Why so much silicone on electronic circuit?

[grizedale]

Hello,

We have a 2W xenon flash lamp in our product range.

It has a single sided PTH PCB.

The capacitors and inductors of the circuit are absolutely covered in silicone……..for the assembly staff there’s even a whole A4 page pointing out where the silicone should go.

Why have they used all this silicone.?

I was wondering if it is to provide support for the electrolytic capcitors and inductors, which actually hang upside down on the pcb, and being single sided, maybe they could simply peel off their pads and drop out if not glued in with the silicone.

Alternatively, maybe its to stop moisture getting near the connection points of the components to the pcb?

Alternatively, its because the tube trigger pulse is around 3KV and they want to stop this from arcing to metal bits of the components?

 

[tpetar]

To fix and prevent noise generated by this components, usually on lower frequencies. You can search edaboard threads there is threads with this thematic.

 

[grizedale]

oh so you mean audible noise?

 

[tpetar]

Yes this vibration can cause audio noise and cracking of soldering points and parts bodies, pins/connectors.

 

[grizedale]

-so my theories about the silicone........

...providing support
...stopping moisture ingress
...stopping high voltage discharge to component metal

.........are all worthless figments of my imagination?

[

 

[tpetar]

...add more weight to device :smile:
...add more bozons and atoms in circuit
......

I didnt think on that way but who knows everything is possible.... ;-)

If we fill complete device with silicone maybe we can make water proof device.

Inside almost all switching devices, you can find similar silicon glue around inductors and capacitors.

 

[grizedale]

OK , here goes,

tpetar it sounds like you are wanting to say what i am just about to say?....

Stuffing loads of silicone into electronic circuits is A COMPLETE WASTE OF TIME, but it makes the engineer that does it look like a real experienced guy, who knows all the tricks.

Is this true?

 

[sky_123]

I'm no expert on silicone, but maybe it is also being used as a form of insulator to stop arcing possibly?
I only say this because the few limited times I experimented with high voltage, I had to liberally coat
the board and leads with spray plastic, to stop it arcing (I was operating in the range of a few kV to maybe 10 kV,
and I had a compact board so I couldn't space things out).
Also, some designs where vibration is expected (due to the environment where they will be used - e.g. industrial/milspec)
tend to have tied-down components for things like large inductors and capacitors - maybe the silicone is for a similar
thing, to prevent the components vibrating off. Who knows : (

 

[tpetar]

OK , here goes,

tpetar it sounds like you are wanting to say what i am just about to say?....

Stuffing loads of silicone into electronic circuits is A COMPLETE WASTE OF TIME, but it makes the engineer that does it look like a real experienced guy, who knows all the tricks.

Is this true?

Its trick to prevent vibration of parts and making noise or some destruction of parts and boards. This is not only way to do this but its often used. I will post material about that.

- - - Updated - - -

Read this :

Magnetostriction
https://en.wikipedia.org/wiki/Magnetostriction

Magnetostriction (cf. electrostriction) is a property of ferromagnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of material's magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ.
This effect causes losses due to frictional heating in susceptible ferromagnetic cores. The effect is also responsible for the high pitch buzzing sound that can be heard near transformers on alternating current carrying pylons.

**broken link removed**

**broken link removed**

Transformer noise is caused by a phenomenon called magnetostriction. In very simple terms this means that if a piece of magnetic sheet steel is magnetized it will extend itself. When the magnetization is taken away. I goes back to its original condition. A transformer is magnetically excited by an alternating voltage and current so that it becomes extended and contracted twice during a full cycle of magnetization.

Of course, these extensions are only small dimensionally, and therefore cannot usually be seen by the naked eye. They are, however, sufficient to cause a vibration, and as a result noise.
The act of magnetization by applying a voltage to a transformer produces a flux, or magnetic lines of force in the core. The degree of flux will determine the amount of magnetostriction (extensions and contractions) and hence, the noise level.


Silicon glue or other strong epoxy glues fixes this parts inductors, capacitors to be strongly fixed and prevent them from vibrating and producing noise.


What to say, hardest problems often solved on simple way, with super glue, or like in SciFi movies when they saving world from some asteroids and equipment need to be fixed, and they use chewing gum to fix some parts and world is saved. :wink:

I hope that this post give new photons on this case.