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Dear all,
I have spent some time disassembling my Nexus 5 and I found that the shielding cover that faces the die-casting has a strange "gold" tape on it (cf. picture enclosed).
I am curious, does anyone know what is it ? Is it a "high" thermal conductivity material that send the heat to the die-casting ? Or is is electrically non-conductive material that avoid leakage ?
I am a bit concerned because if it is for heat transfer, why not putting something on the CPU too ?
Thx for your feedbacks.
fredo490 said:
Dear all,
I have spent some time disassembling my Nexus 5 and I found that the shielding cover that faces the die-casting has a strange "gold" tape on it (cf. picture enclosed).
I am curious, does anyone know what is it ? Is it a "high" thermal conductivity material that send the heat to the die-casting ? Or is is electrically non-conductive material that avoid leakage ?
I am a bit concerned because if it is for heat transfer, why not putting something on the CPU too ?
Thx for your feedbacks.
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Click to collapse
In the service manual it descripted as "Can Assembly,Shield" and the clips of it named as "SMT Boss / Screw / Shield can frame"
The best person to ask would be @AdamOutler. Can you give any insight?
Woven copper tape is both thermally and electrically conductive. Its been a while since I looked inside mine, so I don't really remember it.
Those schematics are funny though.. Ground connected to pin 1... 25 times
AdamOutler said:
Woven copper tape is both thermally and electrically conductive. Its been a while since I looked inside mine, so I don't really remember it.
Those schematics are funny though.. Ground connected to pin 1... 25 times
Click to expand...
Click to collapse
Thanks!
AdamOutler said:
Woven copper tape is both thermally and electrically conductive. Its been a while since I looked inside mine, so I don't really remember it.
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Click to collapse
So it is a copper tape, thanks for the info. But why is the color so "yellow"? It doesn't actually look like copper.
There is still a thing that I don't understand: the hot spot should be the CPU, why not contacting it to the die casting instead of the shielding cover ?! To me, there is something that doesn't really make sense in this design.
Edit: interesting enough, it seems that the LG G3 uses the same concept (cf. enclosed). Die casting in the middle with this "gold" tape on the shielding cover. It seems to be a reference design for LG.
AdamOutler said:
Woven copper tape is both thermally and electrically conductive. Its been a while since I looked inside mine, so I don't really remember it.
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Click to collapse
We use this stuff at work for RF gaskets for EMC. Here's an example: LeaderTech SF030PCU-CA
My guess is that it's to complete the EMI shield around the cutouts for the SoC and the couple of other parts poking through. Look at the mill-out where the PCB sits on the chassis for the SoC. By doing this, they can shave off a mm or two on the phone.
Those schematics are funny though.. Ground connected to pin 1... 25 times
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Click to collapse
Those are all the ground points on the board that aren't part of components. Like screw holes, friction ground contacts, and the shield can. Standard stuff to throw odds and ends that don't make sense elsewhere in the schematic on a single page. On some of the stuff I work on, with hundreds of 11x17 pages for a single board, it's not uncommon to have pages dedicated to holes, bypass caps, and mechanical stuff, all with no regard to pin numbers.
fredo490 said:
So it is a copper tape, thanks for the info. But why is the color so "yellow"? It doesn't actually look like copper.
Click to expand...
Click to collapse
Probably some sort of alloy, nickel/copper. See the link above. Pure copper would corrode too easily.
There is still a thing that I don't understand: the hot spot should be the CPU, why not contacting it to the die casting instead of the shielding cover ?! To me, there is something that doesn't really make sense in this design..
Click to expand...
Click to collapse
Ah, a common misconception about chip packaging.
High power chips like PC CPUs need a lot of heat pulled away from them quickly, and the most efficient way is by facing the back of the die away from the package PCB so a heatsink can be slapped on top. These always are left open-top or have a heat spreader of some sort.
But for most chips, the back of the die is bonded to the package PCB (or leadframe) and bond wires used to jumper the die to the package. For chips that need to be cooled, there are dozens or hundreds of vias in the package PCB (metal plated holes through the PCB) and BGA pads on the other sides of the vias. These are called thermals, and conduct heat from the chip die to pads on the BGA. If you look at the back of a typical BGA, these show up as a separated square array of pads in the middle.
The designer of the PCB that uses this chip will design in thermals between the BGA thermal pads and the ground layer(s). The ground layers are nearly solid sheets of copper, and the thermal vias let it act as a heat spreader.
