AMD BGA Reball - Page 1
Forum section: electronics / general

author: SgtRock
author_rank: Unknown
timestamp: July 22, 2013, 11:22:39 pm
content: Greetings EEVBees:--I am trying to repair a Vizio M329SL LED LCD TV. The problem is a blown Mediatek MT5396CUFJ BGA ARM. It seems likely that the problem is Tin Whiskers shorting from ball to ball, so whether the chip is actually damaged or merely bridged, has yet to be determined. I have obtained from Alibaba a used one, which they took out of a working unit. It has leaded solder balls. I feel confident I can remove the leaded solder balls. But I need advice on a couple of issues:1) Determining the Pitch of the BGA ARM Chip. My measurements indicate (see picture) a pitch of 0.806 per mm. or an 0.8 pitch. Is this correct in your opinion? I am going to order stencils above and below this pitch, what range should I order. I do not mind ordering a few extras.2) I plan to remove the unleaded solder balls, using Sunbeam Frying Pan, and using a thermocouple to preheat to 150C, then applying flux and leaded solder, and without touching the chip gathering all of the solder into a blob using a Hakko 936 with a 908 iron and a hoof tip at approximately 250C, and following up with Goot 3mm Solder Braid, followed up by more flux and Q-Tips.3)The Bad ARM on the Main Board will be removed , shielding everything but the ARM Chip with aluminum tape and preheating the board to 150C. Then using hot air until the chip gets loose, the temperature will be gradually raised, until can be lifted using suction tweezers (at 210C-230C). The removed ARM Chip and the Main Board will be cleaned as in step 3) above.4) Then comes the real problem! I will need to reball the new (used and removed from a working unit) ARM BGA Chip, and with the unleaded solder balls removed and the chip spotlessly cleaned. Now we come the really difficult part of the operation: How to reball the chip. Alibaba has no source for a stencil or even a data sheet. My plan so far is to carefully apply Kingbo Reballing Flux only to the pads which are present, as best I can. Then to tape off, as far as possible the part of the stencil which does not have balls below. Then I will sprinkle the balls, remove the stencil, inspect, and correct any problems and attempt to melt and attach the balls, preheating the chip using the Sunbeam Frying Pan (150C), and using hot air from my Hakko 851 Hot Air Tool to heat up to melting and settling point. I will track the temperature using a thermocouple.--I have a couple of extra Main Boards, and have ordered a couple of extra ARM Chips, so that I may continue after I make a couple of destructive mistakes. So, it is not an all or nothing proposition. I am doing this as a learning project, and will not be upset if I destroy some parts by experimentation. What I really need is frank advice by people who have done this sort of thing.--I would like for all of you repair minded folks, that through hole is quickly disappearing for consumer goods, and that SMD and BGA are truely the Future."When the juice is t'drinkin' and the good times is t'jumpin'"Lord Buckley 1906 - 1960Best RegardsClear Ether

author: marshallh
author_rank: Unknown
timestamp: July 22, 2013, 11:41:09 pm
content: Keep the leaded balls on there. They were put on there on purpose, and reballing yourself is possible but takes a lot of headache.Yes, 0.8mm is common.Many ebay sellers sell reball jig kits with a colection of stencils that are cut specicifally for a particular chip ballout - CPUs, GPUs, etc. Try searching around for variants of your part number.Since your replacement was already reballed, your job is easy. You just need to lift off the old part, use quality wick to remove ALL solder, clean with isopropyl, and then reapply thick flux, place bga on the pads, and reflow.

author: SgtRock
author_rank: Unknown
timestamp: July 22, 2013, 11:57:40 pm
content: Dear Marshallh:--Thanks for your prompt reply. I should have said unleaded solder balls which need to be removed. I have since corrected the text to say unleaded rather than leaded. It is however a common mistake which I have seen before. The suspected problem with narrow pitch unleaded, high Tin content solder balls is Tin Whiskers. Hence, my need to clean and reball. I am sorry to have mislead you by my poor editing. So, I still need advice about reballing. Again I apologize for misleading you inadvertently."There are two possible outcomes: If the result confirms the hypothesis, then you've made a measurement. If the result is contrary to the hypothesis, then you've made a discovery."Enrico Fermi 1901 1954Best RegardsClear Ether

author: TerraHertz
author_rank: Super Contributor
timestamp: July 23, 2013, 11:55:50 am
content: Yet another victory for ROHS. Victory for planned obsolescence, that is.The idea of high-tin no-lead solder balls on a tiny scale like that. Complete madness. And no I flatly don't believe the people responsible never heard of tin whisker growth.