Soldering flex cable - tips & tricks

[Prott]

Hello fellow badcappers,
I have to solder a MacBook (A1708) screen flex - one of the two data flexes got slightly torn (2 broken traces). I've seen some videos on youtube where people scrub the coating and then simply apply flux and solder to the exposed copper traces (and then run a jumper wire). However no matter what I try the copper does not take the solder at all - the more flux I add the more it actually stays only on the iron itself.

I am practicing on a spare flex cable and it's gettiing quite annoying - to a point I am actually thinking I have to be doing something extremely wrong. Before the solder even sticks the whole cable melts

I am using a smallest tip (about the size of the small trace) at 400 C.

Can anybody more experienced please help?

[diif]

Re: Soldering flex cable - tips & tricks

I'd use a bigger tip, I think the small one can't get any heat into the trace.

[dellxps15]

Re: Soldering flex cable - tips & tricks

are u sure u scraped the right side of the copper ?

[spidertnt]

Re: Soldering flex cable - tips & tricks

https://www.youtube.com/watch?v=5nBiN8Uujlw&t=29s

[Prott]

Re: Soldering flex cable - tips & tricks

Thanks. Yes, I've seen that video, but for me the solder just doesn't stick at all.

are u sure u scraped the right side of the copper ?

For a moment I got worried, but checked on a spare cable and yes, it seems to be a correct side of the cable (there's nothing from the other one).

I also tried to use the bigger tip, but still nothing. If I keep the heat on for too long it just burns through. :/

[mcplslg123]

Re: Soldering flex cable - tips & tricks

as @dellxps15 has already pointed out, i still think you are scraping the opposite side of the cable.It doesnt take much effort to put copper on the traces.Jumpering them is however very hard.

[dellxps15]

Re: Soldering flex cable - tips & tricks

never exceed melting solder temperature + 20° celsius . on my atten i use 360° otherwise cable will bend and broke apart.do some try on that spare cable first.
scrap them with a blade (i use blade only from glass cleaner scraping)
put cable in a perfect flat hard surface and scrap it opposute way from cutting blade to not cut the cable. u have to scrap not cut.
scrap untill the copper is shining. not shining means it has cover on it.

[Prott]

Re: Soldering flex cable - tips & tricks

Thank you. Will try that with a better blade, bigger tip and lower temperature. Do you think a low-melt solder would be better for this application?

mcplslg123 - I scraped on the opposite side of the spare cable and there are no traces visible in that part. Only thing I can think of is that the cable is multilayered - will test it.

[Prott]

Re: Soldering flex cable - tips & tricks

Upon further investigation it indeed seems as if that was the WRONG SIDE of the cable. Thank you!
However the break is in such place that it just might be easier and more reliable to remove the screen and replace the cable with a new one - even considering how brittle the screen is. Oh, why couldn't they use screws...

[petehall347]

Re: Soldering flex cable - tips & tricks

can you not use an extension cable ?

[dellxps15]

Re: Soldering flex cable - tips & tricks

to solder the new cable with wire u just need 2mm