Solder mask and heat?

n me.

not grounded), as a base for a couple of those adhesive backed led strips that I mount on it. Had the boards done and there is solder mask covering t hose areas, which can be easily fixed but it may not matter at all. Just di d the areas for any (tidbit) of added heat dissipation but probably best to let it go to straight plated copper area than a layer of solder mask in be tween?

of it ?

There are at least two effects to consider. One is that the solder mask la yer acts as an insulator. Since it is pretty thin this should not be a lar ge effect. The other is the emissivity of the solder mask vs. the copper/t inning/gold surface layer you would otherwise have. I would expect the sol der mask to have better emissivity. Which is greater? Beats me, but I'm b etting on the emissivity being a larger factor.

--

  Rick C. 

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Easy calculation. Look up the product, find its thermal conductivity, and find the typical application thickness (LPI soldermask, typically around a mil). Plug the numbers into Google Calculator to do whatever unit conversion for you if need be. And there you go.

I think you will find the tape is dominant, unless it's specifically a thermally conductive type. But that the air is even more dominant still

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website:

For moderately high temperatures in still air, it's a measurable difference (if not a significant one). 2-10% range.

I would also be more concerned about the bond strength, as cheap proto glossy mask tends to be not as strong as full spec usually-matte mask is.

Conversely, how does that compare with the strength of the adhesive? Sticky tape on shiny metal tends to not be very good. Sticky tape on plastic tends to be better.

I don't think I've ever had even VHB tape pull mask off a proto board, so it should be good enough either way.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
Website: https://www.seventransistorlabs.com/

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I didn't read the OP well enough and didn't realize this was a contact moun t through the solder mask. So emissivity is pretty irrelevant and given th e other layers involved, I think the solder resist thermal resistance will be in the noise given the thickness and the area involved.

--

  Rick C. 

  + Get 1,000 miles of free Supercharging 
  + Tesla referral code - https://ts.la/richard11209

"Tim Williams" wrote in news:qdtvfr$evm$ snipped-for-privacy@dont-email.me:

I would make a small, copper strip stand off and solder that onto the PCB pad, thereby placing an air gap between the heat sources and the PCB and that air (and thicker Copper) would definitely dissipate better than putting them onto the PCB. You could even make smaller ones that only carry one or two of the LEDs each and they would then be separate little stands and be better mechanically.

Any thick Copper foil or hobby shop sheet material. It would only add a few mm to the profile height. The air gap is the primary cooling gain. Otherwise the PCB should be fine.

IOW, if heat is a problem, he wants a method such as that which I describe. If he is simply trying to max out thermal transfer when the devices never will exhibit much to speak of anyway, the PCB is fine mask or not.

Find some old thrown out motherboards with Copper heat sinks still on them. Those thin fins are great for repurposing for protos.

Machined Copper is expensive because it gums up the tooling even more than Aluminum does.

"Tim Williams" wrote in news:qdtvq8$gva$ snipped-for-privacy@dont-email.me:

He said "adhesive backed LED strips" So, if the LEDs exhibit heat and the designers of the strip knew that, the adhesive should be thin and one of the 'thermal' types. VHB sticks GREAT, but is usually pretty thick stuff, and I don't think it moves heat to well.

If he truly expects a heat issue, I would detach each LED from the strip and use thermal epoxy to attach them to a sinking mass.

as I expected, 6 to 1 half dozen to the other. the mask looks better so I'll just leave it. and may be a better bonding surface.

fact is, these strips do fine 24/7 without adhering to anything.

snipped-for-privacy@decadence.org wrote in news:qdu1j8$1lig$1 @gioia.aioe.org:

BTW, the 'air gap' I speak of is not in any way the interface between the LED and the sink. It is the elevated sink that allows air to pass under it I was referring to.

Heck, he could attach them to a Copper heat tube (readily available), and let that pull heat off the set.

Heat tubes are cool . I designed a charging device using a peltier array core and the heat tubes made the difference (because there needs to be a difference). It was one of my first 3D CAD layouts. Now I are a ME too. :-) (me and my CAD package)(wow).

Unless the copper area is heroically cooled (a zillion vias to a heat sink on the back side, or to an internal plane) the solder mask won't increase thermal resistance much.

Solder mask over solder coated copper tends to bunch up and crack. Solder mask over ENIG is fine.

But a solid rectangle of ENIG, gold, looks pretty good too.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

We've taken to using bare ENIG for our logo and board title. Bling bling!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

t in me.

but not grounded), as a base for a couple of those adhesive backed led stri ps that I mount on it. Had the boards done and there is solder mask coverin g those areas, which can be easily fixed but it may not matter at all. Just did the areas for any (tidbit) of added heat dissipation but probably best to let it go to straight plated copper area than a layer of solder mask in between?

id of it ?

!

5 colors; gold, bare fr4, soldermask over no copper, soldermask over copper , and white silk screen

fredag den 14. juni 2019 kl. 06.25.56 UTC+2 skrev John Larkin:

in me.

t not grounded), as a base for a couple of those adhesive backed led strips that I mount on it. Had the boards done and there is solder mask covering those areas, which can be easily fixed but it may not matter at all. Just d id the areas for any (tidbit) of added heat dissipation but probably best t o let it go to straight plated copper area than a layer of solder mask in b etween?

of it ?

ENIG is added after soldermask, so there is no gold under the soldermask

I guess not. When I scrape a trace to make contact, I do see copper. Well, the copper won't bunch up either.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

And the result is waaaayyy ugly. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

ist in me.

e but not grounded), as a base for a couple of those adhesive backed led st rips that I mount on it. Had the boards done and there is solder mask cover ing those areas, which can be easily fixed but it may not matter at all. Ju st did the areas for any (tidbit) of added heat dissipation but probably be st to let it go to straight plated copper area than a layer of solder mask in between?

rid of it ?

ing!

pper,

the result or the subject? ;)