Led coatings

Some LED makers put a plastic coating over the LEDs, is there an aftermarket solution to DIY? Is it even a good idea?

Plastic coating? Only two things really come to mind here, those screw on LED bulbs with the plastic diffuser or phosphor free LED with a phosphor diffuser, but maybe I'm not hearing you right.

SPLFreak808 said:

Plastic coating? Only two things really come to mind here, those screw on LED bulbs with the plastic diffuser or phosphor free LED with a phosphor diffuser, but maybe I'm not hearing you right.

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Some have a plastic film over the board/strip

You might be talking about conformal coating, I use polyurethane CC with circuit boards but I'm not sure exactly what the LED companies use, probably silicone based. All this does is add a layer of protection from moisture.

It’s actually called conformal coating.
There are few different types of it,depending on the coating material used,like Parylene,acrylic,polyurethane,silicone and more .

Many of them can be found in spray can format .
Electrolube AFA is one of them ,
very well suited for LED applications.

SDS_GR said:

It’s actually called conformal coating.
There are few different types of it,depending on the coating material used,like Parylene,acrylic,polyurethane,silicone and more .

Many of them can be found in spray can format .
Electrolube AFA is one of them ,
very well suited for LED applications.

Digikey will be selling the new Samsung Horticulture Linear LED strips.

Too much of blue output in relation to the red one. Maybe even not enough green output ,when at high densities ( > 800 mol/sec/m^2) . An unbalanced “burple” with a hint of green & yellow . The R&D department behind this Sammy horti-strip ,for sure did not have cannabis in mind . 3000•K 80Ra...

www.rollitup.org

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Awesome stuff, do you know if you lose alot of umol?

If the coating is applied properly and forms a thin layer of about 30um thickness , then the output loss is negligible.

SDS_GR said:

If the coating is applied properly and forms a thin layer of about 30um thickness , then the output loss is negligible.

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Good stuff man, thanks for the insight will visit Akzo Nobel tomorrow and ask them what they have to offer. Will update

SDS_GR said:

If the coating is applied properly and forms a thin layer of about 30um thickness , then the output loss is negligible.

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in your opinion is acrylic better than silicon?

Yes,I think that acrylic is better than silicone.
Silicone coat has to be very thick to be protective enough .
Furthermore ,acrylic is much more transparent and colourless ,than silicone .
And won't yellow under UV radiation .
Here you can read a quite informative article about conformal coatings and their application to LED devices .


Edit :
Some more info on conformal coatings and their application at LED devices .

Read carefully when this condition stands ...



FIG. 6. Different coating types can suffer varying degradation in optical efficiency when exposed to corrosive gases.



Environmental exposure
Comparing the performance of various products in harsh environments can also highlight preferential product choice based on the end-use conditions. For example, Fig. 6 illustrates the effect of corrosive gas environments on an acrylic conformal coating, a polyurethane resin, and a silicone resin by examining the percentage reduction in luminous flux of the LED after exposure to a mixed-gas environment. These results clearly illustrate the importance of choosing the correct product for the environment. Although the conformal coating does not deteriorate in terms of its surface insulation resistance in a corrosive gas environment, it is not an adequate protection for LEDs as it allows the gas to pass through the thin coating and penetrate the LED, thus degrading its performance over time.
A similar effect is also seen with the silicone resin; however, in this case, despite the protection layer being considerably thicker (2 mm versus 50 μm) the gas is still able to pass through the resin and affect the LED. When you compare the result of the silicone resin to the polyurethane material, it is evident that there is a difference in performance exhibited by these two chemistry types as the silicone resin is permeable to the gas whereas the polyurethane resin, at the same thickness, is not. In such cases, an optically clear polyurethane resin, such as Electrolube UR5634, would be the most suitable protection media to prevent the corrosive gases from adversely affecting the LED.



Such environments will not occur in an artificial horticulture facility of any size ( from a server tower case to a vast greenhouse ) ,under normal circumstances .
PU coatings are used in really harsh enviroments ( metal /petrol /gas industries ,mining ,etc ) and
are quite thick ( 0.5 to 2.5 mm ).

Here some types that Cree suggests :


Source : https://www.cree.com/led-components/media/documents/XLamp_Chemical_Comp.pdf


Parylene aside ,all others (I think ... )can be applied at home ,with various methods .

And here are some common ( to EU countries ) conformal coatings :

(acrylic,solventless )

(acrylic,solvent-based)


( Caution : Plastik 70 SUPER and not the Plastik 70 which has a max oper. temp. of 60°C ) ( acrylic ,solvent based )


( polyvinyl butyral -solvent based )

SPLFreak808 said:

All this does is add a layer of protection from moisture.

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.....
“This elastic & transparent conformal coating ,as long as is applied and cured properly ,will protect the LEDs from :
-humidity, but also from water splashes ,sprays & mist.
- various hazardous to LEDs gasses ( like oxygen ,H2S , SOx ) and atmospheric pollution.
- dust ,fibers and other airborne solid particles .
- UV radiation
- VOCs
and from few other hazards that may
develop on an unprotected pcb ,even like “tin whiskers”.

They also protect you and others from
high voltage ,if present .“.....

SDS_GR said:

.....
“This elastic & transparent conformal coating ,as long as is applied and cured properly ,will protect the LEDs from :
-humidity, but also from water splashes ,sprays & mist.
- various hazardous to LEDs gasses ( like oxygen ,H2S , SOx ) and atmospheric pollution.
- dust ,fibers and other airborne solid particles .
- UV radiation
- VOCs
and from few other hazards that may
develop on an unprotected pcb ,even like “tin whiskers”.

They also protect you and others from
high voltage ,if present .“.....

Click to expand...

Exactly, and moisture lowers your output after a while

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.

SDS_GR said:

.....
“This elastic & transparent conformal coating ,as long as is applied and cured properly ,will protect the LEDs from :
-humidity, but also from water splashes ,sprays & mist.
- various hazardous to LEDs gasses ( like oxygen ,H2S , SOx ) and atmospheric pollution.
- dust ,fibers and other airborne solid particles .
- UV radiation
- VOCs
and from few other hazards that may
develop on an unprotected pcb ,even like “tin whiskers”.

They also protect you and others from
high voltage ,if present .“.....

https://www.tandfonline.com/doi/full/10.1080/09506608.2019.1565716?scroll=top&needAccess=true#

https://cdn.samsung.com/led/file/resource/2019/06/Application_Note_Guides_on_Chemical_Compatibility_Rev.0.2.pdf

https://www.vossloh-schwabe.com/fileadmin/user_upload/Chemical_Incompatibility_EN.pdf

https://www.bridgelux.com/sites/default/files/resource_media/AN51_revA%20Chemical%20Compatibility%20of%20Bridgelux%20SMD%20Products.pdf

https://www.nichia.co.jp/specification/products/led/ApplicationNote_SE-AP00012C-E.pdf

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I actually didn't even think of dust/particles etc, Excess build up of dust can be conductive, some environments more than others.

Temperature range another one to consider, with daily use you don't want to sit at boarderline temps with your conformal coating.

SDS_GR said:

Read carefully when this condition stands ...

Click to expand...

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.