Completely f*d up my first BGA job - Page 1
Forum section: electronics / beginners

author: soFPG
author_rank: Frequent Contributor
timestamp: June 11, 2021, 07:59:23 pm
content: I just completely messed up my first BGA soldering job (256 pin with 1mm pitch).At first the balls from the manufacturer (Xilinx FPGA) weren't reflowing and after they finally reflowed I got various short circuitsAfter doing some more reflowing, the errors remained and I completely removed the chip from the board. After removing all solder from PCB and chip I am now thinking about reballing the chip (but with lower temperature solder this time).The only problem is I don't have any equipment for it. Any recommendations what the minimum equipment would be?

author: Unixon
author_rank: Frequent Contributor
timestamp: June 11, 2021, 08:38:08 pm
content: What is this FPGA in question, is it expensive? If not I would try to tin pads equally instead of proper reballing and press the chip against the board in a sea of flux. This is bad, very bad method, but if there's no option to reball it properly...p.s. do you think these shorts are due to solder joints or something else?

author: JustMeHere
author_rank: Frequent Contributor
timestamp: June 11, 2021, 09:03:18 pm
content: I've seen videos where paste, hot air, and some of these make it look easy.https://www.amazon.com/dp/B07WHQP2CC/ref=cm_sw_r_cp_apa_glt_fabc_9Q63V4HC3N829AAJ27SK?_encoding=UTF8&psc=1Video:https://youtu.be/EjAdz8jQL4k

author: julian1
author_rank: Frequent Contributor
timestamp: June 11, 2021, 09:05:25 pm
content: Maybe the approach outlined here (I have not tried it). The key is to bead up the pcb pads as well as the bga pads. Then cleanup, reapply flux, and reflow.https://www.eevblog.com/forum/projects/0-65mm-bga-jlcpcb-hot-air!/msg3542934/#msg3542934

author: Manul
author_rank: Super Contributor
timestamp: June 11, 2021, 09:43:01 pm
content: I just wanted to share, that it is completely possible to do quality reball without stencil, solder balls or paste. This is a bit extreme, but when you need it done and there is no other option... Here is my reballing of 132 balls, 0.5mm pitch bga chip. I did it by cutting 132 equal pieces of 0.3mm solder wire with a razor, puting all pieces on a cleaned and fluxed IC and melted into balls with hot air. Totally not recommened, but possible.

author: jbeng
author_rank: Regular Contributor
timestamp: June 11, 2021, 09:50:40 pm
content: I heard about this product years ago, though I've never used it.It looks like a super easy way to do rework (or first work, if you will) using BGA-packaged components.Check out their product and a how-to video at this link:https://www.solder.net/products/stencilquik/

author: james_s
author_rank: Super Contributor
timestamp: June 11, 2021, 09:58:53 pm
content: I'd suggest getting a bunch of the cheapest BGA parts you can find and make a batch of practice PCBs with multiple footprints for that same part and then practice soldering them until you get the process down. It can get expensive real quick trying to learn by soldering something like FPGAs.

author: MathWizard
author_rank: Super Contributor
timestamp: June 11, 2021, 11:31:38 pm
content: Quote from: JustMeHere on June 11, 2021, 09:03:18 pmYeah I want to try to desolder some big processor's off old cable boxes/motherboards. But then I don't have any dies, or vices,/jig's/etc.I have an old GPU that something's fried on it. But I'm not sure my hotair gun is currently working either.

author: Electro Fan
author_rank: Super Contributor
timestamp: June 12, 2021, 05:36:18 am
content: Quote from: Manul on June 11, 2021, 09:43:01 pmImpressive. Nice work!

author: soFPG
author_rank: Frequent Contributor
timestamp: June 12, 2021, 10:05:17 am
content: Why is everyone even saying that BGAs are easier to solder than QFNs? I have no clue where the short is so I basically have to reball every time I get an error?

