Please do not torture TIC BGA chips with paint stripper heat guns ! - Page 1
Forum section: electronics / general

author: Fraser
author_rank: Super Contributor
timestamp: October 10, 2018, 02:23:36 pm
content: Just a quick post to detail the nightmare I face quite often when someone tries to repair their own thermal imaging camera without the correct knowledge or tools.Some background....Over the years there has been much written about certain types of chips used in computers that can suffer connection issues through age or overheating. NVidia and XBox 360 GPU chips come to mind. Various attempts have been made to 'repair' these BGA chips. Some use physical clamping to compress the chip whilst others use heat guns in an attempt to reflow the BGA solder balls. The problem with the chips is often more complex than the BGA solder balls and is related to special contact bumps that connect the Silicon Die to the BGA solder ball platform that is soldered to the PCB. No amount of heating will actually repair the issue as the bumps are not intended to melt at solder temperatures ! The heating and contraction can 'rectify' the issue for a while but it is not a long term repair in the true sense of the word. There has been lots written and spoken about this issue so I will not repeat it here. Needless to say BGA chips can be total pigs to rework in an effective manner.So why do I bring this matter to the thermal imaging forum ?Recently I have worked on several faulty thermal cameras that had been 'got at' by either their owners or incompetent repair techs. Why do I use the harsh term "incompetent" ? I use it because they almost destroyed a TIC through poor diagnostics and silly attempts to find a magic instant fix using a heat gun. I suspect in desperation rather than through any sensible thought processes. It may seem like I am using harsh words but the cameras involved were worth many thousands of Pounds, not some cheap PC motherboard !So what did these people do to the cameras ?1. Poor disassembly technique resulting in ripped FPC's, damaged locking clips on connectors. This is easily done and quite common. I expect such issues.2. Poor soldering technique on SMD components, in some cases causing solder bridges between pins.3. PCB's swimming in solder flux and lint from repair attempts.4. Melted connectors through inappropriate use of a hot air station or contact with a soldering iron barrel.5. Now the killer ..... cooking of the PCB using either some form of heat gun or a toaster oven !All of the above damage is unescessary but it is item 5 that is becoming worryingly common. There seems to be a view circulating that most faults on modern computer motherboards and embedded computers can be solved by heating either certain chips or the whole PCB to reflow them. Such a common cause of electronics failure has never been the case, and nothing has changed ! The issue with certain GPU's and 'bush engineering solutions' has 'infected' the repair processes being used by some people.I have so far seen two TIC PCB's totally destroyed by being placed in a toaster oven and Cooked to the point of destruction.....board warping and SMD component migration. The cameras were total write offs as the replacement PCB's were over $5K each.Other units I have worked on had more localised damage that I could rectify and return the cameras to service. One main PCB had been flooded with rosin flux before being placed in some sort of oven. It came out of the oven as a brown sticky mess and several SMD components has moved off of their designated pads. Cleaning off all the rosin flux was a PITA ! Other PCB'd show the tell tale signs of localised heat gun use on various chips, most commonly the BGA types, but also conventional leadless encapsulations. You know it is localised heating from the presence of flux around the part, discolouration of the PCB lacquer and most noticeable.... melting of the versions labels around the part but not in other areas of the PCB.Apart from the written off cooked PCB's I repaired the others and not one had a faulty solder joint associated with a chip ! The faults were mainly caused by the following.... power supply components, DRAM, MLC capacitors or glue Logic failure. Generalised heating was unnescessary in all cases.It has been a busy few weeks but I can say without hesitation, the most frustrating repairs have been those where someone already 'had a go' and I needed to reverse the damage they did before finding the original cause of failure. I am now considering refusing to look at units that are no longer Virgin's. Fixing other people's messes takes time and the owner generally does not like paying the extra time needed for such.So PLEASE do not be tempted to heat gun or toaster oven your valuable TIC PCB's or any PCB's for that matter. If you cannot track down a cause of failure with a decent degree of certainty, pass the job to someone who can. Cooking your PCB is highly unlikely to help matters.I know this is an unusual post for this area of the forum, and a moan, but it saddens me to see so many thermal cameras suffering this sort of unnescessary damage. I no longer repair people's FLIR One series cameras as I have seen too much owner induced damage and toaster oven victims ! The FLIR One series is just not worth the time needed to repair them.Fraser

author: railrun
author_rank: Regular Contributor
timestamp: October 10, 2018, 02:56:20 pm
content: If heat-gun can‘t fix it, nobody can fix it

author: Fraser
author_rank: Super Contributor
timestamp: October 10, 2018, 03:11:36 pm
content: What is amazing is the ability of some plastic cases chips to withstand the abuse from a high temperature heat gun. I have seen the chips tops actually melted and distorted, yet the chip still works ! It's life expectancy may have been reduced however.The heat gun/oven method may well be a 'last ditch' attempt at repair. Is that a fair approach to someone's valuable hardware though ? The heating method can most certainly be the death of a PCB making it BER for any other techs who look at it.Fraser

author: railrun
author_rank: Regular Contributor
timestamp: October 10, 2018, 04:54:32 pm
content: Thanks to Youtube many people believe it works. Louis Rossmann has a nice video (also on YT) about the truth of reballing BGA chips.

author: Fraser
author_rank: Super Contributor
timestamp: October 10, 2018, 06:13:34 pm
content: Indeed, Louis has done some excellent work explaining the issues surrounding the flip chip chip fault and how heat gunning or reflowing such a chip is not a true repair if the 'bump' contacts are the problem.Fraser

author: bap2703
author_rank: Regular Contributor
timestamp: October 11, 2018, 05:38:55 am
content: Can we get some pictures for entertainment ?

author: Fraser
author_rank: Super Contributor
timestamp: October 11, 2018, 09:03:32 am
content: The cameras are not mine and I would only make pictures of them public with the owners permission. Sorry.Fraser