Cooling plate came off my 80HV

[Andy from Sandy]

I use this stuff myself

Buy Thermal Adhesives Thermal bonding epoxy adhesive,20ml Electrolube ERTBS20S online from RS for next day delivery.

[bpgoa]

Ok. To report back.

Had a look at the ESC. The FETs are potted in the plastic that the case is made of so none of the board visible. The top of the FETs had quite a thick layer of a thermal epoxy on top of them that was used to bond the thin alloy plate on. The reason that this glue bond is so thick is down to the moulding of the case leaving the FETs quite a way from the cases surface. IMHO, not a very good design, but who am I to question Kontronic.

I just looked up the glue that Andy above uses and it is an excellent choice for this application.

We have decided not to bond a new plate back in and to bond the heatsink straight in.... No point in having two thermal isolation junctions in the heatsink pathway. That would be silly.

So we have cleaned the old epoxy off the top of the FETs, filed the bottom of the heatsink flat ( these type of extrusions usually have a slight warp across them and intend to bond this directly onto the top of the FETs. Once the glue arrives.

[brin]

as you say Adrain Not a good idea as it sounds like the extra layer could keep the heat in.What glue have you used.

[mattscupoftea]

Unfortunately (and with a little embarrassment) I have to report back in. . .

Adrian's help with the ESC was great, and greatly received. An hour or so of painstaking cotton bud application of epoxy thinner, and gentle scraping with a cocktail stick or two under his watchful eye led to the exposure of eighteen shiny silver FETs. I then took that home, ordered some arctic silver and waited patiently for it to arrive.

A couple of days later, I applied the arctic silver carefully to each FET with two cocktail sticks (not an easy procedure - the adhesive doesn't want to come off your applicator in nice neat packages, rather it stretches like hot glue and attempts to make a mess everywhere, causing you to have to try to break the stringy residue from the applicator in a hurry as you have 15 more to do in the next two minutes before the stuff sets!) and pressed the heatsink into position with some dense foam on either side and a G-clamp.

A couple more days later (after a little work jaunt to Sweden - more time away from flying!) and I was in a position to connect up the ESC. I did so, and within about eight seconds, a 15cm flame-ball appeared and the heatsink looked somewhat charred.

FAILURE

On examination, the thermal adhesive had spread (I know - exactly what I was being careful to try not to do!) and arctic silver being conductive, I think it might have caused some problems. Perhaps the epoxy thinner had also thinned the casing around the FETs and allowed the arctic silver to seep down to the contacts? Anyhow, a rather embarrassed failure.

It has been suggested that Kontronik may, possibly, maybe, be able to offer me a slightly cheaper than new replacement for my toasted unit. I would be fully honest with them if I sent it in, and see what happens. I guess there's no reason not to try, unless anyone knows it will be a definite no from them and a waste of postage.

Until then, I am looking into possibilities to get into the air with advice from fellow members.

Thanks all for your help, and sorry to let you down with poor application of said advice!

[Andy from Sandy]

Maybe a lesson for others there.
The Electrolube epoxy is an electrical insulator

Thermal Bonding Compound is a metal oxide loaded two part epoxy bonding system with excellent thermal conductivity properties whilst being electrically insulating.

[Rob Barnes]

I had this happen a few months ago and sorry im late on the thread. I used artic silver on mine and glued it back in with no problems at all. Although mine cam off during a crash !

[mattscupoftea]

All good. I'm going to take the hobbywing/turnigy esc route and have a go with the vbar governor this time rather than fork out for another jive. I liked the plug and playness of the jive and it did a great job but also like the idea of this other route. Also this means I will be using a LiFe pack rather than bec. Fingers crossed!

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