you win some! (and sometimes you don't...)

here is a microscopic visual journey of the attempted repair of a blunt force damaged touch IC chip on an iphone 4S. once we found that a replacement front assembly did not solve the problem, we began to dig a little bit deeper… resulting in a bunch of work that did not result in a successful repair. but it should illustrate some of the lengths we go through to help find a solution for our valued customers. sometimes there is no other way to attempt a solution than to venture along the process of the the repair. in this field, in the process of discovering the what is wrong and diagnosing the issue, you are sometimes well on your way to having completed the repair. or in this case, a repair was not possible and that we didn’t find out until we had completed most of the work needed to fully diagnose it. the full problem didn’t show it’s ugly head until the very end.

i got a call about an older unit that had experienced a hard impact – hard. i think the actual description was that it had been thrown. the screen was partially blacked out and the touch was not responding. not an unusual thing for a damaged unit, so we met and began to work on the phone. we always test a part before installing (learned the hard way) and when we fired up the unit, we got a very clear image, but when we went to test the touch, it was still not responding. hmmmm.

so we put on another front assembly, thinking that the replacement part may have been defective, but found the 2nd assembly acted just like the first. hmmmmm again – not a good sign.

i contacted the owner and gave them an update and told them that i would like to dig deeper and this may take a bit of time. so i headed back to the shop and began to look at the area related to touch on the motherboard.

after disassembling the device, and removing the motherboard, the first thing i noticed was that the motherboard was no longer flat. as you can see from the photo, the top area where the touch connector and the touch IC are located was slightly curved.

the connectors on the top side appeared to be ok, so we turned the motherboard over to examine the area where the touch IC is located and looked a bit closer.

the area is covered by shielding, but there is a hole on the top (see above photo), and if we angled the light and used our microscope, we could juuuust peak inside and sure enough, a crack on the touch IC…

so… the next step would be to see if we had a replacement touch IC and attempt to remove the damaged one and replace it with a “new” one. we start by heating up the shielding to remove it from the motherboard. the shielding is soldered on, but comes off with some patience. now we can get a real good look at the damaged component.

the cracked black square you are looking at (in the above photo) is the touch IC. also known as a BGA chip, or Board Grid Array. it’s like an upside down box of chocolates with the chocolate melted to the motherboard. this actual chip has 63 “chocolates” in rows of 8 by 8 minus 1 or 63. the chip itself is an array of connections with 63 endpoints of “chocolate” – which is actually points or blobs of solder that connect the chip to the 63 endpoints (pads) on the motherboard.

the removal process involves very high heat and we begin by shielding the other components as best we can with a removable pink heat shield.

when soldering and especially solder very small components on expensive electronics, you have to be very calm and kind of go into high focus (i think of words like “zen out” or “become centered” – you know, the kind of yoga lingo you hear about) because of the intense amount of concentration needed when working under a microscope. if distracted, one can easily end up causing additional, unnecessary work, or even ultimately help push the job into an unrepairable state. for me, having a good stereo microscope, the normal shakiness we all can exhibit when working with tiny things seems to come under control once i can see the tips of my tools in the view finder. it’s as if i’ve entered into that tiny world and i am better able to control my giant fingers and tools. it’s a weird feeling, but kind of addictive and cool too.

the chip has to be heated to the point that the 63 “chocolate” solder points on the bottom become liquid and the chip will lift with no effort and no damage to the 63 pads on the motherboard below.

success!!! but wait…. oh no…. after taking a closer look, i can see that the pads underneath on the motherboard are not as they should be. 7 of the 63 pads are missing (no shiny solder to greet my eyes). the impact that the phone experienced had not only cracked the chip, but in the process, had taken some pads along with it. those pads are really just delicate minute copper trace endpoints – sort of like delicate gold leaf foil for example. for a comparison, you can see in the photo below, the replacement chip that we had removed from a donor board that was waiting for it’s new home. you can see all 63 shiny globs of solder on both the chip and the pads on the motherboard it was removed from.