Hello Sunil, The limitations of X-Ray for opens testing is fairly well known. Shorts Show up completely obvious, opens are a bit more subjective - the operator (even 3D x-ray) has to decide if the shape is not what it should be. But, Opens can still exist when the ball maintains a spherical shape but has A high-resistive connection. This one area that, my favorite standard, IEEE 1149.1 adds value in electrically testing the connections for BGAs. I may be a bit biased as I have chaired the standard since 1996. Some of you may know it as JTAG which is the slang name. Software tools exist to generate Test patterns automatically without the need for 'domain expertise' in the system under test or the need to write/embed functional software code. The other advantage is that because the tests are algorithmic/mathematical, diagnostics are generated automatically from diagnostic engines to pinpoint exactly the ball that is failing. That goes a long way in improving the process when you know which ball is giving you trouble. There is an add-on to IEEE 1149.1 called 1149.6 which tests for stuck-ats on AC coupled nets Which you typically would find on SERDES. This standard is sometimes called ACJTAG but it is a bit of a misnomer as there is no at-speed test - it's not AC parametric but AC coupled. The 1149.6 support has to be designed in, and unfortunately some devices like a Xilinx V5 Do not support 1149.6 correctly - so at-speed JTAG test is all that is available for those Solder balls. SERDES BER through JTAG is done, however there is currently no IEEE standard, There are commercial products that let you execute and embed SERDES BER tests. What's interesting is that there are assumptions that at 25 degrees Celsius if a ball is good at X-ray it is good across all temps and all board flexing despite the properties of the materials having different coefficients of thermal expansion. Plug a board into a system, next To other boards and there is heat, humidity differences. So during system builds Or in the field new mysterious failures can occur. IEEE 1149.1/JTAG test can easily be embedded today with a $10 IC which can run these interconnect tests (and other at-speed tests like SERDES BER, DDR MemoryBIST, ASIC BIST etc) and record/log the failures to further drill into failure analysis - and avoid the no-trouble-found when the board gets back to depot repair. Some areas that need improvement: The standard doesn't enable this test for Power and Ground Pins directly. There are many indirect ways, especially with FPGAs to test that all the power/gnd pins are connected but it's not built into the IEEE standard itself. I currently have a working group that is looking at what can be done in this area. There are some Deficiencies on self-monitoring low voltage pins, which we are looking at as well. I hope this info helps. Maybe a little off-topic for SI but related. Regards, CJ *^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^* Lower your electronic product cost with Intellitech and Standards CJ Clark PH:603-868-7116 x115 Intellitech Corporation FX:603-868-7119 70 Main Street cclark(at)Intellitech()com Durham, NH 03824 http://www.intellitech.com *^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^* -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of sunil bharadwaz Sent: Thursday, December 03, 2009 8:13 AM To: SI LIST Subject: [SI-LIST] BGA Soldering Hi Experts , While trying to solder some LGA's , we are seeing some strange issues.The XRAYS & the Die penetration test reveal the Soldering is Okay.However , the performance of the board reveals that there is a soldering issue.When we replace the LGA with another chip , the board works fine.Of course even the original LGA works fine when re soldered on some other board. I guess the XRAY & the Die penetration test cannot be 100 % conclusive regarding the Soldering quality. Is there any way to establish the soldering quality authentically.I mean to say are there any better tests ? Thanks in Advance. Regards Sunil Bharadwaz ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu