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Go Back   GSM-Forum > GSM & CDMA Phones / Tablets Software & Hardware Area > iPhone ,iPod & iPad (Apple Inc. Products) > iPhone, iPad, iPod Hardware Repair

iPhone, iPad, iPod Hardware Repair Hardware Repair discussions for iPhone, iPod , iPad & Apple Products, help, guides.

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Old 08-01-2017, 06:22   #1 (permalink)
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U1700 with missing pads


Hi guys, got this iphone 6 with U1700 desoldered, with some ripped pads that need to be rebuilt.
The missing pads are:
B3 - USB0_DN that goes to 90_AP_BI_TRISTAR_USB0_N
C2 - BRICK_ID that goes to TRISTAR_TO_PMU_USB_BRICKID
D3 - SDA that goes to AP_BI_I2C0_SDA
D4 - SCL that goes to AP_TO_I2C0_SCL
E2 - UART0_TX that goes to AP_TO_TRISTAR_ACC_UART6_TXD (directly under the CPU)
E4 - SWITCH_EN that goes to RESET_1V8_L
Are all these pads necessary? It's quite difficult to rebuild those pads, because there aren't visible routes, they all go under the top layer.
Advices? Thanks
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Old 08-03-2017, 17:02   #2 (permalink)
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You pulled out too many pads mate, some of them are necessary. So you need to rebuild the pads with jumpers which itself is difficult task cos of too many pads.


Sent from my iPhone using Tapatalk
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Old 08-04-2017, 09:01   #3 (permalink)
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Quote:
Originally Posted by seve91 View Post
Hi guys, got this iphone 6 with U1700 desoldered, with some ripped pads that need to be rebuilt.
The missing pads are:
B3 - USB0_DN that goes to 90_AP_BI_TRISTAR_USB0_N
C2 - BRICK_ID that goes to TRISTAR_TO_PMU_USB_BRICKID
D3 - SDA that goes to AP_BI_I2C0_SDA
D4 - SCL that goes to AP_TO_I2C0_SCL
E2 - UART0_TX that goes to AP_TO_TRISTAR_ACC_UART6_TXD (directly under the CPU)
E4 - SWITCH_EN that goes to RESET_1V8_L
Are all these pads necessary? It's quite difficult to rebuild those pads, because there aren't visible routes, they all go under the top layer.
Advices? Thanks
You don't need jumpers, is better to rebuild pads with wire and copper paper foil.
difficult to find the foil with no glue, the one with glue is fine just need to scrape glue off.

Definitely you need a scope and good iron with .02 mm tip or .001 if you have a hakko.

1 - What I do is to scrape off some board to reveal pad connector (use #11 surgery knife)
2- Solder peace of wire long enough to go to the other side (beyond pad edge)
3- make pad out of copper foil
4- tin pad with solder
5- place pad under the wire
6- run wire on top to the edge
7- use UV green board insulator to glue wire to the edge of the pad (so it will not come off when you heat the board or chip)
8- cure with UV light (make sure green protector is not to high) shave it off a bit after cure if necessary.

There you go.
I learn how to do that my self after I pulled 4 pads out of a board and then on a Nand... well couple on my early days and don't feel bad, still happening with crazzy black glue

Good luck,
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Old 08-04-2017, 09:14   #4 (permalink)
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Here is a pic of a Nand I fixed

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Old 08-06-2017, 11:58   #5 (permalink)
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Quote:
Originally Posted by shani1122 View Post
You pulled out too many pads mate, some of them are necessary. So you need to rebuild the pads with jumpers which itself is difficult task cos of too many pads.


Sent from my iPhone using Tapatalk
hi could you tell me the necessary pads? I've successfully restored the pads with visible route, but those pads got routes that go directly under the pads.

Quote:
Originally Posted by cisco2017 View Post
You don't need jumpers, is better to rebuild pads with wire and copper paper foil.
difficult to find the foil with no glue, the one with glue is fine just need to scrape glue off.

Definitely you need a scope and good iron with .02 mm tip or .001 if you have a hakko.

1 - What I do is to scrape off some board to reveal pad connector (use #11 surgery knife)
2- Solder peace of wire long enough to go to the other side (beyond pad edge)
3- make pad out of copper foil
4- tin pad with solder
5- place pad under the wire
6- run wire on top to the edge
7- use UV green board insulator to glue wire to the edge of the pad (so it will not come off when you heat the board or chip)
8- cure with UV light (make sure green protector is not to high) shave it off a bit after cure if necessary.

