Author Topic: OTC "Silasitc"?  (Read 5892 times)

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Offline ender4171Topic starter

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OTC "Silasitc"?
« on: February 04, 2019, 05:26:49 pm »
Dave and others often talk about components being tied down with silastic.  I have found the OG Dow/Corning 732 stuff, but it is pricey and not available in small quantities (way more than I would use in time without it going bad).  Is there anything really special about it other than it is a neutral cure silicone?  I was thinking of grabbing some GE Silicone II, which is also neutral cure and is available at any home store in small tubes.  Does anyone have experience with that product, or have any recommendations for an alternative that is readily available?
 

Online coppercone2

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Re: OTC "Silasitc"?
« Reply #1 on: February 04, 2019, 05:32:24 pm »
Ill give you a cookie if you make mechanical mounts for your parts rather then hosing it down in xenomorph juices
 

Offline ender4171Topic starter

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Re: OTC "Silasitc"?
« Reply #2 on: February 04, 2019, 05:41:42 pm »
Maybe "hold down" was a bad choice of words.  This is for vibration mitigation on things like capacitors.  Hard mounts would of course be ideal, but they aren't practical for small-medium sized parts, especially when the board is densely populated.  I am talking about this sort of thing:

 

Offline wraper

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Re: OTC "Silasitc"?
« Reply #3 on: February 04, 2019, 05:53:06 pm »
Ill give you a cookie if you make mechanical mounts for your parts rather then hosing it down in xenomorph juices
Please show your 'mechanical mounts' for PCB mounted capacitors, transistors, resistors, inductors...  :bullshit:
« Last Edit: February 04, 2019, 05:56:30 pm by wraper »
 
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Offline rdl

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Re: OTC "Silasitc"?
« Reply #4 on: February 04, 2019, 07:12:26 pm »
I'd never heard the term "silastic" until watching EEVblog. I think it just refers to a type of silicone glue that cures to a rubbery state and is non-corrosive. I'm pretty sure a lot of manufacturers just use hot glue of some kind, which is what I do.
 

Offline wraper

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Re: OTC "Silasitc"?
« Reply #5 on: February 04, 2019, 07:28:50 pm »
Hot glue is used rarely and usually only in crappy devices. Usual cheap hot glue will not only melt at elevated temperatures, it will also delaminate in a few years at most. And if vibration or freezing temperature is present it may fail almost instantly. What you normally see is RTV silicone adhesive.
 

Online coppercone2

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Re: OTC "Silasitc"?
« Reply #6 on: February 04, 2019, 07:45:19 pm »
Ill give you a cookie if you make mechanical mounts for your parts rather then hosing it down in xenomorph juices
Please show your 'mechanical mounts' for PCB mounted capacitors, transistors, resistors, inductors...  :bullshit:

you can make them? what do you want me to , bend some thin aluminum bar stock and take pictures of brackets? amazing technology.

here, its photoshopped


you can also make them smaller  :scared:

and yea the best way to actually secure a transistor is to put a bar on it tensioned with screws from the side.
« Last Edit: February 04, 2019, 07:47:58 pm by coppercone2 »
 

Offline wraper

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Re: OTC "Silasitc"?
« Reply #7 on: February 04, 2019, 08:06:09 pm »
Ill give you a cookie if you make mechanical mounts for your parts rather then hosing it down in xenomorph juices
Please show your 'mechanical mounts' for PCB mounted capacitors, transistors, resistors, inductors...  :bullshit:

you can make them? what do you want me to , bend some thin aluminum bar stock and take pictures of brackets? amazing technology.

here, its photoshopped


you can also make them smaller  :scared:

and yea the best way to actually secure a transistor is to put a bar on it tensioned with screws from the side.
LOL, I'd like to see such abysmal PCB where most of smallish inductors and caps are attached with that crap. FYI silicone adhesive works very well against vibration. It's especially useful for single layer PCBs where solder joints are much more prone to cracking. Also I would like to see how production engineer hires an assassin after you submit such design for assembly  :-DD. Oh, and I guess people with trypophobia better to not look on that PCB ridden with mounting holes.
« Last Edit: February 04, 2019, 08:14:15 pm by wraper »
 

Online coppercone2

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Re: OTC "Silasitc"?
« Reply #8 on: February 04, 2019, 08:31:31 pm »
your right about it being considered high quality and high repair ability.  Of course they will dislike the design.

It's also in the beginners forum.

you know you can stamp a big piece of metal to fit over the entire PCB to sandwich everything?

If you buy aluminum bar stock you can cut it with bolt cutters, bend it in a vice with a hammer and drill holes, in a few minutes.

actually faster then curing shit.
« Last Edit: February 04, 2019, 08:35:58 pm by coppercone2 »
 

Offline wraper

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Re: OTC "Silasitc"?
« Reply #9 on: February 04, 2019, 08:50:25 pm »
your right about it being considered high quality and high repair ability.  Of course they will dislike the design.

It's also in the beginners forum.

you know you can stamp a big piece of metal to fit over the entire PCB to sandwich everything?