Also, the SoC in the N5 is a multi-chip package (MCP) and has a second BGA with the DRAM sitting on top of the Snapdragon BGA. The Snapdragon BGA PCB has solder balls on top that make contact with the DRAM BGA. It's all covered in rich creamy epoxy, which isn't all that good at conducting heat.
All this leads up to the top of the Snapdragon 800 package being the least useful place to try pulling away heat.
pokey9000 said:
Those are all the ground points on the board that aren't part of components. Like screw holes, friction ground contacts, and the shield can. Standard stuff to throw odds and ends that don't make sense elsewhere in the schematic on a single page. On some of the stuff I work on, with hundreds of 11x17 pages for a single board, it's not uncommon to have pages dedicated to holes, bypass caps, and mechanical stuff, all with no regard to pin numbers.
Click to expand...
Click to collapse
Believe me, I've worked with plenty of schematics before. I just find it funny that they would label chasis ground as pin 1. Generally that's just ground. Someone obviously had too much time on their hands, considering its an EM shield being called pin 1.
AdamOutler said:
Believe me, I've worked with plenty of schematics before. I just find it funny that they would label chasis ground as pin 1. Generally that's just ground. Someone obviously had too much time on their hands, considering its an EM shield being called pin 1.
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Click to collapse
I think it depends on the EDA tool and the whim of the library maintainer. From the little symbol creation I've done in KiCAD I think pin number visibility can be turned off for a symbol. I'm looking right now at one of our designs, and half the page is plated drill holes, each numbered pin 1. What's better, on the same page is a single high current screw terminal with 4 leads holding it to the board. It's one solid piece of metal, but the symbol shows pins 1-4.
fredo490 said:
Dear all,
I have spent some time disassembling my Nexus 5 and I found that the shielding cover that faces the die-casting has a strange "gold" tape on it (cf. picture enclosed).
I am curious, does anyone know what is it ? Is it a "high" thermal conductivity material that send the heat to the die-casting ? Or is is electrically non-conductive material that avoid leakage ?
I am a bit concerned because if it is for heat transfer, why not putting something on the CPU too ?
Thx for your feedbacks.
Click to expand...
Click to collapse
Going slightly off topic, but could you say if there's something such as a warranty sticker when you open your Nexus to tell that it has been opened?
Thanks in advanced.
ImSoBored said:
Going slightly off topic, but could you say if there's something such as a warranty sticker when you open your Nexus to tell that it has been opened?
Thanks in advanced.
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Click to collapse
I didn't find any warranty sticker in mine. However, it is quite obvious to find if the device has been opened because of the tape holding the back cover. It is almost impossible to open and close it without "damaging" the tape.
fredo490 said:
I didn't find any warranty sticker in mine. However, it is quite obvious to find if the device has been opened because of the tape holding the back cover. It is almost impossible to open and close it without "damaging" the tape.
Click to expand...
Click to collapse
Oh, guess I'll have to wait till my warranty is gone. Still more than one year to go... Thanks btw
After disassembling my phone to change the usb port, camera is not able to focus on nearby objects. I have installed another program to handle the focus manually but not luck, the focus is moving when i slide the bar, but with nearby objects is blurry. Any idea???
Did you replace the port pcb with the same part number?
Check any connectors you took off for damage to the pins or misalignment. Check ribbon cables for damage. Reassemble exactly as it was disassembled... watch some tear down vids, maybe you missed something.
Loose components and pcbs are more susceptible to ESD damage... ESD protocols should be observed. At least keep room humidity above 45%! Wear cotton clothes.
Did you replace the port pcb with the same part number?
It's identical but with different part number.
I cheked the connectors, good solder and alignment. May be i have to use a magnifien lens to check SMD connectors, sometimes when you remove a connector welding can break .......
FalloSistema said:
Did you replace the port pcb with the same part number?
It's identical but with different part number.
I cheked the connectors, good solder and alignment. May be i have to use a magnifien lens to check SMD connectors, sometimes when you remove a connector welding can break .......
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Not identical, wrong part. This could be the cause. To verify this put the old pcb back in to see if it resolves the issue.
If so you need that exact OEM part.
Also the BGA chipsets are impossible to inspect with their dozens of solder joints under the chipset... but I don't think that's the issue.
Finally resolve, the problem is the lens protector, when i removed it, camera focus its very fast even macro scenes.
