Replace miniature SMD component on HackRF One: which technique - Page 1
Forum section: electronics / repair

author: Bicurico
author_rank: Super Contributor
timestamp: December 07, 2023, 07:13:24 pm
content: Hi,I need to replace the amplifier on the RF input, responsible for RX.This is a common fault, here is more about it and a picture of the PCB. In my case it is the one blue arrow.https://github.com/greatscottgadgets/hackrf/issues/901I have an Aeyoue hot air soldering station, but little real experience.Before I just try my best, I thought to ask here how you would do it.Using hot air is difficult because there are many other small components next to it.This makes it tempting to just try to use the tip of the soldering iron and lift the IC. But I know this might botch the traces and burn the PCB.The next question is: how to solder the new one? I have seen videos, but I don't even have this flux paste that makes it look so easy.Any tips are welcome.

author: Bicurico
author_rank: Super Contributor
timestamp: December 10, 2023, 05:54:38 pm
content: Since nobody replied, I add some info:The one I need to replace is the one with the blue arrow.It's a MGA-81563 and it is tiny... Here a link to the datasheet:https://www.farnell.com/datasheets/7246.pdfAgain, the question is simple: How would you replace the broken one on the PCB with a new one?Would you try to use a hot air soldering station (at what settings - temperature and air flow)?Or would you try to remove it with a regular soldering iron?What is the best way to solder it back again? Using the hot air station or the soldering iron?Thanks,Vitor

author: Grandchuck
author_rank: Super Contributor
timestamp: December 10, 2023, 06:12:10 pm
content: Do you have liquid flux and solder wick?

author: Aheld
author_rank: Regular Contributor
timestamp: December 10, 2023, 06:15:49 pm
content: Hi,I would try to desolder with heat gun and soldering with iron pin by pin.If you have the possibility to preheat the PCB from bottom to 100deg would make it easier.Br. Axel

author: Bicurico
author_rank: Super Contributor
timestamp: December 10, 2023, 06:17:39 pm
content: I have liquid flux, but never used it. And I never had success with solder wick...

author: globoy
author_rank: Frequent Contributor
timestamp: December 10, 2023, 06:21:29 pm
content: I just made this repair. I used a hot air gun (pencil style tip, maybe 3-5mm in diameter) and a pair of tweezers to remove the damaged parts. I generally dial down the airflow so it won't blow parts around and at a lower setting the solder on parts surrounding the target may reflow but tension holds them in place.Then I used a fine solder wick that I pre-treat with flux to clean up the pads of the removed parts and clean them with isopropyl alcohol on a q-tip. I used a "standard" iron tip for this so it can deliver a fair bit of heat. Dab, don't shove the tip and solder wick around as you might tear up a small pad. Pull the solder wick up with the iron so it won't get stuck to the pad.Then I added solder to one pad, added a little flux to re-wet it and holding the part with tweezers in one hand to align it, soldered the part in place to that pad with a fine tip iron. Then soldered the remaining pins and cleaned up again with isopropyl alcohol on a q-tip.I use leaded solder and a Kester 2331-ZX flux pen.I'm pretty sure you could also use the hot air gun to solder the whole part at once. When I do that, I usually still clean off the old solder and then put a little new solder on each pad, add a little flux and then use the hot air gun with the part held by tweezers to solder it in place. Sometimes that works better for pads connected to a power plane since fine-tip irons may have a hard time making solder flow with that amount of heat-sinking.Good luck! It is too bad that this part of the Hack RF design is so fragile. I bought a set of 10 of these amplifier chips.

author: Grandchuck
author_rank: Super Contributor
timestamp: December 10, 2023, 06:28:08 pm
content: Solder wick that is old does not work as well. Anyway, you should be able to lift each side of the IC by heating the pins/pads on that side. Then clean the board using liquid flux and solder wick. Solder the new device by tacking two pins, on opposite sides. Then proceed to solder the rest. Don't worry about shorts now. After all are soldered, apply liquid flux and remove any solder bridges (shorts) by using a clean iron tip and dragging away from the IC. Inspect with lighted magnifier and then clean the area with alcohol.

author: rteodor
author_rank: Frequent Contributor
timestamp: December 10, 2023, 07:06:07 pm
content: I used kapton tape to hold nearby components in place while I was removing a QFN64 and the result was very clean.But I did this only a few times so YMMV.