author: Fraser
author_rank: Super Contributor
timestamp: June 12, 2021, 11:31:32 am
content: soFPG,You have not detailed the equipment and process you used to solder the BGA chip.Key factors to success with BGA soldering are….. clean PCB pads, Plenty of good quality FLUX, correct alignment, decent quality tools to heat the BGA chip and a steady hand. If the correct process is followed the BGA chip can be relatively simple to solder but life gets a lot harder if you do not have a good quality sticky flux and a decent chip heating system. The BGA chip solder should flow and accurately locate the chip on the PCB pads. Solder bridges tend to be the result of poor chip initial alignment or exterior forces causing movement. There is no reason for solder to bridge adjacent pads if correctly aligned as decent FLUX creates the correct conditions for correct solder flow. While a gentle ‘nudge’ of the chip is permissible to check reflow and alignment, great care is needed as too much movement creates a solder bridge. The flux quality is very important for several reasons. It creates the correct conditions under the chip for good solder whetting and needs to be of a type that will not cause issues with residue left under the chip. Cheap or fake flux can be a disaster when it comes to BGA soldering. The correct flux is sticky when cool and turns to a thin liquid when heated. The sticky property helps to hold the chip in position when installed and heating is started.Regarding the equipment needed to solder a BGA chip……. There will be many different views on this ranging from a kitchen frying pan on the hob or a hot air paint stripper gun to a top of the range PACE BGA rework station costing many thousands of Dollars. Much depends upon the size of the chip, performance of the heating system and experience of the person doing the soldering. I personally believe that a beginner is ill advised to use sub standard heating methods as such can make the learning experience pretty frustrating. I bought a decent hot air station for general SMD rework but realised that large BGA chips need something more appropriate for the task. I bought a cheap Chinese Infrared BGA rework station for less than £100. That was a mistake in my experience. The station uses a ceramic bottom preheater and a halogen IR lamp as the top heater. It is crude but works if you are lucky. It is more than capable of destroying both the BGA chip and burning your PCB ! These cheap Chinese BGA rework stations are far from optimal and built down to a price. I quickly realised that frustration levels from using such a really cheap IR BGA rework station exceeded the saving made against the cost of something decent. I sought out and bought a Used Jovy 7500 dark IR BGA rework station and it is a joy to use. As I suspected, it is far easier for the beginner to learn the art of BGA soldering and rework if they have decent kit to work with. Otherwise the user of a lesser performance station can start to doubt their technique and skills when in fact the equipment is wanting on the performance front. The Jovy 7500 cost me £350 used but is in mint condition. For a decent BGA rework station that is actually pretty inexpensive !I am not suggesting that someone who only occasionally works with large BGA Chips should go out and buy an expensive IR or Hot Air rework station but it is food for thought. If you do not have the correct equipment for the task, you may face much frustration and failure before perfecting use of a less expensive BGA soldering or rework solution at lower cost. There are some good posts on converting toaster ovens for PCB soldering or upgrading of cheap Asia sourced SMT soldering ovens….. you do need to practice with those however as there remains a certain amount of user experience required for all soldering and reflow techniques.If you are doing very limited BGA soldering or rework you may get away with one of the sub £100 IR rework stations from China but be aware that the Halogen lamp has a life of around 20 hours….. yes 20 hours ! and can cost around £50 to purchase a new one. Ceramic dark IR emitters are also expensive at around £60 but they have a far greater life expectancy. A halogen lamp can fail after only a few hours, or even minutes of use ! BGA rework is commonly done with either Hot air or Infrared heating. SMD PCB creation is commonly done in a reflow oven or can be done with hot air or Infrared.As others have stated, it is good to practice with scrap parts. I bought a pile of obsolete laptop PCB’s and started practicing removal and refitting of BGA chips on those. A laptop PCB has multiple layers, high heat soak characteristics and quite dense component layout…. Perfect to hone your rework skillsI re-balled the removed BGA chips myself but would recommend buying new chips that are pre-balled whenever possible. I prefer installing solder balls of the correct size (using a stencil) to the solder paste and stencil technique.Good luck in your BGA soldering learning process. It can take some time to master but, given the correct tools, it is not that hard to achieve excellent results and reliability.For ‘one off’ or very occasional BGA work, it may make more sense to seek out someone local who has the correct equipment and get them to do the BGA soldering for you. Computer repair shops may own such equipment and may be willing to help, but it will likely be quite expensive due to the time needed for the task. I believe investment in a decent BGA rework station is an investment in the future as modern technology seems to demand such equipment more and more as BGA chips become more common in large numbers on PCB’s. You can always sell the rework station in the future if no longer needed.

author: Fraser
author_rank: Super Contributor
timestamp: June 12, 2021, 12:05:43 pm
content: The two IR rework stations that I own. The T862++ is a well known budget Halogen lamp based station intended for mobile phone rework but pretty unpredictable if you are not experienced in its use. The Jovy 7500 Dark IR Ceramic heater station is also made in China but to a much higher specification (apparently German) and offers excellent performance. Sadly Jovy went out of business so the stations are mainly available used. I imported mine to the UK from Poland.Do your research before buying an IR rework station ! There is a lot of junk out there !

author: soFPG
author_rank: Frequent Contributor
timestamp: June 12, 2021, 12:20:11 pm
content: Fraser, do you have a recommendation for good quality flux?

