Bill, Yeh! Isn't it nice they can't kill us - no matter how hard they try! Roger! that die planarity comment! I never thought that I would long for the day when the die were as large as your fingernail and had a couple hundred wires each. Those were the easy days - just didn't realize it then!! Too soon old, and too late smart. Steve -----Original Message----- From: Bill Christoffel [mailto:[log in to unmask]] Sent: Wednesday, August 28, 2002 3:09 PM To: TechNet E-Mail Forum.; Creswick, Steven Subject: RE: [TN] Die attach/bonding material Steve, (Nice to talk with another Chip & Wire guy) One final addition to your comments, not only is "theta" placement critical but keeping the device planar with respect to the substrate (PCB/Alumina/etc.) becomes extremely important when dealing with PR systems on subsequent wire bonding processes. Surface reflection (especially on LED die) dramatically changes the PR image. We have found that as little as .1 mil variation in die bonded flatness with cause a PR failure, and when your bonding 800+ LED die on a single board this can become a huge issue. Bill -----Original Message----- From: Creswick, Steven [mailto:[log in to unmask]] Sent: Wednesday, August 28, 2002 11:48 AM To: [log in to unmask] Subject: Re: [TN] Die attach/bonding material Victor, I ditto the comments made by Bill (below). With respect to polymeric attachments - the cured bondline thickness (adhesive thickness beneath the device) is somewhat determined by device size, equipment set-up, and material requirements. With most 'normal' die attach adhesives, you will get something like 0.5-1.5 mils (0.0005-0.0015") of bondline thickness for die in the size range of 8-50 mils per side. Larger die usually result in greater bondline thicknesses - partially by design (to better absorb stresses). For a device 0.250" square, I would expect a bondline thickness of around 2-2.5 mils (unless, by design, or material requirement, I was seeking something different). Some low-stress die attach materials actually seek bond lines in excess of 3 mils. Check with your polymer supplier for their specific process recommendations Your placement equipment has a role in the process too. If you go and try to place a 10 mil square device with a whopping 300-400 grams of placement force, you can count on your bondline thickness being on the low side (and or a crushed device or pick up tool). Now then, if you were to place it with a more reasonable 15-30 grams, you may find my numbers to be more realistic. Everthing is relative to your set-up and materials choices - no one can second guess from a distance. With respect to fillets - If you want to maximize heat transfer out of the chip, keep your fillets up. How high?? Personnally, if you are 50% up the side of the chip you are high enough! Why risk buggering up the wire bonding process with adhesive resins which may wick up the side and over the top of the chip. If you do not have the realestate to create larger fillets - your design is your limiting factor. Generally, fillets improve die shear strength (by effectively increasing the contact area). If you have a 'normal' 18-20 mil thick device, and you have fillets 5-8 mils up the sides - that should look nice! IF you had a 4 mil thick LED and you have fillets that tall, you just rendered the chip non-usable!! THere goes "its all relative" thing again. With respect to skew - How much skew can your wire bonder accept before the pattern recognition systems fails to capture the image? 5°? 10°? If you have wires crossing where they should not be - you have too much skew, otherwise "too much" is somewhat established by your design. Hope this helps a little bit (more/too) Steve Creswick - Gentex Corporation -----Original Message----- From: Bill Christoffel [mailto:[log in to unmask]] Sent: Wednesday, August 28, 2002 8:34 AM To: [log in to unmask] Subject: Re: [TN] Die attach/bonding material IMHO, some of the best information regarding die attach (alloy or polymeric) can be found in good old MIL-STD 883 (Method 2017 section 3.1.2, Element Attach) Note: a lot depends on the specific type of component due to defining active circuit area. If you have specifics feel free, this has been my area for over 20 years. Bill C. Advanced Manufacturing Engineer NorLux Corp. -----Original Message----- From: Victor Hernandez [mailto:[log in to unmask]] Sent: Tuesday, August 27, 2002 1:22 PM To: [log in to unmask] Subject: Re: [TN] Die attach/bonding material Importance: High Mr. MoonMan & Fellow TechNetters Can you please direct me to some literature/Requirement for die attach/bonding material thickness. Min and Max thickness. How far up the thickness of the die can the bonding material cover. Along that same line what is the skew aloud. victor, ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------