Si die > > Hi Werner > > Thanks for replying. My question relates specifically to a heatsink > bonded > to the rear surface of the silicon die on top of a Motorola Power PC > (which > uses IBM C4 technology) on a ceramic BGA substrate. The silicon > surface > area available for heatsink attach is approximately 10mm square and > the > chip power dissipation is 7W. > > For previous generation (non BGA) products we used adhesive thermally > conductive tape bonded to the top of the ceramic pasckage, which > worked > fine as the surface area was about 30mm square. With the BGA package > structure the bondable area is down to 10mm square but the heatsink > has to > stay big (20mm square) to get the required heat dissipation. > > Motorola sort of recommend mechanically clipped heatsinks, but these > are > not practical in our application due to constraints of size and > availability, leaving us for at least the short term with the need to > find > an adhesive that can cope with the mismatch in CTE. Tape does not > give > enough bond strength. > > We are doing trials at present with Berqquist LA1000, a thermaly > conductive > low modulus adhesive, which gives good bond strength. The > manufacturer > offers versions with glass beads (4.9mil or 7mil) for control of bond > line > thickness, which may or may not be useful. > > We would like to know more about the long term reliability aspects of > this > adhesive. Does anyone have any data in similar applications? > > Regards > > John > > > At 18:30 17/11/98 EST, you wrote: > > > >Hi John, > >In a message dated 11/17/98 12:56:44, you wrote: > >>Does anyone have practical experience of the effects of thermal > expansion > >>mismatch on a thermally conductive glueline between a silicon die > (in our > >>case, Motorola MPC740 BGA Power PC processor) and an aluminium > heatsink? > >> > >>We have looked at several adhesives, some of which are much more > compliant > >>than others, and are looking for criteria on which to base the final > >decision. > > > >The answer to your question is: It depends (not meant to be funny). > >The higher the power dissipation, the more temp cycling (testing?), > the > larger > >the silicon die, the more compliant your die attach needs to be. > >What are you electrically connecting these die to? > > > >Werner Engelmaier > >Engelmaier Associates, L.C. > >Electronic Packaging, Interconnection and Reliability Consulting > >7 Jasmine Run > >Ormond Beach, FL 32174 USA > >Phone: 904-437-8747, Fax: 904-437-8737 > >E-mail: [log in to unmask] > > > > > > ################################################################ > TechNet E-Mail Forum provided as a free service by IPC using LISTSERV > 1.8c > ################################################################ > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in the body: > To subscribe: SUBSCRIBE TechNet <your full name> > To unsubscribe: SIGNOFF TechNet > ################################################################ > Please visit IPC's web site (http://www.ipc.org) "On-Line Services" > section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or > 847-509-9700 ext.312 > ################################################################ > ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################