author: Fraser
author_rank: Super Contributor
timestamp: June 12, 2021, 02:52:38 pm
content: Genuine AMTECH sticky flux such as AMTECH NC-559-V2-TF is a well respected product but sadly it is often faked by Asian companies so be very careful who you buy it from ! Most of the stuff on eBay is fake. If it is a lot cheaper than normal retail suppliers, consider it fake. AMTECH is a USA product, not from China.Forum members in the USA can buy genuine AMTECH NC-559-V2-TF Flux from NorthridgeFIX or other bona-fide suppliers. NorthridgeFIX is an official agent for AMTECH and gets fresh batches suppplied to order. It is not cheap but then neither are the BGA chips or the time you waste with some fake fluxes that are imitating AMTECH but of poor performance.https://northridgefix.com/product/amtech-nc-559-v2-tf-flux-10g-syringe-plunger-2-needle-sizes/The AMTECH web site......https://amtechdirect.com/shop/AMTECH Tacky Flux listings... There are many Flux types to choose from and AMTECH are a trustworthy manufacturer of flux.https://amtechdirect.com/category/amtech-tacky-solder-flux/AMTECH NC-559-V2-V2-TF page .....https://amtechdirect.com/shop/amtech-nc-559-v2-tf-no-clean-tacky-solder-flux-with-uv-tracer-rol0-30cc-syringe/Fraser

author: Unixon
author_rank: Frequent Contributor
timestamp: June 12, 2021, 06:35:07 pm
content: Is there a cheaper alternative to AMTECH fluxes?These are OK for repairs, but too expensive for small scale production, a flux must be like 10 times cheaper at least to be acceptable for manufacturing.Do these fluxes leave any residue or stains on white solder mask?Many fluxes do when heated to temperatures near top of thermal profile, it's not a huge problem for dark solder mask but stains left on white solder mask just ruin the board.

author: Fraser
author_rank: Super Contributor
timestamp: June 12, 2021, 07:52:21 pm
content: Sorry I cannot comment on cheaper alternatives that work as well. The flux will turn brown if overheated.Others on the forum may have recommendations for production work as companies like Kester also produce good flux. Sadly it is sometimes necessary to spend the money on a good Flux product to ensure production reliabilty and avoid rework costs. I have used TOPNIK Flux from Termo Pasty of Poland and it it works well. They make different fluxes including no-clean types. I cannot comment on suitability for BGA work or production use however.https://termopasty.pl/en/kategorie/soldering-and-welding/

author: SilverSolder
author_rank: Super Contributor
timestamp: June 12, 2021, 11:36:31 pm
content: Quote from: Manul on June 11, 2021, 09:43:01 pmNice precision work.

author: mawyatt
author_rank: Super Contributor
timestamp: June 13, 2021, 01:32:55 am
content: Quote from: Fraser on June 12, 2021, 02:52:38 pmHave a project where we'll need to mount some 100 lead LQFP 14mm square packages and other usual SMD (0603, 8 pin SOIC) devices. Would the AMTECK Flux be a good choice for this type of use?Best,

author: Fraser
author_rank: Super Contributor
timestamp: June 13, 2021, 11:57:30 am
content: The AMTECH tacky flux is great for many soldering applications but I am a little confused as to why you want to use it for conventional passives and small IC’s in production unless you are using a hand soldering technique. In production situations passives and non BGA IC’s are normally soldered with solder paste that contains both tiny solder balls and sticky flux. No real need to add additional flux. If hand soldering passives and IC’s using either the pre-tinning of pads or direct solder application on a soldering iron tip…. then yes, the AMTECH flux works well to help the solder flow on the PCB pad and component lead/contact. In repair circles it is common to remove a component, clean the PCB pads, apply good Flux, position the new component on the pads and solder it with a soldering iron that is pre loaded with solder that transfers across to the pad and component. Hot air rework can be used on PCB pads that are pre loaded with some fresh solder and then Flux applied to aid flow and wetting before the heat is applied for solder reflow.So basically, AMTECH, or any decent Flux, is great to aid solder wetting and flow but not normally applied if good solder paste is being used.Fraser

author: mawyatt
author_rank: Super Contributor
timestamp: June 13, 2021, 02:47:44 pm
content: Thanks.This is not a production run, but a prototype, although has 12 complex PCBs all with many SMD. I've never attempted mounting a large pin count LQFP device before and after watching a few videos the hand soldering technique seemed best approach, rather than using a stencil and solder paste. The components cost well over $2K, so don't want to mess things upAny advise is appreciated.Best,