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I’m attempting first audio IC repair.
Curious what type of jumper wire to the pads that people use. Size? Is insulated better? If so does the wire need any pre prep or tinning beforehand. Apologies if this is too basic a question.
I currently have .01mm insulated and .02mm bare copper.
Thanks
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Insulated enamel wire requires pre-tinning as you need to scratch off the enamel coating which is non-conductive. In a pinch you can use for example the copper / magnesium wire from a earpiece speaker if you wanted.
Doesn’t have to be the same size of the pad it could be smaller or half the size. Larger jumper wires are only required for high power circuit traces / connections.
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Thanks for responding.
I also have un-insulated .02mm copper wire. Would this be easier to use (no scratching required)? Or will the trace be too vulnerable for shorting on the underside of the chip during reflow? Appreciate your comments. Thanks.
Insulated is recommended for long distance jumper wires because there is a high chance of touching other SMD components along the way.
For very short distance either one is fine you'll need to be careful lining / aligning the two ends of the jumper wires to the pads, pin or via it's being connected to.
To add to Ben's answer you will need spaghetti tubing or UV board patch to create an insulated (isolated) covering on the runs. for any lines longer than an inch you should raise the gage. And try to follow the original pathway as best as you can.
Thanks for your experience guys, this is a great help.
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If you are just running the C12 jumper the gauge wire will not matter as it is only a data line. I don’t use anything bigger than 0.02 I know the smaller gauge is harder to work with but you want the chip sitting as flush as possible. On this repair it doesn’t matter if it is insulated or not. I prefer insulated.
As for using soldering mask just make sure it doesn’t impact the chip area or the chip will not sit flush.
If the C12 pad has come off don’t just use a straight wire, make a pad with the wire by forming a circle.
It is a good idea to re-ball the IC with leaded solder and use a pre-heater when putting the IC on to avoid heating the baseband CPU to much.
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Thanks so much for this informed answer it is very helpful indeed. As this is a very delicate job for me first up and I don't want to screw up, at the risk of sounding anal, just a couple more questions.
Am I correct in saying that the underside of the audio chip itself is a ground plane with individual pads isolated? If so, then an uninsulated bare wire going to a pad (eg C12) on logic board could have a chance of shorting against the chip when it is put back on?
For insulated wire, how do you prepare it. Please explain if, and how you do the scratching and tinning if that is required first. It is generous of people like you to share with us noobs. Many thanks.
Insulated wire you scrape the wire with soldering iron to get rid of the enamel coating where you want to tin the wire (only need to scrape the ends where you are soldering on) then once the solder starts to get on the wire it is ready to be used as a jumper wire.
@jeffo1 The underside of the chip is not a ground plain. The ground is on individual balls. If you do have a ground plain you have damaged the chip and it will need to be replaced.
Remember these chips are like glass be careful when handling them, if you see a nick from tweezers it is best to get another chip.
Like Ben said I use my hot tweezers to remove the enamel.
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