Newbie advice needed for identifying and testing SMD capacitors

[sky_shrimp]

Hi all,

I'm very new to electronics and would like to try repairing some iPhone logic boards. By new, I mean I've only turned a multi-meter on once and made something bleep with a continuity test!

I've found a missing capacitor on a board I'm attempting to fix. The schematic for the iPhone 5c states that the capacitor is,

0.1UF 10% 6.3v CERM-X5R 0201

When I google this, I can't find anything to do with CERM-X5R, just X5R. Are they two different capacitors?

 

[Mikebits]

Hi all,

I'm very new to electronics and would like to try repairing some iPhone logic boards. By new, I mean I've only turned a multi-meter on once and made something bleep with a continuity test!

I've found a missing capacitor on a board I'm attempting to fix. The schematic for the iPhone 5c states that the capacitor is,

0.1UF 10% 6.3v CERM-X5R 0201

When I google this, I can't find anything to do with CERM-X5R, just X5R. Are they two different capacitors?

The cerm just means ceramic capacitor. Now for the missing cap. There are many times when a designer places a pad for a part but it is not installed at the factory for whatever reason, so that is most likely the reason it is not installed, and by you installing it, you will just make things worse.
So let me get this straight, you have no formal electronics training and somehow you thought you could just start fixing complicated smart phones. Hmm

 

[granddad]

Where to start...

 

[Mickster]

I am certainly not going to try and discourage you from making an attempt at this, but be very aware of the fact that with an admitted lack of experience with electronics and test equipment, the chances of success are going to be extremely low, especially with packages of this size and the equipment needed to service them.
For an idea of the type of equipment you are going need, have a look at Louis Rossmann's youtube page.
He has been doing Apple laptop repairs for years and loathes to touch iphones.
Just a head's up.

 

[large_ghostman]

Hi all,

I'm very new to electronics and would like to try repairing some iPhone logic boards. By new, I mean I've only turned a multi-meter on once and made something bleep with a continuity test!

I've found a missing capacitor on a board I'm attempting to fix. The schematic for the iPhone 5c states that the capacitor is,

0.1UF 10% 6.3v CERM-X5R 0201

When I google this, I can't find anything to do with CERM-X5R, just X5R. Are they two different capacitors?

Hi, can I ask why you think the gap shouldnt be there? There are many boards designed to have different configurations and its normal to find complex boards and schematics that dont fit, you need to be 100% sure the cap is supposed to be fitted on the BOARD you HAVE. triple check its actually meant to be there first then come back, 10 out of 10 for ambition though

 

[audioguru]

Didn't the circuit work perfectly without the missing capacitor then it failed? Then the missing capacitor has nothing to do with the problem.

 

[sky_shrimp]

The cerm just means ceramic capacitor. Now for the missing cap. There are many times when a designer places a pad for a part but it is not installed at the factory for whatever reason, so that is most likely the reason it is not installed, and by you installing it, you will just make things worse.

Thanks. I assumed it meant ceramic but wanted to be sure as I don't want to order the wrong capacitor. I've got other 5c logic boards so I know that capacitor is meant to be there.

So let me get this straight, you have no formal electronics training and somehow you thought you could just start fixing complicated smart phones. Hmm

Pretty much yes, but don't worry. These phones are mine. I'm not trying to repair other people's property.

I am certainly not going to try and discourage you from making an attempt at this, but be very aware of the fact that with an admitted lack of experience with electronics and test equipment, the chances of success are going to be extremely low, especially with packages of this size and the equipment needed to service them.
For an idea of the type of equipment you are going need, have a look at Louis Rossmann's youtube page.
He has been doing Apple laptop repairs for years and loathes to touch iphones.
Just a head's up.

Thanks,

It was the various YouTube videos regarding iPhone repairs that got me to try this. I've bought a rework station, a 200x USB microscope and a few faulty phones to get me started.

Didn't the circuit work perfectly without the missing capacitor then it failed? Then the missing capacitor has nothing to do with the problem.

The phone didn't respond to touch. After inspecting the logic board, I found two blobs of solder causing shorts,

I found out the capacitor was missing after removing the first blob with an iron,

I was planning on making a thread, showing what I'm getting up to in the right section. I just have a few questions that I thought belonged here first.

 

[sky_shrimp]

Hi, can I ask why you think the gap shouldnt be there? There are many boards designed to have different configurations and its normal to find complex boards and schematics that dont fit, you need to be 100% sure the cap is supposed to be fitted on the BOARD you HAVE. triple check its actually meant to be there first then come back, 10 out of 10 for ambition though

This is C137 on another 5c logic board just to confirm,

 

[large_ghostman]

I would use any ceramic smd cap around 0.1uf, they have specified 10% so it cant be too critical. Well dont having a go at this , you might not repair it by trying but you sure as hell wont fix it if you dont try!

 

[Mickster]

The last pic in post #7 shows that the pads have been torn from the PCB.
The first pic looks like a cap was there, as you can clearly still see the pads.
Removing the blob with too large a tip, too much heat, being rough or spending too long to do it is likely the cause IMHO, or a combination.
Unless you are showing 2 different PCB's?

 

[sky_shrimp]

Hi, no it's the same PCB in both pics. There was no cap there after I removed the blob with 1mm solder braid.

It was my first time using a solder iron so I must have done this damage if you can clearly see the pads in the first pic. I thought this damage was done by whoever placed that blob over it.