There you go.
I learn how to do that my self after I pulled 4 pads out of a board and then on a Nand... well couple on my early days and don't feel bad, still happening with crazzy black glue

Good luck,
Hi, thanks for your help...Please explain better, i didn't understand very well your method...i usually scrape around the PAD to find the route, then i solder a wire from the route to the center of the ripped pad.
But those pads doesn't have a visible route around them, the route goes directly under the center of the ripped pad
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Old 08-06-2017, 18:44   #6 (permalink)
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Hi, this is the actual situation:



some pads have been rebuilt, others i scratched the board to find a track (route) where to solder a wire and rebuild the pad.
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Old 08-07-2017, 06:49   #7 (permalink)
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Quote:
Originally Posted by seve91 View Post
Hi, this is the actual situation:



some pads have been rebuilt, others i scratched the board to find a track (route) where to solder a wire and rebuild the pad.
If trace goes under pad then there will be a pin like solder (don't go to deep and be careful you might destroy it)

You need to use a fine point .01 or .02 mm solder to tin that pin like trace with solder (you'll be able to get a pin head amount of solder on it)

solder a wire on that trace

run the wire out and use green UV PCB insulator to glue the end of that wire to the outside of the trace whole (so it won't move)

now you can put a bit more solder on top of that pin head trace (use flux so it flows to it)

If you want to make the pad look and have more surface you can add a copper foil made pad on top and cover with solder (not so easy since it will move very easy)

Sorry my friend, I'm not a guide writing guy so I'm just helping you with what I can.


BTW:
another way to get a pad on top of that under ping is to put a copper pad on top, but you MUST put solder on top of that pin trace so it flows with the top pad. Then use UV mask around the pad to keep it in place.
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Old 08-07-2017, 07:20   #8 (permalink)
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Hope this is in some help for you

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Old 08-07-2017, 20:48   #9 (permalink)
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ok you're now clear...as you can see in the photo i tried to scratch to find the track.
Is there a program that shows the path of the tracks under the top layer?
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Old 08-08-2017, 04:45   #10 (permalink)
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Quote:
Originally Posted by seve91 View Post
ok you're now clear...as you can see in the photo i tried to scratch to find the track.
Is there a program that shows the path of the tracks under the top layer?
try and use a solder tip, flux and a "bit" of solder on the whole you made and check if some of the solder had solder on something. The pin is there.
I was trying to change the color on your pic to see if I can see something there but you have to much flux and it shines.

You can do the same, clean with alcohol and you'll get a better view.
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Old 08-08-2017, 20:32   #11 (permalink)
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it is hard to find the track, is very thin...my soldering iron is an aoyue 2900....could you suggest a new cheap but good soldering iron with thin tips?
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Old 08-09-2017, 07:54   #12 (permalink)
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I my self use an Aoyue 968A will upgrade soon, in need of micro tweezers.

Don't know your budget you can try the Aoyue 9378 60 Watt Programmable Digital Soldering and on that you can change tips.
If too expensive for you then search for that name in Amazon and it will give you more options and different brands, what you are looking for is to be able to change tips and more important to be able to use the more common tips out there Aoyue hakko and then to be able to change temperatures.
Aoyou tips cost around $3+ Hakko tips around 11+
SMD soldering you'll need temperatures from 200 C (leaded solder) to 330 C (lead free solder)
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Old 08-09-2017, 19:11   #13 (permalink)
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in my aoyue 2900 i got a very thin tip (i suppose 0.2mm) but it can't melt the solder, even if i set 480°C.
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Old 08-10-2017, 03:56   #14 (permalink)
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Quote:
Originally Posted by seve91 View Post
in my aoyue 2900 i got a very thin tip (i suppose 0.2mm) but it can't melt the solder, even if i set 480°C.
yea is a bit of a trick to use micro tips.

First you need to buy low melting solder 130 C

mix that with the current solder and wick it out, the low melt will mix and allow you to wick it at low temperature.
You can easily remove lead free solder that melts at 230°C when mixed with 130°C solder.

then use low solder only to work on those pads,

480°C is a lot of heat, but lucky you it is not making it to the board because of the tip.

The micro tips don't have much heat at the tip, you can research that on the net "how solder iron tip works"
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Old 08-15-2017, 09:00   #15 (permalink)
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i used a new method...scratched the "hole" where was the pad, until i find a track or a pin.
Then i put some flux and some solder paste, and i use hot air.
The solder paste will melt and it will attach to the pin or the track.
Then i will check the link using the multimeter (to check if i catched the right track or not), and i will solder a tiny piece of wire to make the pad.
After that, i will use some green pcb mask to cover the solder
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