Hi TechNet! Just wanted to say thanks to everyone for the suggestions you generated concerning my cracking resistor question. And here is "the rest of the story"! I was able to successfully solder the chip resistors using a reflow solder process. I am guessing the problem was a solder process/material incompatibility. The flexural strength of the three materials is Al2O3 = 80 ksi, BeO = 30 ksi, AlN = 50 ksi (sorry Steve - I am metrically impaired so I switched everything to ksi!) covering a pretty wide range. The reflow soldering process allowed both terminations to "float" in a uniform manner when the solder solidified thus creating a much more uniform stress impact on the resistor. The hand soldering operation was most likely putting a larger stress on the resistor due to the independent solidification of the terminations. We are also going to try Vapor Phase soldering to see if we can repeat our success. Thanks again for the assist! Dave Hillman Rockwell Collins [log in to unmask] "Creswick, Steven" <[log in to unmask]> on 04/16/2002 11:44:09 AM To: "'TechNet E-Mail Forum.'" <[log in to unmask]>, "[log in to unmask]" <[log in to unmask]> cc: Subject: RE: [TN] Cracking Chip Resistors Dave, As I recall AlN (4-4.5 ppm) has a lower TCE than either Alumina (7 ppm) or Beo (7.2-8ppm) at soldering temperatures. One would expect that as the PWB contracted during cooling (having a still greater TCE), that the resistor would be in compression - not a problem here! Is the contraction of the individual solder joints sufficient to crack the body?? I looked in my records but wouldn't you know it, I am missing tensile strength info for AlN. But, yes it is weaker than Alumina. Al2O3 - 0.193 GPa, BeO - 0.062-0.069GPa, AlN - ? Flexural Strength - Al2O3 - 0.274-0.4 GPa, BeO - 0.110 GPa, AlN - 0.25-0.32 GPa Got me baffled as well. Never soldered BeO or AlN chip resistors - sorry. Guess I need to down another Vernors Ginger Ale! Steven Creswick - Gentex Corp -----Original Message----- From: Dave Hillman [mailto:[log in to unmask]] Sent: Tuesday, April 16, 2002 10:28 AM To: [log in to unmask] Subject: [TN] Cracking Chip Resistors Hi folks! I have ran into a problem which has me baffled and the extra 20 ounces of Coke I consumed this morning didn't bring about any better thought clarity so I would like to bounce the problem off the minds of TechNet. I have been attempting to hand solder a chip resistor (50 x 100) but have immediate cracking of the resistor across the width of the component. The resistor is either Aluminum Nitride or BeO (I'm still trying to find out which material). And yes, we are using proper soldering technique(s) and the resistor pad geometries are our standard dimensions. I know that the typical resistor body material is Alumina. Has anyone had good or bad experiences in hand soldering AlN or BeO resistors? Have I run into a material flexural strength issue? Dave Hillman Rockwell Collins [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 e-mail to [log in to unmask]: SET Technet NOMAIL 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 1.8d 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 e-mail to [log in to unmask]: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------