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mahjongg
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Re: What size screw driver for Philips and bolts do I need?

Thu May 06, 2021 3:24 pm

drgeoff wrote:
Mon May 03, 2021 7:14 pm
mahjongg wrote:
Mon May 03, 2021 11:29 am
I see no evidence of snap off points or V-cuts on the RPI's I have
See https://www.raspberrypi.org/blog/sony-t ... ete-lomas/ for the evidence that has been removed at some point prior to shipping.
yes, It was exactly as I was expecting, the sides where no stresses while breaking apart are simply routed out, and the other two sides use v-cuts.
where there are connectors that stick out, a small strip is inserted in between the v-cut sides.
Care must be taken to break out the panel into loose boards, so that there are no stresses on the PCB traces or SMT parts while breaking the v-cuts.
Especially larger ceramic capacitors could break if placed to close to a v-cut.

Also with this methods (routed edges and v-cuts) there really are no "break points", which are rows of very tiny holes at the break off points to weaken the point where the PCB's are broken off from each other. such break off points (with rows of tiny holes) are often used with cheaper PCB panels.

Below is a picture showing "break off points", and how to make sure the strips can be broken of by adding strategically placed extra break off points, on the edges of the strips. But as I said, Sony does NOT use this technique for raspberry PI's.

Image

jamesh
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Re: What size screw driver for Philips and bolts do I need?

Thu May 06, 2021 3:52 pm

Imperf3kt wrote:
Tue Apr 27, 2021 9:56 pm
Not to mention the Pi's are not manufactured one at a time, but in a large pcb sheet and snapped off from each other.
Indeed, but the test machines takes them in one at a time once they are fully completed. Think the holes are used for location at that point. They are the size they are because we cannot make them any larger and still fit everything else on the board!
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 7:53 am

jamesh wrote:
Thu May 06, 2021 3:52 pm
They are the size they are because we cannot make them any larger and still fit everything else on the board!
I'm having trouble reconciling that with reports of people opening up the holes to use M3 bolts and their boards still work. :)
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 9:24 am

drgeoff wrote:
Fri May 07, 2021 7:53 am

I'm having trouble reconciling that with reports of people opening up the holes to use M3 bolts and their boards still work. :)
I've used M3 stand-offs on several of my pi project with out any problems , I just used a rat tail file to open the holes on the pi ,

they only require enlarging a very small amount and if you hold a pi up to the light you can see there are no tracks or ground plane close to the

holes, in the light coloured area around the hole.

If the holes are in fact 2.8mm then you are only increasing the size by 0.2mm which is still well within the light coloured area on the PCB
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 9:29 am

drgeoff wrote:
Fri May 07, 2021 7:53 am
jamesh wrote:
Thu May 06, 2021 3:52 pm
They are the size they are because we cannot make them any larger and still fit everything else on the board!
I'm having trouble reconciling that with reports of people opening up the holes to use M3 bolts and their boards still work. :)
Bigger holes = larger areas around the holes that cannot have anything in them. Drilling out the hole doesn't make the area any larger, but it should be to meet the EMC specs.
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 9:34 am

jamesh wrote:
Fri May 07, 2021 9:29 am
drgeoff wrote:
Fri May 07, 2021 7:53 am
jamesh wrote:
Thu May 06, 2021 3:52 pm
They are the size they are because we cannot make them any larger and still fit everything else on the board!
I'm having trouble reconciling that with reports of people opening up the holes to use M3 bolts and their boards still work. :)
Bigger holes = larger areas around the holes that cannot have anything in them. Drilling out the hole doesn't make the area any larger, but it should be to meet the EMC specs.
Anyone else understand that?
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LTolledo
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 9:53 am

I did enlarged the mounting hole of one of my RPi to ⌀3.5mm so I can use M3 resin standoffs

checking my RPi4B-4GB the non-masked portion on the mounting holes has a diameter of 5.5mm (correction please)

looking at some bolt and screw tables,
1. M2.5 pan screws have a maximum head diameter 5mm, M3 pan screws have 6.0mm (based on DIN7985)
2. M2.5 allen cap's head diameter is at 4.5mm... a M3 allen cap have 5.5mm
3. M2.0 truss screws have a head diameter of 4.5mm, M2.5 truss have 5.7mm
4. M2.5 brass standoff (that I have) has max diameter 5.1mm, M3 ones have 6.2mm

so I think the holes were originally designed to be safely used with M2.5 pan screws, allen cap crews, and metallic standoffs....or M2 truss screws.... ;)
Last edited by LTolledo on Fri May 07, 2021 12:59 pm, edited 1 time in total.
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 10:50 am

drgeoff wrote:
Fri May 07, 2021 9:34 am
jamesh wrote:
Fri May 07, 2021 9:29 am
drgeoff wrote:
Fri May 07, 2021 7:53 am

