Encapsulants?

LEDBE
C

CPF Dude

Newly Enlightened
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Jul 31, 2010
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Hi all,

Wondering if someone can point me to info on encapsulants -- what types exist, and what I should use. I want to make a custom LED display with special shapes on it. Sort of like making my own bargraph display or light bars. I would use a PCB and some SMD LEDs, then a plastic housing over it, but I need to fill the holes in the plastic housing with some filler material (encapsulant?) that would diffuse the light at the top of the housing, so it's nice and even. Clear filler material would probably not be ideal, but something milky-ish. However it would have to not be too milky as it would attenuate the light output.

Any info, pointers, etc? BTW, making the PCB with SMD LEDs and the plastic housing I can do already, so it's just that filler I need to investigate.

Thanks,
-Neil.
 
So you want something like the rubber button ins a TV remote?

if they are custom shapes, cast some silicone

or any plastic that is semi-opaque really, even a thin layer of paint on clear surface will give you the effect
----------
Project to check out that may help you:

"making my own bargraph display" = check out Stribe
also your general description is simmilar to = monome/bliptronic/bliptronome
 
Last edited:
There's a lot of stuff out there. I'm not sure if encapsulant is the right term, or maybe it's just a type of potting, etc. I've worked with potting in various electronics designs, and have a few manufacturers bookmarked. Maybe this will be a starting point:

http://www.masterbond.com/

loctite - their website is really user-hostile lately. Don't know why. They make a range of pottings and encapsulants for auto electronics use. The website that I can reach is:
http://www.henkelna.com/cps/rde/xch...________0000000389|pageIndex=0|action=search|

(I wonder if that'll work as a link?)

Emerson & Cumings made/make a lot of good pottings. Unfortunately, they are owned by Henkel, who also owns Loctite, and the website is also messed up.

Dow Corning: they make all sorts of chemical products.
http://www.dowcorning.com/applicati...N=0&bhcp=1&DCCD=PRODUCT&WT.svl=1&DCCT=PRODUCT
Maybe an electronics grade RTV is good enough?

shoot... that's all I've got. I'm not sure what the best option is, but this will certainly educate you on some of the stuff that's out there.

regards,
Steve K.
 
Something more like this... http://ledtronics.com/products/ProductsDetails.aspx?WP=C91K162 , except instead of the rectangles for each segment, I would have different shapes.

I've found companies that make various chemicals for this, but not sure what I need, and which to use. I'm trying to educate myself before I contact those companies, and I'll need a source that sells very small quantities. I'm hoping that some compound used for something else (like silicone, epoxy, etc) may work well.

Thanks.
 
Pretty sure they're not, but whatever they are, I want to make my own custom-shaped version. Or let's say I want to make my own light bar, like this, but with my own shape and size ...
MU03-2201.jpg
 
Steve K said:
aren't those just standard rectangular leds, overmolded with white plastic?

Steve K.
Click to expand...

Yep that's what they are... only difference from the standard LED bargraph listed below it is the fact the it's in a semi circle and they have all their cathodes tied together...

You might be able to emulate that design with different 5mm LEDs and some black epoxy and a mold of some sort? Would be messy I'm guessing though?
 
What I want is custom shapes for which I can't get standard LEDs. Back to the topic at hand -- anyone know of some resource that explains the different types of encapsulants that exist and the pros/cons of each?
 
I just got a reply from the Henkel rep.... she gave me a link that provides an overview of their rather large selection of products:

http://electronicscatalogs.henkel.com

Page 15 discusses products for the LED lighting market. There are a few products mentioned for encapsulants. One is the Hysol Stycast NX76:
https://tds.us.henkel.com//NA/UT/HNAUTTDS.nsf/web/55C8E8E7CAA25A2685257589006EEB8C/$File/STYCAST%20NX-76-EN.pdf

Technology Epoxy
Appearance Opaque white
Components One-component
Product Benefits • One component
Cure Heat Cure
Application Encapsulant

The phrase "opaque white" doesn't sound like a good match if you want something transparent or translucent.

The Stycast 2017M4 seems better suited:
https://tds.us.henkel.com//NA/UT/HNAUTTDS.nsf/web/851E591B7CBD3FB285257589006E6032/$File/STYCAST%202017M4-EN.pdf

Appearance
(Component A)
Clear blue
Appearance
(Component B)
Clear
Components Two component - requires mixing
Mix Ratio, by weight -
Resin : Hardener
100 : 100
Product Benefits • Two component
Cure Heat Cure
Application Encapsulant
Typical Assembly
Applications
LED's
STYCAST 2017M4 is an epoxy encapsulant developed for blue
Light Emitting Diodes.

Doesn't say if it is clear (or bluish clear) when it is cured though...

The brochure does have a page that appears to cover plastic used to overmold small circuit boards. Maybe that would be the type of product that is appropriate?

The rest of the brochure is pretty interesting to browse. Products for conductive adhesives, thermal adhesives, special solders, conformal coatings, potting materials, etc. Very useful stuff if you deal with electronics packaging for a living.

Generally, if there are questions about the products, I'll call the company. They have applications engineers that can guide me to the correct product. Of course, they also want to know how much of the stuff I expect to use every year too.

regards,
Steve K.
 
..and silicone will get a bit milky with time..

just in case you want the silicone to be, and stay, water-clear for a long time, use Lexel. much more expensive than regular silicone though, and thinner, so it fills better, and self-levels if necessary.
 
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