What coating to use on PCB layers?

[glenjoy]

Can anyone suggest on what coating to use on PCB layers, I am in philippines so very limited resources here.

 

[flatulent]

Re: PCB Copper Coating

If it is not an RF type circuit, there are several commercial coatings which prevent fungus growth. These should be available to you in the same distribution channels as your electronic parts.

 

[glenjoy]

Re: PCB Copper Coating

Cool amp silver coating, is it good?

 

[House_Cat]

Re: PCB Copper Coating

You don't say why you want to coat the copper.

If you are trying to prevent atmospheric oxidation, solder mask will work. There are many types, and some are even fungicidal. Do a web search for solder mask. One source is:

hxxp://www.electronicplus.com/content/ProductPage.asp?maincat=cl&subcat=cs5

(x=t above)

You can also spray your assembled circuit board with acrylic or silicone lacquer as a protective conformal coating. These coatings even come in spray cans for low volume applications. The URL above also lists these coatings.

You mention "Cool-Amp" silver - this coating is expensive (about $140 US per pound). It is intended as an alternative to silver electroplating of mechanical contact surfaces on circuit boards. As a coating for a whole board surface, it has some problems. As with any silver coating, exposed surfaces will oxidize eventually into black silver oxide. Soldering requires careful cleaning of coated surfaces.

If you can be more specific about why you want to coat the board, perhaps you could get better suggestions.

 

[skywalker]

Re: PCB Copper Coating

glenjoy, do you need a
commercial coating, for example:
SnPb, HAL, Gold plated etc.

O you need a coating for home use ?
Skywalker.

 

[MCMC]

Re: PCB Copper Coating

Dear House_Cat

I very interested about this subject, is possible you explain about what method, products (solder mask) is used like a professionals PCB maker.

 

[House_Cat]

Re: PCB Copper Coating

I very interested about this subject, is possible you explain about what method, products (solder mask) is used like a professionals PCB maker.

There are books that cover the subject of each type of coating. It is too much to answer in a general way here. The following URL gives a brief outline of a few of the various solder mask methods. There are several others such as electrostatic deposition, etc.

http://www.parlex.com/dead/tech_papers/Flexible.htm

The other related subjects are conformal coatings and plating.

Conformal coatings are lacquers, epoxies, silicones, rubber compounds, plastic compounds, etc. They are used to cover and protect the assembled circuit board, or to cover and protect a specific portion of the board. Each method has its place depending on temperature, moisture, vibration, shock, etc. Again - there are so many that a general answer is not practical.

Plating is done to enhance mechanical contact, and/or to protect the surface of the copper from oxidation or abrasion. Plating metals include solder (HASL), tin (both electrolytic and electroless), gold (both electrolytic and electroless), silver (electrolytic and electroless), bonded metals, metalic ceramics, etc. Plating can be done over the entire board, or selectively just over contact fingers, pads, or specific areas.

What you need to do is define what you are trying to proctect against or enhance on the board - then you can get specific information about the recommended coatings or plating.

 

[MCMC]

Re: PCB Copper Coating

Hi House_Cat

Thanks for reply

I make my own pcb's in my home but I want it's looking like a professionals pcb.

 

[House_Cat]

Re: PCB Copper Coating

MCMC-

Home PCB makers can easily use inexpensive electroless tin plating to make a board look a bit more professional.

The tin plating chemicals come in powder for that is mixed with hot tap water. You have to carefully, and completely clean the bare board. Then you just soak the board in the solution according to manufacturers directions. "Tinnit" is one brand, and the below links show details.

h**p://www.web-tronics.com/er-18.html

h**p://www.minute-man.com/acatalog/Online_Catalog_PCB_Etch_Resist__Exposure_Kit__Etching_Solutions___245.html

 

[bomba]

Re: PCB Copper Coating

well, when I make a prototype PCB , I plate it using a solution based in silver cyanide.
:!: Is a toxic solution you must manipulate carefully. :!:
It consists of submerging the board in the solution by approximately 2 minutes, rinsing very well with water hot, and ready.

Be careful.

 

[spyghost]

PCB Copper Coating

all i use is plain acrylic paint... its cheap but it can protect the copper layer well. anyway its just for hobbyist type of circuits in my case.

 

[Santa]

Re: PCB Copper Coating

Here is my recepy for electroless tin plating of copper.

Please note that the tin is somewhat shiny and very solderable when fresh but will turn greyish and much less solderable with time.
So if you need to solder components (specially SMDs) later on the board,
it is advisable to put some true solder on the target pads to maintain long time solderability at these positions.
I also manipulate the boards with gloves at all times.

Electroless PCB Tin Plating
===========================

For 1000cc :

Mix 36ml HCl 12N and 3.8 gr SnCl2-2H2O in a pyrex beaker
Heat to about 80deg C and stir to solubilize as much as possible of the SnCl2.

Dissolve 49.5 gr of Thiourea in 964cc H2O at room temp in a beaker.

Pour slowly the first solution in the second one while agitating.

Add a few pearls of tin at the bottom of the solution, this will preserve it.

Protect the areas of the PCB that should not be treated with adhesive tape.

Brush perfectly the two copper sides with an abrasive rubber.
Do not touch the copper with the latex gloves, interpose a tissue paper between the glove and surface.

As soon as the surfaces are uniformly shiny and clean, dip the board into the solution held at 20-30 deg C.
Move slowly the board in the solution holding it with the gloves by the edges so that it does not touch the bottom or
the surface. Turn the board over every minute and leave it in the solution for 15 minutes or more.

Rinse very well with water and dry it.

When oxidized, to make the surface solderable again:

Scrub the surfaces with fine chalk powder and a piece of tissue. Clean the surfaces with a brush, water jet and free the holes with
a pin when chalk remains in them. Finish with a dip in diluted HCl and rinse in water. Dry at 50 deg C before soldering.

 

[sigint]

Re: PCB Copper Coating

Keep the tin solution far away from any copper plating bath - thiourea in very small quantities is a copper brightener ( very brittle and tarnishes quickly) but in large quantities - more than a few milligrams per liter it will make the copper plating bath useless.

SiGiNT

 

[daniyal]

Re: PCB Copper Coating

i want to COAT PVC with copper . the pvc is on cables and i want it to quote with copper for shielding pourpose. please some would like to tell me the product and the procedure.

tahnks

daniyal siddiqui

daniyalsidd@hotmail.com