 

[Mickster]

The blobs most likely came to land where they did when the shields were removed.

 

[sky_shrimp]

This phone came to me without EMI shields.

I assumed whoever touched this last, removed C137 and tried to put a blob of solder on that area, in an attempt to make a quick and dirty jumper, but ended up shortening it instead. The antenna was missing in the phone and the WIFI cable was snapped, which suggests the logic board was pulled out of the case by force.

There was no cap under the blob of solder. I would have seen it on the solder braid but I may be wrong of course. I used the iron at 398c and only pressed on the solder braid with the iron on top every 7 to 10 seconds.

That was obviously too long if I melted the pads you can see in the first pic. The melted TermoPasty flux obscured my vision in that area as I was working. I had to clean the area after each attempt with isopropanol.

What puzzles me about the image with no pads is what looks like a metal strip connecting both traces where the pads should be. It looks to be under some kind of resin. Maybe that's what the PCB looks like underneath.

I've ordered a bare 5c logic board to dissect/file down so I can see what should actually be where underneath that area.

 

[Mickster]

Without doubt that PCB will be multi-layer, meaning there will be more traces inside the PCB besides what you see on the top and bottom.
You are likely seeing one of the traces on the next layer down, how many layers there actually are, I do not know.

If the source of these logic boards to you, is originally from e-waste, they are not going to care about breaking things when separating PCB's, batteries, metal, glass etc.

 

[sky_shrimp]

Hi, I bought this iPhone from eBay. The seller claimed they also bought it from eBay thinking it was working.

The last pic in post #7 shows that the pads have been torn from the PCB.
The first pic looks like a cap was there, as you can clearly still see the pads.
Removing the blob with too large a tip, too much heat, being rough or spending too long to do it is likely the cause IMHO, or a combination.
Unless you are showing 2 different PCB's?

Hi, I knew iPhone logic boards are multi-layered, but what I discovered under the solder blob is actually 'above' the surface of the board though.

The last pic of the cleaned area might be giving the illusion that I burned a crater, but it's embossed.

I practiced removing a SMD capacitor on a spare PCB and did so without damaging the pads. I used more heat than I did on the logic board too.

I lightly scratched the surface of the werid embossed area and found it was copper. I was thinking that the pads are still there but someone has attempted to make a jumper across them from an previous repair.

I'm waiting for the 5c bare board to arrive from China so I can dissect this area.

What are your thoughts on this?

 

[debe]

Personaly I have repaired a couple of I pads where sockets have been torn off. But a Phone is getting a bit small, but I say to you Keep going as you will get better at small soldering with practice & this will be a very good skill to have.

 

[Mickster]

Is the last image the same board as in post#7?
It looks, to me, like you have exposed copper from the layer below during the 'scratching' and folded a sliver over the top of the ground side of C137.
There are no pads left there, only a small piece of the left side of C137 pad, which now has copper from the next layer curled up at the edge.

 

[sky_shrimp]

Yep, definitely the same board. There are scratches on the IC next to C137 that identify it.

The thing about this exposed copper is, it's literally all above the board. It's impossible for it to be from the layer below due to this. The light scratch you see is one clean scratch. There's no sliver folding over. Thanks for the replies though. I'll start a thread about this when I get the bare 5c board from China which should be arriving soon. I need to cut into the C137 area to see what's underneath.

I now have a MS8910 smart SMD tweezer and already see I need a more advanced one.

I need to order some ceramic caps to replace the many components I've found missing from the schematic. As previously mentioned, some may not be present on the production board. Either way I'm having a lot of fun with this I'm glad I found this forum and really appreciate your replies. There's so much to learn and I'm really eager to get up to speed.

I'll share my repair pics and updates on the new thread for anyone interested.

First I'll have to order some new caps. I'll list the ones I need and hopefully someone can chime in on what I need to google. I really don't want to order the wrong ones and screw up the repairs.

 

[Mickster]

I have put your pics side by side for comparison. The right is the one before you started poking around and the left is the latest you provided.
The copper you are seeing in the crater created by you, is from another layer within the PCB.
How much you have been poking and removing PCB substrate can be seen from the red, blue and the green arrows I added to your image on the left.
The green arrow shows how much you have elongated the crater, the red arrows show how you have deepened the crater and the blue arrows show copper, which was not there on the original image, folded up from a lower layer and laid across the top of the PCB.

I don't think anyone else is likely to disagree with what I have shown.

Regards.

 

[sky_shrimp]

Thanks Mickster,


You are 100% correct! I'm glad I shared those pics. I was so convinced I was seeing an embossed area but it was indeed a crater. I honestly thought I was just lightly scratching and exposing a welded lump of copper that was placed above the board by a previous repair.

This is the illusion I was seeing. Copper already connecting the two traces over the board

I was viewing it with a perfect ring of LEDs around the microscope lens. After switching off the LEDs and viewing it with a light on either side, I saw exactly what you're seeing.

I also see the sliver you mentioned now casting shadow.

I was advised to remake the pads with copper wire like this,

I was really confused by this solution at first because it looked like both traces were already connected under my imaginary lump of copper o_0

I'll fill the hole and make new pads. Then I intend to connect the pads to the traces with fine copper wire.

Trouble is, I've made a bit of a pigs ear out of the left trace as you can see. It was one silver looking trace before I started scratching lightly. It looks like 3 traces now, with one sliver pointing upwards.