ruslan.tulupov
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Pi 4 PCB Defect? (fiberglass thread loose)

Mon Jul 15, 2019 2:43 am

Hey everyone,

I recently purchased Pi 4 1GB and 2GB models from Vilros and noticed the 1GB has a part of the PCB barely attached by the GPIO.

Will this affect usability or reliability in any way?
Should I return this board?

Thanks in advance.

Video of the issue (0:50):
https://youtu.be/djrsld8aX8M
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Imperf3kt
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Re: Pi 4 PCB Defect?

Mon Jul 15, 2019 3:20 am

A photo and perhaps description would be better.
In that video, at the 50 second mark, I see no defect.
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Re: Pi 4 PCB Defect?

Mon Jul 15, 2019 3:21 am

The insulating parts of PCBs are made from fiberglass soaked in resin. What it looks like happened to me is that while milling the board to shape a fiber that was right on the edge tore out when the board was milled into shape.

Normally designers keep the actual tracks a fair distance away from the edge, so that any damage from the milling (or worse v-scoring and breaking) process doesn't affect the electronics, so I doubt this will pose any functional issue.

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jbeale
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Re: Pi 4 PCB Defect?

Mon Jul 15, 2019 3:25 am

If you're talking about 0:47 I see along the top edge what may be a sliver of FR4 or whatever PCB board material they are using, I would assume due to a slightly rough cut when they separated that specific board from the larger panel during manufacturing.

When you layout a board you have to follow design rules including "keep back" distances from the edge of the board, to allow for manufacturing tolerances when the board is cut. As a result, this kind of thing should not affect the function or reliability of the board. It might not be nice to the fingers if you hold the board along a sharp rough edge though.

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mahjongg
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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Mon Jul 15, 2019 8:51 am

If you are talking about the thin fiberglass thread that comes loose of the board edge at 01:05 then no, that has no consequence to how the PI will work. You can pull off the thread and throw it away, it has no metal on it.

If you open up any low-cost modern electronics equipment, and look at the PCB's you will see this is a common "problem".

p.s. deleted duplicate of this post.

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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Mon Jul 15, 2019 10:39 am

It´s not an defect. Its from cuting the PCB and I think that most RPI4 Users have this ""Desing Defect"". Even my 2Gb Pi 4 had this (but it wasn´t that big as your ""Defect""). On functionality part: It´s okay and you can use your Pi normally. If you want, you can slowly peal it off. I did that too and my Pi is still working :D . In fact. I typing this reply on my Pi ; 8-)
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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Tue Jul 16, 2019 12:46 am

Thanks for the replies - booted it up today and seems to work fine 8-)
Will update this thread if issues crop up.
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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Tue Jul 16, 2019 12:59 am

From the description of what it actually is, I suspect a light touch with a fine file would clean it up nicely.

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Imperf3kt
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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Tue Jul 16, 2019 1:24 am

W. H. Heydt wrote:
Tue Jul 16, 2019 12:59 am
From the description of what it actually is, I suspect a light touch with a fine file would clean it up nicely.
I second this.
My Pi4b came with a rather rough edge (I stabbed myself with mine)
Just rub it back with something flat to break loose any large burrs and then hit it (gently) with some fine grit wet sandpaper.

You only need a very small shaving removed to clean up the edge.


Use of a mask is advised.
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pi9
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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Tue Jul 16, 2019 2:44 am

I am surprised quality control wouldn't catch something like this. I never saw this in any of the board I buy from China

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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Tue Jul 16, 2019 6:06 am

I'll let the HW guys know. Whilst not a problem functionally, it's probably something that can be sorted.
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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Tue Jul 16, 2019 9:33 am

Imperf3kt wrote:
Tue Jul 16, 2019 1:24 am
W. H. Heydt wrote:
Tue Jul 16, 2019 12:59 am
From the description of what it actually is, I suspect a light touch with a fine file would clean it up nicely.
I second this.
...
Use of a mask is advised.
The dust from the resin probably won't be a problem, but glass fibre dust isn't nice - it can get deep into the lungs and cause problems.
Maybe try some Selotape or similar to pull the fibre off.

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mahjongg
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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Wed Jul 17, 2019 1:35 pm

pi9 wrote:
Tue Jul 16, 2019 2:44 am
I am surprised quality control wouldn't catch something like this. I never saw this in any of the board I buy from China
Nonsense, its a common occurrence if you make multiple rectangular PCB's in an array from a large plate, and then separate the PCB's from each other with a V-cut (groove).

The board from China you saw were probably one-off's, non rectangular edge milled. Not mass produced rectangular boards.

most often the V-cut cleanly separates the boards, but as glass fiber boards are made from fiber, (duh) sometimes if the cut is happening along the fiber thread, as it would. then single threads might break off along the break edge.

Its purely an aesthetic issue, and the product is too low cost to manually clean the edges of the boards, so quality control ignores this as a non-issue.

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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Thu Jul 18, 2019 3:41 am

I print and cut my own boards and little tags like this happen every once in a while and don't impact the function or lifespan of the product. The previously mentioned file method works, or even just take a pair of small side snips and carefully lop it off.

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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Thu Jul 18, 2019 4:51 am

M_P wrote:
Thu Jul 18, 2019 3:41 am
I print and cut my own boards and little tags like this happen every once in a while and don't impact the function or lifespan of the product. The previously mentioned file method works, or even just take a pair of small side snips and carefully lop it off.
Oh... Is that what people are calling diagonal cutters these days? (I'd probably get some grief form the moderators if I gave the traditional name.)

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Re: Pi 4 PCB Defect? (fiberglass thread loose)

Thu Jul 18, 2019 9:46 am

Or you could use a simple potato peeler knife, and rub it along the edge of the PCB. :mrgreen: This isn't rocket science.

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