Rick, Could you provide a little more info, such as how large is device and the bump dia & pitch? Number I/O's? Is the flip chip bump composed of Sn63, or a IBM C4 structure? How large are the corresponding solderable pads on the PWB? How close are the nearest adjacent components? How many do you have to put together? Are you planning to co-reflow the FC with SMD's, or secondary reflow? What dispensing equipment do you have available to use? How do you plan to align and place the flip chips? Indium (and others) make no clean flip chip fluxes. One can either dip the solder bumps approx 1/3 to 1/2 way of their height into a paste-like flux, or jet or dispense a wee bit of the same flux in a very low viscosity version. I believe that Indium's part number designation is FC-NC-LT-A, B, C, D (where FC means Flip Chip, NC = no clean, LT=low temp (Sn63 like) and A thru D denote viscosity (A=like alcohol, D= like a paste flux). Big, oversize (or otherwise 'fat') fillets are visually unappealing, and (in my testing) less reliable than small, but uniform fillets. Most underfills that are applied after FC attachment will require the component to be heated to 70-90°C to enhance the capillary flow of the material. Post-dispense cures range from 125°C to 150°C, depending on supplier, etc. etc. Times range from minutes to about an hour. Rework after underfill cure is a pain, so essentially be assured that all is well before sealing it up tight with underfill. Scads of people to supply underfills - Dexter Hysol (now part of Loctite), Ablestik Labs, Kester, Alpha, Emerson & Cuming (Ablestik), Loctite, ..... Placing the chip by hand may not be the smartest thing to do, but with a reasonable setup, and small die (say less than 0.100" square) you should be able to dispense by hand with something similar to an EFD dispenser. Underfill from two adjacent sides only - let the capillary flow bring it under the chip and to the other sides. For larger chips, one might be better to use a dispenser that you can program a path. Whatever you do, do not allow the underfill wavefront to deplete the available reservior (excess material not under the chip). If the reservior is depleted, you can pull air under the chip - oops! Do you plan to check for underfill voids? X-ray generally will NOT work! Got an acoustic microscope?? What environmental requirements do you have to meet? Parting shots - If is a low rel, cheap & dirty PWB, you may get away with it. If it is a higher quality project, where the customer can come back and bite you - tread carefully. It may appear easier than it actually is Have fun! Steven Creswick CTS RF Integrated Modules At 10:57 AM 2/15/01 -0800, you wrote: >We've been asked to do a small proto run of flip-chip assemblies. I'm >looking for some insight on how best to underfill these parts. Is manual >equipment sufficient to do this? Any input as to materials & methods would >be appreciated. > >Thanks in advance, > > >Rick Thompson >Ventura Electronics Assembly >2655 Park Center Dr. >Simi Valley, CA 93065 > >+1 (805) 584-9858 x-304 voice >+1 (805) 584-1529 fax >[log in to unmask] > >--------------------------------------------------------------------------- ------ >Technet Mail List provided as a free service by IPC using LISTSERV 1.8d >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 delivery of Technet send the following message: SET Technet NOMAIL >Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 ---------------------------------------------------------------------------------