Reballing to reuse BGA microcontrollers. - Page 1
Forum section: electronics / general

author: luiHS
author_rank: Frequent Contributor
timestamp: November 01, 2022, 12:14:40 am
content: Is it possible to reuse BGA microcontrollers, doing reballing or similar, what tools would I need?Until now I have worked everything with LQFP, but I have already started using BGA. Before, with the LQFPs, reusing chips from old boards was very easy, just take the chips out using the hot air soldering iron and solder them onto new boards.With BGAs, I don't know how to reuse chips from one board to another. Removing the chip is easy, also using the hot air soldering iron, but the tin balls of the chip to be reused are lost and something similar to reballing would have to be done, I guess.In case I can do reballing, I guess I'll need a steel template and some kind of support to hold and align the microcontroller with the template. And to place new tin balls, I saw some videos on YouTube using paste tin or balls that are already sold for reballing.Does anyone have experience in these tasks, and can you recommend what tools to buy?

author: luiHS
author_rank: Frequent Contributor
timestamp: November 01, 2022, 01:18:49 am
content: Searching through Amazon, I found these little reballing tools. They hold the chip and template to apply balls or paste tin.What I didn't find are BGA templates with pitch of 0.8mm and 1mm, and size 80*80 or 90*90mm that these tools require. So I thought about ordering a stencil from JLCPCB creating a circuit with just the chips, and then cutting the stencil to the required size here, but luckily it seems that JLCPCB can make stencils without a framework to a custom size by the user, in my case 80* 80 or 90*90mm.Unless there are other tools or better ways to do it, I think I found the solution to reuse BGA microcontrollers. Since they are very expensive and in short supply, it is important for me to be able to reuse them when I build prototypes.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 01, 2022, 01:20:14 am
content: It heavily depends on your target. DIY, Pro use? Ocassional or frequent?For DIY ocassional use, get a cheap kit from AliExpress.https://a.aliexpress.com/_EwJgZWdPretty messy, make something to keep balls under control.More expensive, also much tidier and easier to work with:https://a.aliexpress.com/_EuJ6YNXUse a good flux! Avoid Kingbo brand at all costs, some Amtech copies are good, look for those with clear or pale colour, those more yellowish are basically Kingbo stuff, very messy!Get a decent desoldering wick, I recommend Chem-wik brand on eBay.

author: luiHS
author_rank: Frequent Contributor
timestamp: November 01, 2022, 02:21:40 am
content: Quote from: DavidAlfa on November 01, 2022, 01:20:14 amIt is for professional use, although I expect to only have to use it occasionally, basically to recover and reuse microcontrollers from the prototypes I build. Right now for the RT1064 and STM32H7 these are very expensive and out of stock so I want to be able to reuse them.I just bought this tool on Amazon, it's the same one from Aliexpress, but it costs the same, or less because the shipping cost is included, and they ship from Spain (savings on customs fees and expensive shipping from China).https://www.amazon.es/gp/product/B08L9518WW/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1As the stencils would have to be customized for me at JLCPB, I only have the doubt as to whether, being made of steel, they could be used for reballing. I think that the reballing ones are made of aluminium, I understand that so that the tin does not remain welded to the stencil when heated with the hot air soldering iron.The problem is that the stencils they sell for reballing seem to be for large processors with very fine pitches, such as those for game consoles and mobile phones. So I thought of making my own stencils by ordering them from JLCPCB.

author: Psi
author_rank: Super Contributor
timestamp: November 01, 2022, 06:49:17 am
content: If you want to use solder paste to make the balls using the stencil then a DIY stencil will need to be fine tuned to find the right hole size/thickness etc..Probably better to use pre-made balls if you are going down a DIY laser cut stencil path.Like everything there is a skill component to it. It takes a while to get good at it.But it's very doable, just annoying and takes time.Watch Louis Rossmann or Paul Daniels SMC reball videos on youtube to see how its done in the repair industry when time is short.

