Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
Not the usual nylon or whatever ones that I never trust for high
temperatures (soften and deform over time, loosening thermal connection,runs hotter, melts more ...... Does anyone make them from whatever the plastic/mineral? is used for the body of power transistors themselves, what is that material , what is it called? . Maybe because of brittleness they would have to use smaller screws/bolts allowing larger washer thickness in the hole. I've got in the habit of cutting off the non-metal mounting parts of TOP66 type transistors, opening the holes of TO220 or TOP3 and using them as washers. Or any other solution, modification? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#2
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
N Cook wrote in message
... Not the usual nylon or whatever ones that I never trust for high temperatures (soften and deform over time, loosening thermal connection,runs hotter, melts more ...... Does anyone make them from whatever the plastic/mineral? is used for the body of power transistors themselves, what is that material , what is it called? . Maybe because of brittleness they would have to use smaller screws/bolts allowing larger washer thickness in the hole. I've got in the habit of cutting off the non-metal mounting parts of TOP66 type transistors, opening the holes of TO220 or TOP3 and using them as washers. Or any other solution, modification? a pic of the usual low temp plastic insulating bushes http://www.maplin.co.uk/images/300/rn91.jpg That 3.5 - 3.1 or 3.9 - 3.1mm dimension, divided into two, internal section, would probably be too breakable with that power transistor body material, if direct replacements -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#3
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
On Mar 2, 1:23*am, "N Cook" wrote:
Not the usual nylon or whatever ones that I never trust for high temperatures... Mounting 'kits' for power transistors cost more than many of the transistors themselves (over a dollar for a mica gasket and some screws and washers). You can cut a small length of PTFE (Teflon) tubing for the machine screw shaft, and use a piece of fiberglass-reinforced plastic (FRP) as a washer to hold off the head, I've used polyimide (Kapton) tape for the heatsink insulation barrier. I'm not sure where my FRP washers came from, but the Teflon tubing, about gauge #9 for 4-40 screws, is a common laboratory supply item. |
#4
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
whit3rd wrote in message
... On Mar 2, 1:23 am, "N Cook" wrote: Not the usual nylon or whatever ones that I never trust for high temperatures... Mounting 'kits' for power transistors cost more than many of the transistors themselves (over a dollar for a mica gasket and some screws and washers). You can cut a small length of PTFE (Teflon) tubing for the machine screw shaft, and use a piece of fiberglass-reinforced plastic (FRP) as a washer to hold off the head, I've used polyimide (Kapton) tape for the heatsink insulation barrier. I'm not sure where my FRP washers came from, but the Teflon tubing, about gauge #9 for 4-40 screws, is a common laboratory supply item. reply: I've plenty of sources of PTFE suitable for the insert part but no known sourse of suitable FRP. I wonder if fibre reinforced phenolic board would be suitable for the washer, I'll try heating some. Of course that washer part does not have to be circular and cutting it square with a hole would be easier. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#5
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
N Cook wrote in message
... whit3rd wrote in message ... On Mar 2, 1:23 am, "N Cook" wrote: Not the usual nylon or whatever ones that I never trust for high temperatures... Mounting 'kits' for power transistors cost more than many of the transistors themselves (over a dollar for a mica gasket and some screws and washers). You can cut a small length of PTFE (Teflon) tubing for the machine screw shaft, and use a piece of fiberglass-reinforced plastic (FRP) as a washer to hold off the head, I've used polyimide (Kapton) tape for the heatsink insulation barrier. I'm not sure where my FRP washers came from, but the Teflon tubing, about gauge #9 for 4-40 screws, is a common laboratory supply item. reply: I've plenty of sources of PTFE suitable for the insert part but no known sourse of suitable FRP. I wonder if fibre reinforced phenolic board would be suitable for the washer, I'll try heating some. Of course that washer part does not have to be circular and cutting it square with a hole would be easier. The washer part could be a disc or 2 of that stiff plastic material found inside power supplies where there is a chance that some component will touch the casing, next to a steel washer under the bolt/screw head. For that matter I don't see a problem of using a mica disc or 2 then a steel washer for that part. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#6
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
On Sun, 2 Mar 2008 20:55:26 -0000, "N Cook" wrote:
