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 skills
I 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.
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