Led coatings

wietefras said:

Why? It doesn't really explain that the chart is after any effect? Or is that on a clean surface?

You might not "need"PU coating since the environment isn't that harsh, but if it's not losing 15% of the light it would seem a much better material for coating our leds. If we could pry off the original silicon coating that is.

Click to expand...

The chart shows that a 50 micron thickness of acrylic conformal coating,as also a 2mm thick silicone resin coating ,will not be as protective as a 2 mm thick PU resin coating .In contact with corrosive gases the LED device will lose about 20% of output ,not because of the light absorption by the coating ,but by the tarnishing that
the corrosive environment will cause to the internal reflector of the LED device.

Light absorption is greater in the case of silicone and PU coatings ,as both have a thickness of 2 mm,whereas the
acrylic coating is 40 times thinner.

Acrylic conformal coating is the best DIY option available ,in many aspects
( price,ease of application,curing,protection,light output losses and CCT shift,etc).
At least for our purpose ,of protecting the LEDs operating in the average environment of the artificial horticulture.

Rocket Soul said:

My buddies TEKNIK didnt like the acrylic too much, he said he had problems with it loosening. He said it worked ok on nichias but not great with his seul semiconductors.

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Was he using the Plastik 70 or the
Plastik 70 Super ?

Plastik 70 has a max operational temp of 60C ,while Plastik 70 Super has a
max operational temp of 125 C.
Exceeding the max oper. temp. can
cause the deterioration of the conformal coating ,which most probably will start to peel off .
Especially on the spots where it has
covered the silicone phosphor encapsulation of the LED devices.

SDS_GR said:

Was he using the Plastik 70 or the
Plastik 70 Super ?

Plastik 70 has a max operational temp of 60C ,while Plastik 70 Super has a
max operational temp of 125 C.
Exceeding the max oper. temp. can
cause the deterioration of the conformal coating ,which most probably will start to peel off .
Especially on the spots where it has
covered the silicone phosphor encapsulation of the LED devices.

Click to expand...

The only one I can find in my area without ordering a case from overseas is this:
MG Chemicals Acrylic Lacquer Conformal Coating, 340g (12 Oz) Aerosol Can, Clear https://www.amazon.ca/dp/B008OA7178/ref=cm_sw_r_cp_api_i_xFK1EbW48P7AY

canope said:

The only one I can find in my area without ordering a case from overseas is this:
MG Chemicals Acrylic Lacquer Conformal Coating, 340g (12 Oz) Aerosol Can, Clear https://www.amazon.ca/dp/B008OA7178/ref=cm_sw_r_cp_api_i_xFK1EbW48P7AY

Click to expand...

It will do !
More info :

SDS_GR said:

Light absorption is greater in the case of silicone and PU coatings ,as both have a thickness of 2 mm,whereas the
acrylic coating is 40 times thinner.

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Ah ok, because in this test the coating is 2mm thick it absorbs so much light.

But the leds we buy are already covered by a protective silicone coating. Which is much thinner.

Still, I would not like to put any coating on top of the silicone coating.

wietefras said:

But the leds we buy are already covered by a protective silicone coating. Which is much thinner.

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Not exactly (if I’ve understood you correctly ) ...

The phosphor conversion LEDs have a silicone phosphor encapsulant ,but
it is gas permeable .Silicone is chosen
because of it’s high thermal stability ,as it is in direct contact with the LED chip .

Monochromatic LEDs have a crystal
clear “dome” acting as lens.
Also made from gas permeable silicone.

So,actually the silicone phosphor encapsulants and the silicone domes of
most high quality LEDs offer no real protection against moisture and gasses like oxygen ,H2S or SOx
that oxidise the internal reflector of
the LEDs.

Either the LEDs have to be enclosed
in an air tight case (which actually is not such a good idea )
or
a conformal coating has to be applied.

Then the only factor that can affect directly the operating efficiency and service life of LEDs is their
junction temperature.

No, I'm saying that the leds are already coated with silicone. Which is not a material you can easily "paint" over. So I would not choose to put any layer on top of them. Especially after reading earlier in the thread that someone had the issue of the coating coming loose.

"Conformal coating" is only one way of dealing with this though. There are many techniques of coating leds. Although I guess if you feel like spraying something on top of the leds DIY then it would be your only option left.

I’m not aware of this silicone coating over LEDs.Can you elaborate a bit more?
Any links for further info on this ?

SDS_GR said:

I’m not aware of this silicone coating over LEDs.Can you elaborate a bit more?
Any links for further info on this ?

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He's talking about the silicon lens. But he hasn't read the article properly and doesn't realise the graph on the first page refers to flux characteristics AFTER exposure to corrosive gases such as sulfur dioxide. It is not a guide to flux characteristics of the different conformal coatings in general. Fluence (Osram) uses a silicon conformal coating on its LEDs, as do others, and there is probably a reason for their preference over acrylic.

Any proof that indeed Fluence and/or others use silicone conformal coatings ?
I had the impression that professionals opt always for the parylene conformal
coating (applied by chemical vapour deposition).

Furthermore ,in order for the silicone resin
to be an effective conformal coating ,
it has to form a film which is at least 40-50 times thicker than the effective
thickness of the acrylic conformal coating .As it becomes quite obvious ,
silicone conformal coatings absorb much more light from the source,thus
the output power losses are far larger than other coatings like acrylic or parylene.
That fact alone would rule out silicone as a conformal coating for
LED horticultural lighting ,where high efficiency is an attribute so much sought after in the art and trade ...