There are two issues with the lens protector, is lightly gladed, but the most important, the distance between the camera and the lens, as show this video:
Hello! I have a Samsung A32 5G and it won't turn on unless I apply pressure on the ribbon cable. How can I find out if the cable or the connector on the motherboard not working.
Use a pencil eraser to gently poke different spots to try to provoke a response to help isolate the area. Use a good light source and magnification to try and spot solder fractures on the mobo.
If it suffered drops with no case it maybe a mobo failure. The BGA chipsets are intolerant to board flexing and high G loading... a good case makes impacts survivable by reducing both.
New batteries for the XDA Exec/JasJar are not available anymore, so I want to try to equip my old battery with new cells.
I found a suitably thin pair of 3.7v Lipo batteries as a replacement.
I managed to open the old battery and remove the old cells without incident.
The question is now: should I remove the old battery management sysmte I found inside or use the new cells with their own BMS?
The old battery has four contacts, positive, negative, one thermistor and a status indicator.
The new cells I have only have two contacts, positive and negative.
Will the phone work with the middle contacts not being connected? If I remove the BMS of the new cells and connect them to the old BMS, the cells are a different capacity. Would that matter?
You want the thermistor to monitor battery temperature. The power controller may puke all over you without that input and go into default mode. Whatever that is.
Charge state is voltage based so if the cell voltage ratings are the same as the OEM ones it should work. If you solder to the cells you better be quick and proficient at soldering with a temp controlled iron 45-85 watts (I go for 650-720F) and 63/37 flux core solder. Pre-tin any wires...
I soldered the new cells to the old BMS and it's working fine.
The soldering wasn't quick though. The solder was very reluctant to sticking to the metal strips, despite me roughing them up with sand paper and using extra flux. Any suggestions of how to make solder stick more readily?
Is the cell potentially unsafe now? Is there a much higher risk that it will spontaneasly burst into flames?
You should pre tin it. I will aggressively rub the tinned iron tip* on the surface with lots of rosin flux to get it to tin. OK to use excess solder and allow it to drip off as it carries away the contaminants. Allow to cool. On problem surfaces I'll waste a lot of solder just to get them to tin. Got to go with the flow... did production soldering for decades
Once both surfaces are pre tinned then solder. 37/63 solder works best; lower melting point, flows better.
You're probably ok as long as there's no noticable or battery bulging. Maybe do a test cycle or two with the cover loose to test it and make sure the thermistor is still reasonably accurate.
*greatly reduces tip lifespan. Normally you avoid do this. I reccomend using at least a 65 watt iron to overcome the battery's heat sinking capacity. Lower btu's mean unwanted excessive heating of the battery due to excessive heating time. Sometimes bumping up the iron temperature yields a faster solder joint but speed is of essence. Loitering with the heat more then a few seconds is to be avoided. Using the right size/shape tip can increase the heat transfer and help to minimize contact time. Sanding is normally never used to clean solder surfaces in electronics. It may make it harder. Make sure the surface doesn't have a conformal coating, if so remove it first. Brillo pad to clean tips of burnt build up; they don't cut into the tip plating on the tinned zone (destroying them).
I use tips that have a large tinned zone as smaller zones (measured from tip back) will foul much quicker as the burst rosin accumulates no matter how often you wet sponge it and well you keep them tinned.
Get as much tip surface area on the zone to be solder as possible at the get. Soldering is a skill/art that requires practice to learn.
Even aluminum solders easily. Except aluminum oxide doesn't.
Apply oil, sandpaper it, solder through the oil.
Renate said:
Even aluminum solders easily. Except aluminum oxide doesn't.
Apply oil, sandpaper it, solder through the oil.
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Interesting. Cool trick if it works.
Never had to play with that much. Cheap steel lead electronic components are a pain.
Apparently using a very high tin content solder helps, but any zinc chloride if used must be completely removed. Check its melting point first...
Also immediately after soldering quench the battery with a damp cloth to cool it more rapidly.
Any kind of oil? Sunflower oil?
naujoks said:
Any kind of oil? Sunflower oil?
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Lol, I just did a check of my assertion.
I used spray canola oil from the dollar store.
Renate said:
Lol, I just did a check of my assertion.
I used spray canola oil from the dollar store.
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Rosin flux is the O2 sheild when soldering... and it won't permeate into the display. Just use liquid or paste rosin flux and Emery cloth, etc.