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: November 01, 2022, 08:27:56 am
content: luiHS, I'm in the same situation, I have bought the blue fixture, and some tin balls, the problem with the balls is that they are very slippery and move around easily, so I could not even make a successful reball after trying about 30 times, I’m using chines Amtech flux, Now I'm ordering some solder paste to try that route, I hope it would be easier, if you find some useful paths please share.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 01, 2022, 11:30:59 am
content: The technique is simple:- Clean the MCU pads thorougly with copper braid and some flux until there's no solder left.- Clean cpu and stencil with alcohol and a brush, ensure there's absolutely no dirt.- Apply an almost invisible layer of flux to cpu, so it looks shiny, nothing else. Applying too much will cause boiling and throw/move the balls away.- Put the stencil over the CPU and align. Avoid wiping the flux, also don't wait for too long or the flux will dry out.- Drop the balls, remove the excess, then give it a shot of hot air at ~350ºC (With the stencil in-place) shouldn't take more than 10s, you'll clearly see how all the balls become shiny and self-align in their pads.- Remove the heat, don't move it for ~20 seconds, let it cool some!- While still warm, apply some drops of alcohol to loosen any flux that coulf be glueing the cpu and the stencil.- Carefully remove the stencil. I not coming off easily, it's usully the flux, warm it slighly with hot air to about 70ºC and apply more alcohol, try removing while still wet, this usually does the trick.- Apply a bit of flux and melt again, now without the stencil, to ensure all balls get perfectly aligned and soldered.- Of course you'll break few things before getting the skills. My advice is to practice with old useless crap first!The really hard BGAs are those going under 0.4mm ball size.Repaired my TV moths ago, replacing eMMC, those 0.3mm balls were a messy job!Some pics:

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: November 01, 2022, 12:04:33 pm
content: Thanks david for sharing, But the pics are missing, it would help a lot if you could post some vidoes too.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 01, 2022, 12:05:51 pm
content: The're tons of videos on YT, just find some!

author: NorthGuy
author_rank: Super Contributor
timestamp: November 01, 2022, 01:38:13 pm
content: I re-used few FPGAs for prototying - for example if the board is bad and I need to move to newer board without using new FPGA.I just tin both the footprint and the bottom of the BGA with solder, then I clean, add some flux, put the BGA in place, and use hot air.This is easier and faster than re-balling, but I only use it for prototyping - I wouldn't sell such re-worked product to anyone.

author: luiHS
author_rank: Frequent Contributor
timestamp: November 01, 2022, 06:31:18 pm
content: Quote from: NorthGuy on November 01, 2022, 01:38:13 pmI have thought of trying something similar, to avoid reballing, but in my case it is about new boards to which I apply solder paste to the entire board with a stencil and place the components with a pick and place machine.So I don't see the need for the BGAs to have balls, I could take the BGA I want to reuse from another board, remove the traces of tin until it is completely smooth and clean and place it on the new board where there is already solder paste on all the pads. I put the board to solder in the oven.I think this would be useful on new boards, where there is no component yet because that is how I apply solder paste to the entire board with a stencil. It would be different to put that reused BGA on a board that already has components installed, in that case I would not be able to apply solder paste with a stecil to the BGA pads on the PCB and I would have to reball the chip.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 01, 2022, 07:29:49 pm
content: Unless one side is completely flat, it'll be impossible to align, have you ever tried to put a ball on top of another?This is the same! It will slide for sure!Anyways, tinning won't put enough solder, also pads won't have the same amount, that's a big no for BGA.Maybe for a small 3x3 BGA, but definitely no for 10x10 or lager.

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 01, 2022, 07:46:16 pm
content: Is it for personal use or prototypes, or for any kind of production?For the former it may be acceptable depending on how much you value your own time - which admittedly can be elastic if you have no choice due to unavailability of chips - but for production? Not really.Now some companies can do that for you with all required equipment and skills. It's not cheap.

author: NorthGuy
author_rank: Super Contributor
timestamp: November 01, 2022, 08:08:47 pm
content: Quote from: DavidAlfa on November 01, 2022, 07:29:49 pmI did that few times. You don't have to be very precise in positioning. Once the solder melts the BGA moves into place. I did it with 256-ball and 484-ball FPGAs (1 mm pitch) and 169-ball PIC32MZ (0.8 mm pitch). I would expect it to be harder with smaller parts, but I haven't tried.Of course you get less solder than you would with balls. But it works.I guess solder paste on the bottom and tinned FPGA would work even better, but there's no way you can get as much solder as with balls.

author: brichards42
author_rank: Contributor
timestamp: November 01, 2022, 08:16:30 pm
content: Peter of TRX Lab (youtube) just put up a interesting video on reballing using a little hotplate, it's toward the end of the video.

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 01, 2022, 08:18:12 pm
content: Quote from: NorthGuy on November 01, 2022, 08:08:47 pmThat could work, but I think the headaches are likely. With no balls, the amount of solder is very likely to be uneven across all pads and thus the probability of some pads ending up not soldered due to a difference in height is high. I would personally not inflict that potential pain on myself unless I had no choice at all. Debugging bad connections on BGA pads is a nightmare.

author: abyrvalg
author_rank: Frequent Contributor
timestamp: November 01, 2022, 11:13:09 pm
content: Depending on how often you need this it could be easier to pay some local phone repair shop technician to do that for you, those guys do fine pitch reballs almost daily (for modest salaries). PM me if you need such contacts in Madrid or Barcelona.