heatsink idea

[sakis]

Most of my amps are based on L shape 4.5mm aluminioum corner that then is attached to the heatsink with bolts and screws ......

In between always and of course is as much paste is possible to ensure better heat transfer from one element to the other.

(Many times crossed my mind to make my own paste made out of the normal white paste we buy at the hardware shops but mixed with aluminioum powder which i can have plenty from local aluminioum shops . Never tryied that but sounds like a good idea )

One other thing i know very well is that not all L shape aluminioum is good to be a heatsink since it is very importand what material is actually made of .

And finally specially made L shape are sold in shops with the iner corner rounded which quicker transfers heat to the main heatsink.

The idea crossed my mind lately is to weld the L to the main heatsink ......since i can do that now i will give it a try and let you know .

In between idlike to listen to your opinion about that



one will say why not buy ready made heatsink that is already shaped to meet your standards ....Then i have to answer that i have so much hetasink in my shop from various projects that i have to convert to fit any amp i construct, and also there is so much heatsink from classic 2N3055 style transistors and i really like to make this usefull again by welding parts on it so it can be used for other devices also

[lineup]

good idea, sakis
how is thing in greece & makedonia ...

Using L-shaped aluminum bars has been used many times
for TO-3 devices this is one of the best ways

in my country of sweden, and in other parts of EUROPE,
www.elfa.se
they sell the follwing special bars
specially made for TO-3 or other transistors

They come in two lengths:
- 80 mm wide, either drilled for 2 x TO-3
or not drilled any holes
- 160 mm wide, predirlled for 4 x TO-3
or un-drilled

[lineup]

These are the dimension
of the L-shaped brackets.
These www.elfa.se will sell to anyone in Europe.

Manufacturer: Austerlitz

L shape bracket to provide heat conducting connection between transistors and heatsink. Undrilled, or drilled for transistors and heatsink.
Material: Aluminium, black anodised.

ELFA is one of the largest catalogue distributors of electronics in Northern Europe
ELFA's experience as an electronics supplier spans 60 years.

The concept of simple ordering and fast and reliable delivery, in combination with an active development of our assortment and extensive technical advise, has made this company into one of the largest catalogue distributors of electronics in northern Europe.

ELFA is owned by the Swiss industry concern Dätwyler.
Our business area includes Sweden, Norway, Denmark, Finland
and Poland, the Baltic States and the Ukraine.

In a further ten European countries ELFA is represented by resellers.

One supplier — more than 65 000 products
ELFA offers a wide selection of the latest news as well as more unusual products. We co-operate with about 650 leading suppliers across the world, selecting products that meet our customers' needs.

[sakis]

all is fine here ..... i actually visited this shop in person i think it should be located in a place called solna but may be i am wrong .....( i visited in 1994)

A think i didnt like about the shop is that works with catalogs and a piece of paper that you write down numbers from the catalog and then somebody will bring it out from the stock .....

Shoping parts in greece is a totaly diferent game .....In the shops you go the "tellers" are edjucated and highly expirienced people in electronics and they know replacements by hurt ( often they dont need to open a book ) then you can also talk about the quality or specs of the product and of course and more importand there you will meet others that share simular needs ,problems, and so on .....so you can talk about your project there ......

May be takes more time but hell !!! shoping is much more fun like that

[AndrewT]

6mm aluminium Tbar is probably better than 6mm L and both will be better than 4.5mm L

[Bonsai]

Sakis,

throw out the L bracket - it adds additiopnal thermal resistance that is not needed and there is a more elegant way of solving this problem.

1. Use TO247 style or TO220 output devices
2. Mount the devices between the PCB and the heatsink.

This solves a lot of mechanical issues and is a quick and neat way to assemble

[sakis]

most times i look at your posts there is always a usefull comment or information .....

this is ok if you need to construct one amp then you had the chance to design like this which is not a bad idea ( but actually eventhough seen it before i have second thoughts on what happens to the pcb if the transistors warm up more than they suppose to ****read my signature *****)

in my case i have right infront of me .....today about 15 amps either to be repaired reconstructed ....others constructed from scratch ....some of them are mine and they are to be repaired and then back to work in small PA rentals that i deal with and then some more amplifiers that are constructed for costumers on special demands and requests .... and a couple of projects that are other peoples ideas which i mod to my taste ....

so with all this volume of work and also all this stock of various heat sink the ability of flexible is a must .....

i ll post pictures any day now about this ....but first i need to make thermo tests

the question remains :

if the L shape will perform beter with paste bolts and screws or welding

[Nordic]

Sakis, you make a mistake if you apply too thick paste...

The easiest way to show you is to do it on a computer CPU chip... as it has digital temperature tracking on your screen...

The trick is to use a high quality thermal compound... the quality computer brands do very well...in terms of how long it lasts, espicialy when applied as thin as possible as per recommendation...

If you can make a copper mounting plaste I suggest you try Coollaboratory Liquid Pro, it will eat aluminium if it gets in contact with it though... this stiuff has 10 times the thermal transfer rate of traditional thermal compounds...

[sakis]

i am aware of that but still this doesnt answer my original question

suppose you need to attach L shaped to a heat sink what is the best way ????

a) bolts and screws tighten up and paste in between ???
B) welding the Lshaped on the big heat sink ????

[MJL21193]

Originally posted by sakis

if the L shape will perform beter with paste bolts and screws or welding

Welding aluminum is tricky - you need shielding gas and the parts need to be heated up before you start or they could warp.

If you can weld aluminum cleanly, welding will be the best way. Welding would connect the metal parts together without a joint between, just continuous metal.