SDS_GR said:

Any proof that indeed Fluence uses silicone conformal coating ?
I had the impression that professionals opt always for the parylene conformal
coating (applied by chemical vapour deposition).

Furthermore ,in order for the silicone resin
to be an effective conformal coating ,
it has to form a film which is at least 40-50 times thicker than the effective
thickness of the acrylic conformal coating .As it becomes quite obvious ,
silicone conformal coatings absorb much more light from the source,thus
the output power losses are far larger than other coatings like acrylic or parylene.
That fact alone would rule out silicone as a conformal coating for
LED horticultural lighting ,where high efficiency is an attribute so much sought after in the art and trade ...

Click to expand...

Think I saw an Irish youtube spiderfarmer SF1000 review where the coating was peeling back and appeared floppy. I made the assumption that it was silicone-based off that. We all know where ass comes from.

BTW,
here’s a nice read ....

Method and device for producing a parylene coating

Current Assignee Osram Opto Semiconductors GmbH

• BACKGROUND
• [0003]
  Corrosive gases such as, for example, sulphur compounds lead to corrosion of sensitive surfaces of electrical components, for example, in the case of optoelectronic components. Thus, silver surfaces, for example, of optoelectronic components can corrode as a result of such gases and thus lead to the failure of the components.
• [0004]
  There are furthermore applications that necessitate the use of silicone as an encapsulant for surrounding an electrical component such as, for example, an optoelectronic component. Silicones, however, typically have a more or less high permeability to corrosive gases. A modification of silicones, for example, an increased incorporation of phenyl groups, can indeed lower permeability. However, even such modified silicones offer no adequate long-term stability against corrosion.
• [0005]
  Although use of other materials such as, for example, gold instead of easily corroding materials such as, for example, silver, increases stability to corrosion, it is often not possible for reasons of cost.
• [0006]
  A material that has a high barrier property and thus a low permeability to corrosive gases is, for example, parylene, which, however, is customarily only applied by vacuum or low-pressure methods. For mass production of electronic components such as, for example, optoelectronic components, known parylene coating methods are therefore unsuitable as the components must be coated in a closed volume and a controlled vacuum or low pressure. This either leads to very long production times or alternatively, in the case of ribbon coating methods, to an economically high technical and financial outlay with regard to the coating plants.
• [0007]
  It could therefore be helpful to a method for producing a parylene coating on at least one surface of at least one component. It could further be helpful to provide a device for carrying out such a method.

Osram makes LED devices which
have their internal silver reflector coated with Parylene.

Cheers !

is anyone here using a coating on their strip builds? Has anyone here suffered damages from humidity?
I’m in the middle of a build and even before this thread I was considering applying something to the bare leds.
looks like some of these coatings have a service life below that of the leds which is concerning.

I ‘ve used many times isopropyl alcohol to clean the LES of my Vero 29 & Citizen COBs,as also to clean the tiny domes of Osram Oslons,from dust and debris,without the slightest issue.

I’ve used also isopropyl alcohol to
remove acrylic conformal coatings from the DIY electronic pcbs of mine.

I think you got the picture .
Easy to remove the old coating and re-apply a fresh one ...
More than a few reasons why the acrylic conformal coating is a true friend with the bold DIYer ...

And BTW,
it’s quite difficult to notice the damage on LEDs from moisture .
Unless you regularly inspect every each one of the LEDs with a welder’s mask /glasses ,when the lights are switched ON.

SDS_GR said:

I’m not aware of this silicone coating over LEDs.

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Eh, what? You even said it yourself.

Just read a datasheet for LB301B and search for silicon. Or a Citizen COB. Especially the blue COB where they only have a silicone cover over the blue led (with no flourescents).

SDS_GR said:

conformal coatings ...

Click to expand...

You keep saying "conformal coatings" like it means something special. All it means is that it's applied over the entire surface and not just the LES. Another option is a "dispensing coating". Same material, same effect, just another method of applying the coating.

wietefras said:

Eh, what? You even said it yourself.

Just read a datasheet for LB301B and search for silicon. Or a Citizen COB. Especially the blue COB where they only have a silicone cover over the blue led (with no flourescents).

You keep saying "conformal coatings" like it means something special. All it means is that it's applied over the entire surface and not just the LES. Another option is a "dispensing coating". Same material, same effect, just another method of applying the coating.

Click to expand...

Actually is as special as it can get ...
Not the same materials & not the same effect .
I think you have misunderstood quite a few things.

Conformal means that it conforms to every contour of a 3D shape.

Dispensing is an application method,
like dipping,brushing,spraying ,etc.

And the LES or dome lens of any LED is NOT a protective coating.
They do not protect the internal parts of a LED , like the die itself or the reflector of the die ,from environmental hazards.

SDS_GR said:

I think you have misunderstood quite a few things.

Click to expand...

A protective coating can also be applied by dispensing. It's does not have to be spread all over the board.

Anyway, like Teknik already concluded, you should not be putting protective coatings on a silicone base

Everyone has the right to draw their own conclusions .
Maybe that Teknik gentleman discovered( and by now he is already aware of ) something that Cree,Bridgelux,Nichia,Citizen,Osram,
Samsung and others haven’t discovered yet and are completely unaware of ..

SDS_GR said:

More about Parylene

Click to expand...

I like that magazine. Gives an interesting insight into the industry, or what the industry wants me to read.