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Pcb spacers and holders, absolutely neccesary?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Pcb spacers and holders, absolutely neccesary?
djthopa
Hi my friends,

I have been working on a project that has two pcb’s.

I did all the routing inside eagle but forgot to add the 3mm holes for the spacers that separate the two pcbs.

There are 14 pins going from one pcb to the other.

Power cable is on the outside pcb,

Im concerned about pulling the pcbs apart since they are not phisically attached apart from the pins.

Do you use any other solution? How do you call this plastic hinge in English?



Thanks!
Whelm
We call those zip ties or cable ties.

I haven't really bothered with spacers on modules I've built and haven't had any issues yet. But my synth stays perched on my desk and rarely gets rattled. It's probably not best practices but I haven't encountered trouble.
sduck
What I've done in similar situations is cut some spacers to size out of nylon pieces - usually repurposed spacers, just stick them between the pcbs and then throw a zip tie(s) around them. Works fine, and easy to take apart if you need to rework things later.

Sort of like this -

Random Looping Sequencer back by Stephen Drake, on Flickr
djthopa
Ah ok!

So im not the only one running into this problems!

zip ties! thanks for the info, sometimes I struggle finding the right word.

Great idea about the nylon washers, maybe hold them with some how glue to the pcb? It would get quite messy hmmm.....

Thanks!
Morphology
I have designed several boards that have two sets of 8-pin headers linking the boards together.

Once the module is built, if it's all working as expected, then a small dab of superglue on each header ensures they won't accidentally pull apart.

Morph
Synth Con Meo
Morphology wrote:
I have designed several boards that have two sets of 8-pin headers linking the boards together.

Once the module is built, if it's all working as expected, then a small dab of superglue on each header ensures they won't accidentally pull apart.

Morph


Some of the Kit's I've built from a certain vendor actually suggests doing this too. The other thought would be to use hot glue (sparingly and carefully) so it might be easier to take apart if need be. Just a thought.

Me personally I kind of like the extra security of what the standoffs can provide.
sduck
djthopa wrote:

Great idea about the nylon washers, maybe hold them with some how glue to the pcb? It would get quite messy hmmm.....


Just look at your situation, think a bit, get creative, you'll think of something. Yes, you can glue one end of it. In the one I posted, I wasn't using the the onboard pots or jacks, so there were a bunch of unused holes - I used nylon standoffs that had one threaded end, attached to the bracket, and just cut them to size, with a small part sticking out, and aligned the standoffs with the available holes.

Sometimes there's enough room on the pcb to drill new holes. But check for traces and such!

My TTSH has several add-on PCBs that were attached with nylon standoffs - rather than tempt fate with drilling new holes I just glued them on.
djthopa
Synth Con Meo wrote:
Morphology wrote:
I have designed several boards that have two sets of 8-pin headers linking the boards together.

Once the module is built, if it's all working as expected, then a small dab of superglue on each header ensures they won't accidentally pull apart.

Morph


Some of the Kit's I've built from a certain vendor actually suggests doing this too. The other thought would be to use hot glue (sparingly and carefully) so it might be easier to take apart if need be. Just a thought.

Me personally I kind of like the extra security of what the standoffs can provide.


I have had such bad experiences with super-glue and desoldering that now i only use the glue gun, its messy but easier to remove if needed, thanks for your counsel!
djthopa
sduck wrote:
djthopa wrote:

Great idea about the nylon washers, maybe hold them with some how glue to the pcb? It would get quite messy hmmm.....


Just look at your situation, think a bit, get creative, you'll think of something. Yes, you can glue one end of it. In the one I posted, I wasn't using the the onboard pots or jacks, so there were a bunch of unused holes - I used nylon standoffs that had one threaded end, attached to the bracket, and just cut them to size, with a small part sticking out, and aligned the standoffs with the available holes.

Sometimes there's enough room on the pcb to drill new holes. But check for traces and such!