I'm having trouble reconciling that with reports of people opening up the holes to use M3 bolts and their boards still work. :)
Bigger holes = larger areas around the holes that cannot have anything in them. Drilling out the hole doesn't make the area any larger, but it should be to meet the EMC specs.
Anyone else understand that?
Yes (though I had to read it twice).
Put it the other way round:
  1. EMC specs require a track-free area around mounting holes.
  2. The area should be bigger if the holes are bigger.
  3. The area does not grow without a (very) difficult board redesign.
  4. If the existing holes are drilled, the EMC spec will be violated.
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jamesh
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 1:54 pm

davidcoton wrote:
Fri May 07, 2021 10:50 am
drgeoff wrote:
Fri May 07, 2021 9:34 am
jamesh wrote:
Fri May 07, 2021 9:29 am


Bigger holes = larger areas around the holes that cannot have anything in them. Drilling out the hole doesn't make the area any larger, but it should be to meet the EMC specs.
Anyone else understand that?
Yes (though I had to read it twice).
Put it the other way round:
  1. EMC specs require a track-free area around mounting holes.
  2. The area should be bigger if the holes are bigger.
  3. The area does not grow without a (very) difficult board redesign.
  4. If the existing holes are drilled, the EMC spec will be violated.
Yeah, that....

(although I have never seen any issues with drilling the holes out)
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Working in the Application's Team.

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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 3:55 pm

davidcoton wrote:
Fri May 07, 2021 10:50 am
  1. EMC specs require a track-free area around mounting holes.
  2. The area should be bigger if the holes are bigger.
  3. The area does not grow without a (very) difficult board redesign.
  4. If the existing holes are drilled, the EMC spec will be violated.
@davidcoton
Are you agreeing that with that or just stating you interpretation of what jamesh wrote.
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 4:08 pm

drgeoff wrote:
Fri May 07, 2021 3:55 pm
davidcoton wrote:
Fri May 07, 2021 10:50 am
  1. EMC specs require a track-free area around mounting holes.
  2. The area should be bigger if the holes are bigger.
  3. The area does not grow without a (very) difficult board redesign.
  4. If the existing holes are drilled, the EMC spec will be violated.
@davidcoton
Are you agreeing that with that or just stating you interpretation of what jamesh wrote.
I am just rewording jamesh's post, in response to your post implying that you did not understand it. I have no detailed knowledge of EMC practice or relevant specs.

My personal take on it all is that drilling out is not recommended, and is done at your own risk, but does not usually cause actual problems.
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drgeoff
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 5:00 pm

davidcoton wrote:
Fri May 07, 2021 4:08 pm
drgeoff wrote:
Fri May 07, 2021 3:55 pm
davidcoton wrote:
Fri May 07, 2021 10:50 am
  1. EMC specs require a track-free area around mounting holes.
  2. The area should be bigger if the holes are bigger.
  3. The area does not grow without a (very) difficult board redesign.
  4. If the existing holes are drilled, the EMC spec will be violated.
@davidcoton
Are you agreeing that with that or just stating you interpretation of what jamesh wrote.
I am just rewording jamesh's post, in response to your post implying that you did not understand it. I have no detailed knowledge of EMC practice or relevant specs.

My personal take on it all is that drilling out is not recommended, and is done at your own risk, but does not usually cause actual problems.
OK. I'm sceptical that EMC specs would themselves stipulate a minimum track free area around mounting holes. But I haven't read EMC specs so my scepticism may not be justified.

Nor would I immediately accept that for a RPi board to satisfy EMC emission and tolerance levels a minimum track free area around mounting holes was a contributing factor.

Any certified EMC engineer able to convince me one way or the other?
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gordon77
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Re: What size screw driver for Philips and bolts do I need?

Fri May 07, 2021 7:12 pm

In this document https://www.emcstandards.co.uk/files/pc ... 1999_1.pdf it talks about keeping any holes, including mounting, away from noisy, dirty, high speed or especially sensitive EM zones.

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