I use a high-speed Dremel drill. However, here is another free tip: You can purchase the Dremel drill STAND for about $35 at any Menards, Lowes, Home Depot, or other large home and building store. Mount the drill into the stand (firmly) and bring the drill bit down so it is just touching the board surface, then screw down the stop adjustment until it stops the drill just at the surface when you rotate the Z-axis handle. Make sure the drill bit is clamped very firmly in the chuck. From there, if my ancient memory serves me correctly, for each full turn of the stop adjustment you will increase the drill penetration exactly .030". So if you turn the stop adjustment 2.5 turns, you will drill down .075", which is the thickness of the standard .062" PWB plus .015" into the solder joint. This is just an example. Please double check the amount of z-axis displacement with your drill stand before you try this. It is easy enough to determine. I scribed a line on my stop adjustment so I can see exactly where I am. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey (EHCOE) Sent: Tuesday, February 13, 2007 8:01 AM To: [log in to unmask] Subject: Re: [TN] FW: Report from a BGA And you learned about this from word of mouth. Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke Sent: Monday, February 12, 2007 4:34 PM To: [log in to unmask] Subject: Re: [TN] FW: Report from a BGA Yes I know the drill - it is a very small one..........8-) I have carried out that type of profiling many many times. I have found that the best type of drill to use is actually a dental drill and hand piece. What do other people use out of interest? John John Burke (408) 515 4992 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey Sent: Monday, February 12, 2007 1:39 PM To: [log in to unmask] Subject: Re: [TN] FW: Report from a BGA We operate with the kind of knowledge that Richard and Werner have shared along with the experience of measuring many different kinds of assemblies, materials, with different methods of thermal transfer and tools. When we get the luxury of following the "correct" way of checking a board we also run thermal couples under parts, taped to the part, and taped to the board to learn how these materials respond to our machines and process methods. Then we make educated guesses, based on experience. You know the drill. Starting March 1, 2007 New Location Guy Ramsey R&D Assembly 1660 East Race Street Allentown PA 18109-9580 (610) 264-1887 FAX (610) 264-1877 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory Sent: Monday, February 12, 2007 4:09 PM To: [log in to unmask] Subject: Re: [TN] FW: Report from a BGA What about us CEM's that rarely have the luxury of a spare bare board, or spare BGA's that we can play with? Sometimes we can convince our customers that we should have a spare PCB and BGA's to be able to properly set up a reflow profile, but most of the time we can't. What I do in that case, is to try and find a scrap PCB that might be close to the same thermal mass, and then I have some failed BGA's that have been pulled off a board from rework, and just lay them over top of my thermocouples, then do my plot. I know it's not exact, but it's the best I can do sometimes. I just try to ensure that I hit a high enough peak and stay liquidous for a decent amount of time. -Steve Gregory- -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D. Sent: Monday, February 12, 2007 2:56 PM To: [log in to unmask] Subject: Re: [TN] FW: Report from a BGA Werner, thank you for your note. I totally agree. I misread Inge's original email. I thought he said putting a thermocouple on top of the SOLDER PAD was misleading. What he actually said was putting a thermocouple on top of the component body was misleading. That is true. Another note. I totally agree the best way to thermocouple a profile test board is to drill up into the solder joint, insert the TC from the bottom so the weld is inside the solder ball. However, I then backfill the hole with thermally conductive epoxy with a minimum thermal conductivity of 14 BTU/in. hr. F. This helps reduce the insulative effect of the PWB just below the weld inside the hole. After the thermally conductive epoxy is cured, I then measure the electrical resistance of each of the thermocouple wires to the solderball via. I should get less than 1 ohm. If I do, then I know that the weld is making full mechanical contact with the inside of the solderball and/or the pad. When the mole or data recorder runs through the reflow oven, and I see a very solid line on the graph, I know I am measuring the actual temperature of the solderball/pad mechanical junction. If the profile line is not a solid line throughout, but is "noisy" with little spikes in both directions, then I know I am only measuring air temperature under the BGA, and I disregard that particular reading. The attenuating effect of full metal contact is easily seen. Incidentially, I recently wanted to verify that a small bake oven was getting a particular subassembly up to a certain temperature in a pre-baking operation. When I suspended thermocouples around the component within the chamber (measuring the air temperature), the 4 thermocouples measuring the air temperature consistently measured 6 degrees C. less than the 5 thermocouples that I had embedded into the subassembly using the method I just described. This was long after all of the TC readings had flatlined. The calibration lab questioned as to how an object being warmed by the air currents inside the oven could be hotter than the air currents themselves. The only explanation I could offer is that the thermal transfer efficiency of air directly to a thermocouple weld is less efficient than a piece of metal heated by the air making direct contact with the weld. I proved this by taking the thermocouples measuring the air and switching them with the thermocouples measuring the subassembly. The measurements were exchanged, one for one. Again, the TCs measuring air were all exactly 6 or 7 degrees cooler than those embedded in the assembly. I then took one of the TCs measuring air and clamped it to the metal rack in the oven. It went up 6 degrees. The same phenomena holds true for a thermocouple weld sitting just above a BGA pad, measuring air temperature alone. I notice it always measures a few degrees cooler than a TC with a good mechanical attachment to the solder or the pad, even when the solder is in liquidus. ________________________________ From: [log in to unmask] [mailto:[log in to unmask]] Sent: Monday, February 12, 2007 1:30 PM To: Stadem, Richard D.; [log in to unmask] Subject: Re: [TN] FW: Report from a BGA Hi Richard, Ingemar is absolutely correctthe only way you know what the t's are at the solder balls is to put thermocouples in them. It is indeed standar5d procedure see IPC-7530, 7.9.5. BGA solder balls get heated by conduction through the PCBmany people do not realize thisand BGA component body is in fact a heat sink and a shield preventing both convection and radiation heat transfer. Regards, Werner Engelmaier ????? Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 386-437-8747, Cell: 386-316-5904 Werner Engelmaier --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------