:N Cook wrote in message ... : whit3rd wrote in message : ... : On Mar 2, 1:23 am, "N Cook" wrote: : Not the usual nylon or whatever ones that I never trust for high : temperatures... : : Mounting 'kits' for power transistors cost more than many of : the transistors themselves (over a dollar for a mica gasket : and some screws and washers). You can cut a small length of : PTFE (Teflon) tubing for the machine screw shaft, and use a : piece of fiberglass-reinforced plastic (FRP) as a washer to hold off : the head, I've used polyimide (Kapton) tape for the heatsink : insulation barrier. : : I'm not sure where my FRP washers came from, but the : Teflon tubing, about gauge #9 for 4-40 screws, is a common : laboratory supply item. : : reply: : I've plenty of sources of PTFE suitable for the insert part but no known : sourse of suitable FRP. I wonder if fibre reinforced phenolic board would :be : suitable for the washer, I'll try heating some. Of course that washer part : does not have to be circular and cutting it square with a hole would be : easier. : : : :The washer part could be a disc or 2 of that stiff plastic material found :inside power supplies where there is a chance that some component will touch :the casing, next to a steel washer under the bolt/screw head. :For that matter I don't see a problem of using a mica disc or 2 then a steel :washer for that part. Richco make a high temperature shoulder washer designated MNI-HT http://www.richco-inc.com/group_deta...&grpcode=A2390 The #4-220 is designed for the TO220 transistor mounting hole. |
#7
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
N Cook wrote: Not the usual nylon or whatever ones that I never trust for high temperatures (soften and deform over time, loosening thermal connection,runs hotter, melts more ...... I can't say I've ever seen that myself. Does anyone make them from whatever the plastic/mineral? is used for the body of power transistors themselves, what is that material , what is it called? You mean Mica. It's a natural mineral. And no, transistor bodies aren't made from mica btw. http://uk.farnell.com/jsp/search/bro...tt= mica&Ntx= Graham |
#8
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
N Cook wrote: Not the usual nylon or whatever ones that I never trust for high temperatures (soften and deform over time, loosening thermal connection,runs hotter, melts more ...... Oh, the washer themselves ? No, I've only ever seen nylon ones. You simply need to do them up tight with lockwashers. Personally, I prefer mounting devices 'live' or using spring clips to retain them. Graham |
#9
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
N Cook wrote: Does anyone make them from whatever the plastic/mineral? is used for the body of power transistors themselves, what is that material , what is it called? . Maybe because of brittleness they would have to use smaller screws/bolts allowing larger washer thickness in the hole. Mica would simply crush. Delrin would be nice but I don't know of anyone making washers in that. Another way is to use nylon screws. I've got in the habit of cutting off the non-metal mounting parts of TOP66 type transistors, opening the holes of TO220 or TOP3 and using them as washers. What on earth do you mean ? Graham |
#10
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
Ross Herbert wrote in message
... On Sun, 2 Mar 2008 20:55:26 -0000, "N Cook" wrote: :N Cook wrote in message ... : whit3rd wrote in message : ... : On Mar 2, 1:23 am, "N Cook" wrote: : Not the usual nylon or whatever ones that I never trust for high : temperatures... : : Mounting 'kits' for power transistors cost more than many of : the transistors themselves (over a dollar for a mica gasket : and some screws and washers). You can cut a small length of : PTFE (Teflon) tubing for the machine screw shaft, and use a : piece of fiberglass-reinforced plastic (FRP) as a washer to hold off : the head, I've used polyimide (Kapton) tape for the heatsink : insulation barrier. : : I'm not sure where my FRP washers came from, but the : Teflon tubing, about gauge #9 for 4-40 screws, is a common : laboratory supply item. : : reply: : I've plenty of sources of PTFE suitable for the insert part but no known : sourse of suitable FRP. I wonder if fibre reinforced phenolic board would :be : suitable for the washer, I'll try heating some. Of course that washer part : does not have to be circular and cutting it square with a hole would be : easier. : : : :The washer part could be a disc or 2 of that stiff plastic material found :inside power supplies where there is a chance that some component will touch :the casing, next to a steel washer under the bolt/screw head. :For that matter I don't see a problem of using a mica disc or 2 then a steel :washer for that part. Richco make a high temperature shoulder washer designated MNI-HT http://www.richco-inc.com/group_deta...&grpcode=A2390 The #4-220 is designed for the TO220 transistor mounting hole But that is also nylon, just because they call it high temperature, does not necessarily mean it does not compress/creep in normal but highly elevated temperatures, leading to premature failure of device. The point is I'm after some insulated and mechanically strong enough alternative to plastic without having to drill into heatsinks for spring retention. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#11
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
N Cook wrote:
Ross Herbert wrote in message ... On Sun, 2 Mar 2008 20:55:26 -0000, "N Cook" wrote: :N Cook wrote in message ... : whit3rd wrote in message : ... : On Mar 2, 1:23 am, "N Cook" wrote: : Not the usual nylon or whatever ones that I never trust for high : temperatures... : : Mounting 'kits' for power transistors cost more than many of : the transistors themselves (over a dollar for a mica gasket : and some screws and washers). You can cut a small length of : PTFE (Teflon) tubing for the machine screw shaft, and use a : piece of fiberglass-reinforced plastic (FRP) as a washer to hold off : the head, I've used polyimide (Kapton) tape for the heatsink : insulation barrier. : : I'm not sure where my FRP washers came from, but the : Teflon tubing, about gauge #9 for 4-40 screws, is a common : laboratory supply item. : : reply: : I've plenty of sources of PTFE suitable for the insert part but no known : sourse of suitable FRP. I wonder if fibre reinforced phenolic board would :be : suitable for the washer, I'll try heating some. Of course that washer part : does not have to be circular and cutting it square with a hole would be : easier. : : : :The washer part could be a disc or 2 of that stiff plastic material found :inside power supplies where there is a chance that some component will touch :the casing, next to a steel washer under the bolt/screw head. :For that matter I don't see a problem of using a mica disc or 2 then a steel :washer for that part. Richco make a high temperature shoulder washer designated MNI-HT http://www.richco-inc.com/group_deta...&grpcode=A2390 The #4-220 is designed for the TO220 transistor mounting hole But that is also nylon, just because they call it high temperature, does not necessarily mean it does not compress/creep in normal but highly elevated temperatures, leading to premature failure of device. The point is I'm after some insulated and mechanically strong enough alternative to plastic without having to drill into heatsinks for spring retention. MEC make thermoplastic transistor insulators that are rated up to 180c continuous. Farnell sells them. Ron(UK) -- Lune Valley Audio Public Address Systems Hire Sales Maintenance www.lunevalleyaudio.com |
#12
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
On Mon, 3 Mar 2008 08:07:40 -0000, "N Cook" wrote:
SNIP : : :But that is also nylon, just because they call it high temperature, does not :necessarily mean it does not compress/creep in normal but highly elevated :temperatures, leading to premature failure of device. :The point is I'm after some insulated and mechanically strong enough :alternative to plastic without having to drill into heatsinks for spring :retention. Not all nylons are the same as you know. The normal nylon 6/6 from which the ordinary items are made should not be used over 49C but the items I mentioned are designed to operate up to 200C. If you did some research on the material Polyphenylene Sulfide from which the Richco product is made you would find the following; ... Plastic parts for SMD components are made of PPS (Polyphenylene sulfide) ... which is a high temperature material suitable for reflow soldering profiling. ... Temperature of operation: 200 ..C ... Flammability conformance : As per UL 94 V-O |
#13
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
Ross Herbert wrote in message
... On Mon, 3 Mar 2008 08:07:40 -0000, "N Cook" wrote: SNIP : : :But that is also nylon, just because they call it high temperature, does not :necessarily mean it does not compress/creep in normal but highly elevated :temperatures, leading to premature failure of device. :The point is I'm after some insulated and mechanically strong enough :alternative to plastic without having to drill into heatsinks for spring :retention. Not all nylons are the same as you know. The normal nylon 6/6 from which the ordinary items are made should not be used over 49C but the items I mentioned are designed to operate up to 200C. If you did some research on the material Polyphenylene Sulfide from which the Richco product is made you would find the following; .. Plastic parts for SMD components are made of PPS (Polyphenylene sulfide) .. which is a high temperature material suitable for reflow soldering profiling. .. Temperature of operation: 200 ..C .. Flammability conformance : As per UL 94 V-O The point of this thread is not the ultimate melting temperature but the property of not creeping/deforming at sustained elevated temps of say 100 to 120 deg C. eg PTFE would be fine for the internal sleeve part of such bushes unless having to resist abnormal lateral forces. But it would it be reliable as the washer part. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#14
Posted to sci.electronics.repair
|
|||
|
|||
TO220 , TOP3 etc mounting washers ?
On Tue, 4 Mar 2008 10:10:55 -0000, "N Cook" wrote:
: :The point of this thread is not the ultimate melting temperature but the roperty of not creeping/deforming at sustained elevated temps of say 100 to :120 deg C. :eg PTFE would be fine for the internal sleeve part of such bushes unless :having to resist abnormal lateral forces. But it would it be reliable as the :washer part. One of the structural properties of PPS is "brittleness", which would indicate resistance to deformity. But don't take my word for it, take a look at a typical fibereglass filled PPS datasheet http://www.rtpcompany.com/info/data/1300/RTP1379.htm in particular the mechanical and thermal properties. If these figures aren't good enough for you then any other superior solution is not likely to be readily available off-the-shelf. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Tap Washers | UK diy | |||
wheel mounting on play structure mounting questions? | Home Repair | |||
Testing two TO220 recifiers... | Electronics Repair | |||
Tap washers | UK diy | |||
Source for GOOD bolts, washers, copper washers, etc? | Metalworking |