If you buy aluminum bar stock you can cut it with bolt cutters, bend it in a vice with a hammer and drill holes, in a few minutes.

actually faster then curing shit.
Nor it will be high quality, nor it will have good repairability. It will be hell to disassemble and assemble back. On the other hand you can simply cut silicone adhesive with a knife and remove the component. Not to say your suggestion would have abysmal effect on size and weight.
Quote
you know you can stamp a big piece of metal to fit over the entire PCB to sandwich everything?
The only way it would somewhat work is if you put pieces of elastic material between it and components. Pressing them down and adding mechanical stress on parts and solder joints. Also it would obstruct airflow this preventing heat dissipation. Adhesive on the other hand fixes components in their natural position after soldering and does not add any stress.
IMO you don't know a tiny bit about DFM (design for manufacturability).
 

Online coppercone2

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Re: OTC "Silasitc"?
« Reply #10 on: February 04, 2019, 08:51:42 pm »
its design for prototyping because its a blog and its the beginners forum.

Putting two screws on something is not hell. Having to use a exacto blade is. It's ridiclous.
 

Offline Ice-Tea

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Re: OTC "Silasitc"?
« Reply #11 on: February 04, 2019, 08:55:13 pm »
I'm pretty sure a lot of manufacturers just use hot glue of some kind, which is what I do.

Please don't. Once had a PSU manufacter that also considered it a good idea. The stuff would just run out of the vent holes if you put it upside down..

Offline wraper

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Re: OTC "Silasitc"?
« Reply #12 on: February 04, 2019, 08:55:20 pm »
its design for prototyping because its a blog and its the beginners forum.

Putting two screws on something is not hell. Having to use a exacto blade is. It's ridiclous.
Are you suggesting that if it's beginners section, suggestions should be such that no sane engineer would do that.  |O

Quote
Putting two screws on something is not hell
Putting 2 screws, then multiplied by many tens as minimum  :palm:. And creating custom fixture for every different component.
« Last Edit: February 04, 2019, 08:56:57 pm by wraper »
 

Online coppercone2

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Re: OTC "Silasitc"?
« Reply #13 on: February 04, 2019, 08:57:58 pm »
what no sane engineer would do is put silastic in a 1 off.

chirst it would be so dirty and if you need to rework it you need to peel fucking glue off of everything.
 

Offline wraper

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Re: OTC "Silasitc"?
« Reply #14 on: February 04, 2019, 09:01:20 pm »
what no sane engineer would do is put silastic in a 1 off.

chirst it would be so dirty and if you need to rework it you need to peel fucking glue off of everything.
You don't need to place it on prototype to begin with. It's usually used to prevent damage during transportation. And there is nothing dirty about it. What would be really insane is spending half of your time one making stupid custom fixtures instead of doing what matters.
 

Online coppercone2

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Re: OTC "Silasitc"?
« Reply #15 on: February 04, 2019, 09:04:34 pm »
half your time? really? are you refining your own aluminum or something?

get real. Are you drilling the holes with a sharp stick or are you trying to cut metal with a butter knife here?

absolutely preposterous.
 

Offline wraper

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Re: OTC "Silasitc"?
« Reply #16 on: February 04, 2019, 09:07:39 pm »
half your time? really? are you refining your own aluminum or something?

get real
Feels like logic falling apart when written by you. IMO you should look in the mirror.
 

Online coppercone2

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Re: OTC "Silasitc"?
« Reply #17 on: February 04, 2019, 09:11:29 pm »
your telling my its going to take long to drill a few holes and bend a piece of metal ???

yea half my time
quarter of a cigarette break?
 

Offline wraper

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Re: OTC "Silasitc"?
« Reply #18 on: February 04, 2019, 09:14:25 pm »
your telling my its going to take long to drill a few holes and bend a piece of metal ???

yea half my time
quarter of a cigarette break?
You could solder a whole pcb faster than bending that stupid metal and drilling holes. Also you need to spend a lot of time when designing PCB just to make that those fixtures would fit. Insanity squared  :palm:. Please show an example of actual PCB with this stupid crap.
 
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Online coppercone2

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Re: OTC "Silasitc"?
« Reply #19 on: February 04, 2019, 09:15:16 pm »
 

Offline Nerull

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Re: OTC "Silasitc"?
« Reply #20 on: February 04, 2019, 10:33:12 pm »
OP never specified this was for a one-off, you seem to have made that detail up in your head.

And yes, bolting capacitors to a big piece of metal is moronic. How many expensive custom machined or stamped parts are you going to put on your cheap, one-off board?
 

Online coppercone2

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Re: OTC "Silasitc"?
« Reply #21 on: February 04, 2019, 10:46:25 pm »
ones that you make with a hammer in 5 minutes?

expensive? custom machined? your competing with glue ffs.
« Last Edit: February 04, 2019, 10:48:26 pm by coppercone2 »
 

Offline wraper

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Re: OTC "Silasitc"?
« Reply #22 on: February 04, 2019, 10:51:59 pm »
ones that you make with a hammer in 5 minutes?
And you call that crap better and more elegant than using silicone adhesive? I ask again, show a photo of PCB where your suggestion is actually realized. And not something like a one huge axial cap bolted down while other components are not on PCB from 70's-80's . Not just products of your imagination.
 

Offline RobertHolcombe

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Re: OTC "Silasitc"?
« Reply #23 on: February 04, 2019, 10:57:43 pm »
Someone has had a bad experience with silicone...

Only applied where needed it literally takes 5 seconds to sever/remove with a knife or side cutters. If you are doing rework but don't have either of those but you have metal fabrication tools and spare metal, perhaps crafting a blade from scratch would be more time efficient for you than making custom brackets  ::)
 

Offline timelessbeing

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