As the title states, where do I buy insulation sheet for insulation between boards and cases (where I would like to have a smaller barrier than the normal 6mm CE creepage distance)? It doesn't have to be thermally conductive for this application of course.
/U.
/U.
The real stuff is called "fishpaper" and if you google that you will find a lot about it.
But I guess it also depends upon the voltages we are dealing with. Some 9v circuit might be happy with a sheet of clear plastic from an office supply. Or cut pieces to fit from empty milk jugs.
But I guess it also depends upon the voltages we are dealing with. Some 9v circuit might be happy with a sheet of clear plastic from an office supply. Or cut pieces to fit from empty milk jugs.
If you need material with official safety ratings, these links may give you information that leads to a source close to home:
http://www.digikey.com/product-search/en?x=0&y=0&lang=en&site=us&KeyWords=fishpaper&stock=1
http://www.mcmaster.com/#fishpaper/=rcqzzi
Over the years I have used quite a few materials for this purpose. Auto parts suppliers stock sheet gasket material of various types and thicknesses, including paper- and synthetic-rubber based material. If I was concerned about contact with a metal chassis, I have cut plastic sheet materials to size and attached them to the chassis surface in susceptible areas. Here in the U.S., hobby, hardware and "home center" stores typically carry acrylic (brandnames include Plexiglass and Perspex), and/or polycarbonate (brandnames include Lexan) sheet in various thicknesses intended for picture frames, window glazing, etc. Polystyrene sheets are sold as fluorescent light diffuser panels. (The material is usable as insulating sheet even if it's textured on one side.) I use double-sided "carpet tape" to adhere the sheets to the chassis surfaces.
Dale
Thanks, I'll take a look at these links 🙂
Enzo: You're right that the application matters. It's specifically for mains isolation (EU, so 240VAC). The normal CE spec is 6mm air between mains parts and chassis, but this can be reduced (for e.g. 1U cases) to 3mm + an insulating layer to provide the extra lavel of protection.
/U.
Enzo: You're right that the application matters. It's specifically for mains isolation (EU, so 240VAC). The normal CE spec is 6mm air between mains parts and chassis, but this can be reduced (for e.g. 1U cases) to 3mm + an insulating layer to provide the extra lavel of protection.
/U.
I'm specifically look for the old insulating cardboard with an adhesive backing. I remember this stuff from my old Heathkit building days and now I have a need to stock a little and use on a current project. As I recall, the little sheets I got with kits were rather stiff and greyish looking in color with peel off back. I was just looking around eBay and it can be found under Fishpaper, but none of it looks exactly like what I prefer. 🙂
Rick
Rick
That material may no longer be available, but Nomex is the standard.
http://www.dupont.com/products-and-...ation/brands/nomex-electrical-insulation.html
The fishpaper is the stuff, even if it is not cut to shape. You can use two-sided tape or some contact cement to mount it in the unit.
Are you objecting to the color?
Are you objecting to the color?
🙂 Color not an issue. I was just trying to describe what I had used years ago. I'll look into Fishpaper.
I'd use NEMA CE or LE laminate, personally. Available in the USA from mcmaster.com and other industrial supply houses. A brown material of stacks of canvas or linen cloth, filled with phenolic. Available in sheets blocks and rods. Other trade names used over the years are garolite, textolite. See this McMaster-Carr
Notice the G9 electrical grade also available on that page. It is harder to thread and more expensive, but if you are going before a rating agency, I suppose you have to use that one. For home work I like CE grade, it is cheap and cuts drills and threads easily. CE could absorb water if you are out at sea like on an island or peninsula, or in marine electronics. I don't like glass filled products, they can be thinner and are more insulating, but wear out drills and saw blades. Glass filled material also makes nasty silicon filled dust. a professional grade vacuum and filter system is required to work it safely. CE makes canvas dust, which the cilia in your lungs can handily eject.
Notice the G9 electrical grade also available on that page. It is harder to thread and more expensive, but if you are going before a rating agency, I suppose you have to use that one. For home work I like CE grade, it is cheap and cuts drills and threads easily. CE could absorb water if you are out at sea like on an island or peninsula, or in marine electronics. I don't like glass filled products, they can be thinner and are more insulating, but wear out drills and saw blades. Glass filled material also makes nasty silicon filled dust. a professional grade vacuum and filter system is required to work it safely. CE makes canvas dust, which the cilia in your lungs can handily eject.
I have kept some rectangular 1 litre yoghurt cartons.
The sides makes nice thick/stiff insulating board to protect from touching mains on the back of PCBs or between mains and close up LV PCBs.
The lids are a much thinner version, but possibly a different plastic.
The sides makes nice thick/stiff insulating board to protect from touching mains on the back of PCBs or between mains and close up LV PCBs.
The lids are a much thinner version, but possibly a different plastic.
I have used cardboard from milk containers in the past too. Having a waxy finish helps its low voltage insulating properties. I am just looking for something that has an adhesive back that comes in sheets easily cut to size.
A little tip, if you have to do a board with voltages on and can afford to do it on a 4 layer board, put all the high voltage stuff on the inner layers and you can go down to 0.4mm gaps and don't have to worry about creepage and clearance.
The dust from the canvas products is dangerous, worked with it before it is not good for you.
I like to use "Silpad 400" from Berquist. Comes in 12"x12" sheets with adhesive backing. Insulation is rated at 4kV. Not cheap though. E
Nomex is the electrical standard,
Or use PCB cut to size, if you want a plastic that's not rated use a motorcycle helmet visor.
Or use mylar sheet lots of it on Ebay.
Mylar is used in Xray equipment.
Regards
M. Gregg
Or use PCB cut to size, if you want a plastic that's not rated use a motorcycle helmet visor.
Or use mylar sheet lots of it on Ebay.
Mylar is used in Xray equipment.
Regards
M. Gregg
Nomex is nice stuff, but pricey. Another alternative is ITW formex, which is flame-retardant polypropylene sheet. It doesn't absorb moisture. Crease it, and it holds the shape - it's also easy to cut and punch.
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