I am looking for a source. or even just a proper name for sheets of insulating material often found in amplifiers and the like. I have heard it called "Fish Paper" before but not sure if that is correct. typically the sheets are red or orange-ish in color and flexible. generally thick almost like the back of a notebook but obviously a different material and stronger and im sure a better dielectric.
what the heck do you call this stuff? and where would a person buy it in the US?
OR...flipping the coin to the other side. what would YOU use to say insulate the bottom of a PCB from the bottom of a chassis? or say provide a bit if insulation from a heatsink etc.
Zc
what the heck do you call this stuff? and where would a person buy it in the US?
OR...flipping the coin to the other side. what would YOU use to say insulate the bottom of a PCB from the bottom of a chassis? or say provide a bit if insulation from a heatsink etc.
Zc
I don't like fish paper, as it's too hygroscopic unless it's impregnated with something like varnish. A sheet of drawing mylar would work just fine to insulate a printed circuit board from a chassis. If you want to get creatively cheap, a piece hacked out of the straight side of a plastic gallon jug would also work very well - polyethylene, polypropylene, PET, doesn't matter, all would work ok, and count as creative and productive recycling..
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Like a lacquered fabric?
I know Russian name. Ëàêîòêàíè | Èçîëÿöèîííûå ìàòåðèàëû
I personally use Kapton film under PCBs; I have plenty of it.
I know Russian name. Ëàêîòêàíè | Èçîëÿöèîííûå ìàòåðèàëû
I personally use Kapton film under PCBs; I have plenty of it.
Wavebourn - yeah something like that! I need something that had a bit of dielectric to it. The boards I am working with sit 1/8" above the heatsink and about 1/8" away from the top/bottom of the chassis and have 320V from rail to rail. they are tour duty amplifiers and they have a tendency to arc under some conditions.
For baking cookies in the oven , they use parchment paper .
Also consider silicone baking mats .
Another cheap thought , is a plastic notebook divider .
Also consider silicone baking mats .
Another cheap thought , is a plastic notebook divider .
Ohhhh Silicone baking mats! now that's a creative idea! I like that!
I wonder where Amplifier Mfgs get this stuff??
I wonder where Amplifier Mfgs get this stuff??
Here;
http://www.mcmaster.com/#fishpaper-sheets/=5k2ygu
In the past it was used in transformer construction to cover and protect the lead wire attachments. I have also seen it used to prevent windings from arcing to the lamination stack for VDE rated (4500VRMS) transformers.
Matt
http://www.mcmaster.com/#fishpaper-sheets/=5k2ygu
In the past it was used in transformer construction to cover and protect the lead wire attachments. I have also seen it used to prevent windings from arcing to the lamination stack for VDE rated (4500VRMS) transformers.
Matt
There was a mottled greyish 'paper' around some years ago which had some sort of sulphide/sulphate impregnation which was very very good; it was originally used in the computer industry. It also had good dielectric properties. The down side of most plastics is that they have poor dielectric quality and are prone to stray capacitance problems; polyethylene is probably the very best.
Exactly as soundchaser wrote!
From my 1970 electronics dictionary:
Fishpaper
A tough fiber used in sheet form for insulating transformer windings from the core, field coils from the field poles, or conductors from the armature.
From my 1970 electronics dictionary:
Fishpaper
A tough fiber used in sheet form for insulating transformer windings from the core, field coils from the field poles, or conductors from the armature.
Ok so I'm not crazy(well...that i guess is yet to be determined but i wasn't wrong) they do call it fish paper!
Plastic has a tendency to melt under high heat. should an arc happen, the plastic would just melt. but this fishpaper stuff seems to be pretty tough. I have an amp here that literally started on fire and that thick fishpaper stuff toughed it out pretty well considering the damage to the PCB.
I still like the silicon baking sheet idea. Target stores sell 12"x16" flat sheets for $10 so its not cheap but would offer a bit of cushioning in some instances. But one amplifier i work on, I need a stiff sheet to slid in between two heatsinks after installation so the silicon sheets wont work for that.
Plastic has a tendency to melt under high heat. should an arc happen, the plastic would just melt. but this fishpaper stuff seems to be pretty tough. I have an amp here that literally started on fire and that thick fishpaper stuff toughed it out pretty well considering the damage to the PCB.
I still like the silicon baking sheet idea. Target stores sell 12"x16" flat sheets for $10 so its not cheap but would offer a bit of cushioning in some instances. But one amplifier i work on, I need a stiff sheet to slid in between two heatsinks after installation so the silicon sheets wont work for that.