My TTSH has several add-on PCBs that were attached with nylon standoffs - rather than tempt fate with drilling new holes I just glued them on.


Thanks for the tip, i have some nylon spacers that i can trim and glue once everything is working good ! Not much space for drilling on this one.
fuzzbass
The classic example of where this goes wrong was in a post here, where someone wanted to repair a device whose sub-board was entirely supported by a header that was surface mounted. This was a commercial product. One good visit with the floor and that header came away, taking all the SMD pads with it. The big boys who build for the world cut corners like this all the time.

The MME has a couple of very heavy PCBs that only attach via headers.

I tend to put spacers in between boards even when there are plenty of headers to hold them. This is mostly about vibration. Under shock or vibration, I would like the entire construction to move as a single mass. Without the supports, you get the situation where shock and vibration are being transmitted from one board to the other, via the solder connections. Solder connections are not designed for this purpose (although may perform fine in some cases).
abelovesfun
I use spacers in my modules that have two pcbs. It's not always needed, but I think it's best practice to do so.
AdrianH
If you have room at the sides you could try something like this.
Might also work without washers.
Could use extra zip tie around spacer pair to lock side movement.
mskala
If it's a one-off project for yourself, okay, mess around with cable ties, glue, do whatever it takes. If it's something you're going to sell, or make more than one time? Redesign the board.
djthopa
mskala wrote:
If it's a one-off project for yourself, okay, mess around with cable ties, glue, do whatever it takes. If it's something you're going to sell, or make more than one time? Redesign the board.


Thanks @ mskala and all for you input.

I think for the next projects i will place drill holes at the beginning of the project so i wont forget about them!
fuzzbass
djthopa wrote:
mskala wrote:
If it's a one-off project for yourself, okay, mess around with cable ties, glue, do whatever it takes. If it's something you're going to sell, or make more than one time? Redesign the board.


Thanks @ mskala and all for you input.

I think for the next projects i will place drill holes at the beginning of the project so i wont forget about them!


The headers most of use are using add up to 11mm clearance. Many projects specify 12mm spacers, but 11 is a better choice and widely available.
JohnLRice
djthopa wrote:
I have been working on a project that has two pcb’s.

I did all the routing inside eagle but forgot to add the 3mm holes for the spacers that separate the two pcbs.

There are 14 pins going from one pcb to the other.

Power cable is on the outside pcb,

Im concerned about pulling the pcbs apart since they are not phisically attached apart from the pins.
If your 14 pin headers are near the edges of the PCBs, once you are done building and trouble shooting etc you could possibly attach a short piece of buss wire (bare wire) between the solder pads of the two boards, preferably using pads that go to the zero volt/ground plane and if they are on the outer edge of the connectors. That way it would be easy to unsolder or clip the wire if you needed to disassemble.
djthopa
JohnLRice wrote:
djthopa wrote:
I have been working on a project that has two pcb’s.

I did all the routing inside eagle but forgot to add the 3mm holes for the spacers that separate the two pcbs.

There are 14 pins going from one pcb to the other.

Power cable is on the outside pcb,

Im concerned about pulling the pcbs apart since they are not phisically attached apart from the pins.
If your 14 pin headers are near the edges of the PCBs, once you are done building and trouble shooting etc you could possibly attach a short piece of buss wire (bare wire) between the solder pads of the two boards, preferably using pads that go to the zero volt/ground plane and if they are on the outer edge of the connectors. That way it would be easy to unsolder or clip the wire if you needed to disassemble.


Hey John thanks for the input, thats a good idea, unfortunately the pins are pretty much in the center of the pcb. Dead Banana
NV
djthopa wrote:

I think for the next projects i will place drill holes at the beginning of the project so i wont forget about them!


Include them as objects in the schematic and associate them with the standoff footprint so they're bunched in as part of routing. Good practice for things that can be easy to forget during layout, like fiducials.
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