This is the industry standard today.
Synflex Elektro GmbH: NOMEX ® Type 410
Very tough and heat resistant.
Magura 🙂
Synflex Elektro GmbH: NOMEX ® Type 410
Very tough and heat resistant.
Magura 🙂
for the bottom of pcb, an electronic "varnish" coat is a good idea. I would presume that arcing as you describe is in part due to humidy, so coating the board itself will eliminate that source... they also sell a spray on clear acrylic dielectric coating as well...
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In one of the amplifiers i worked on. has two electrically live heatsinks one suspended above the other with an 1/8" gap between them. each sink can have close to 160V on each, 320V across them. compression of the top and bottom of the amp causes the brackets that hold the heatsinks apart to bend and the sinks then to touch! BZZZT.
in one instance a wasp flew in the back of the amp and got between the sinks and started the arc. In another amp, an axial capacitor either failed or the PCB conformal coating failed and an arc was formed between the cap body and a trace below it. this melted a hole in the cap and caused charring of the PCB, the arc literally "mined" it's way under traces to a screw that held the PCB to the sink. other areas of the board had arcing from transistor legs to the heatsink. and under the PCB to the heatsink and it literally melted big holes in the aluminum sinks! made a real mess!
So i removed the axial caps and put some fish paper under them. I used a piece that was removed from a scrap amp but now i would like to put a larger piece under the PCB and strips under the transistor legs. The amp is expected to fail in the future. this sound company seems to blew a few up every year and maybe i can protect the vital area's enough so that there is less damage the next time it is repaired.
in one instance a wasp flew in the back of the amp and got between the sinks and started the arc. In another amp, an axial capacitor either failed or the PCB conformal coating failed and an arc was formed between the cap body and a trace below it. this melted a hole in the cap and caused charring of the PCB, the arc literally "mined" it's way under traces to a screw that held the PCB to the sink. other areas of the board had arcing from transistor legs to the heatsink. and under the PCB to the heatsink and it literally melted big holes in the aluminum sinks! made a real mess!
So i removed the axial caps and put some fish paper under them. I used a piece that was removed from a scrap amp but now i would like to put a larger piece under the PCB and strips under the transistor legs. The amp is expected to fail in the future. this sound company seems to blew a few up every year and maybe i can protect the vital area's enough so that there is less damage the next time it is repaired.
another cheep and useful thought .
raw 1/8 FR4 PCB ( no copper )
google its properties .
a wasp can't fly between a 1/8 gap if it doesn't exist !
raw 1/8 FR4 PCB ( no copper )
google its properties .
a wasp can't fly between a 1/8 gap if it doesn't exist !
if you don't need to get them apart often and you don't need the gap for cooling, then silicone rubber the gap... you only need to cover the entrance side if it is bug proofing...
but, word to the wise, don't fix things too well if your job is fixing, unless there is far far too much to ever fix...
but, word to the wise, don't fix things too well if your job is fixing, unless there is far far too much to ever fix...
Ah, yes, the smell of smoldering fish paper in the morning. Brings back memories of my unit-test days!
I like the silicone mat idea. But the paper was also very tough against punch through to protect sharp edges. Tansformers had a layer of it between the winding and core to soften the sharp edges of the core. You want it tough because of the micro-vibrations. I would be afraid silicone would cut or cold-flow. How about fiberglass mat? Most newer windings are done on a plastic bobbin eliminating the problem.
I like the silicone mat idea. But the paper was also very tough against punch through to protect sharp edges. Tansformers had a layer of it between the winding and core to soften the sharp edges of the core. You want it tough because of the micro-vibrations. I would be afraid silicone would cut or cold-flow. How about fiberglass mat? Most newer windings are done on a plastic bobbin eliminating the problem.
Grocery Bags!
Years ago WEST Epoxy built a sailboat out of brown wrapping paper laminated with their epoxy. Apparently very strong and light. What does this have to do with "fish paper"? Not much... But what if you used some varnish and laminated 4 or 5 sheets of grocery store paper bag? Would that take care of your arcing and fill the void?
Just a thought,
Dr. Spiff
Years ago WEST Epoxy built a sailboat out of brown wrapping paper laminated with their epoxy. Apparently very strong and light. What does this have to do with "fish paper"? Not much... But what if you used some varnish and laminated 4 or 5 sheets of grocery store paper bag? Would that take care of your arcing and fill the void?
Just a thought,
Dr. Spiff
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