The green stuff on a PCB

[The Master]

Hi. I have a few questions about the green stuff that goes on the underside of a PCB over the tracks.

First of all whats it called?

Is it possible to put it on a home made PCB?

[duncan303]

Hi

the green stuff is referred to as Soldermask.


Is it possible to put it on a home made PCB?

it is possible there are various products, but if you are not wave soldering(essentially dipping the whole board in molten solder) it could depend on the reason you wish to apply a coating as there could be something better.

Duncan

[mackrackit]

I always thought the green stuff was mold :)

If you are just wanting to seal the board from corrosion when it is finished, a can of clear spray paint works well. Clear finger nail polish for small jobs or touch ups.

[The Master]

wow, you guys replay fast on here.

I want to apply it because of corrosion, making soldering easier (the solder wont run down the track like it does when its bare) and it prevent things accidentally touching tracks (things include screwdrivers, metal filings, wires and fingers :P)

I would like to apply it before soldering because making soldering easier is one of the reasons i want to do it. The problem i see is how do i keep the pads clear?

Clear spray paint sounds like a good idea.

I have some stuff called "PCB Laquer" i think. Someone gave it to me a while ago and siad it was something to do with protecting PCBs but ive never used it. Is that anything similar?

[Luciano]

Hi,

I use that:

http://www.crcind.com/wwwcrc/tds/TKC3%20FLUXSK10/css/TKC3%20FLUXSK10.htm


http://www.crcind.com/csp/web/ProdDisp.csp?lng=3&country=ALL&product=FLUX%20SK%2010&brand=KOC&CSPCHD=00000001000741eqndXG003674297023

CRC Industries UK Ltd
Ambersil House
Wylds Road
Castlefield Industrial Estate
GB-BRIDGWATER. SOMERSET TA6 4DD
ENGLAND
Phone : +44 1278 727200
E-mail Address : [email protected]

* * *

Best regards,

Luciano

[mister_e]

When i do some home-made PCB, i use Liquid Tin (MG Chemical 421-500ml)

And then i solder my components on, clean the board with Isopropyl alcohol to remove flux, and that's it.

You can still apply some clear varnish on if you want. Clear spray would do the job.

[duncan303]

No hanging about here!

well fair enough you have listed all the advantages of a soldermask, except cosmetic so that makes it easier.
ruffling about in her handbag you could end up with any colour nail varnish :D

cheap and cheerfull you could leave the bare copper untinned and let it oxidise for a few days, then get a standard pencil rubber and clean just your annular rings and pads etc. if you do not add extra flux you will find that the oxidation acts as a sort of mask, then when you have finished populating use your acrylic laquer to spray the whole PCB.

it sounds also a bit like you may be overdoing it with the solder if it has decided to run off down the tracks :), try getting in the samllest guage solder you can. also do you have enough heat in your iron tip and are you using lead free?

I should be able to remember what you could use to speed up the oxidation, would hydrogen peroxide on some cotton wool placed in a sealed jar with the board do it? or is it sliced potatoes?

There are some "conformal coatings" that allow you to rework I think electrolube do one but I am not sure.

Are you mounting SMD's? one trick I have used that may help is to tidyup using thin solder braid that can leave tidy pads especially in a very restricted area and due to extreamly small pitches.

Don't know if this is helping so I will stop

Duncan

[mackrackit]

wow, you guys replay fast on here.
I am at work...so I am keeping busy :)


I have some stuff called "PCB Laquer" i think. Someone gave it to me a while ago and siad it was something to do with protecting PCBs but ive never used it. Is that anything similar?
Same idea. Me, I like to "tin" the boards first, makes surface mounts easier. Then some scotch tape across the pads before I spray paint (if I paint first). Then when the board is tested and ready to go I will spray the whole thing again. I have gotten to these maybe extremes because most of my stuff ends up in very high corrosion places.

I do a lot of one time stuff, so I do not very often use an outside service to make the really nice boards. Takes some time though to make a board that will last.

I think sparkfun.com has an article about solder masking.

[duncan303]

Hi Luciano

I have some of the SK10 I found it really sticky as if it never properly dried out, it worked well as a flux and to protect against oxidation but it just kept attracting dust.

I can remember having a hell of a time getting it off, the only product that seemed to work effectivly was Chemtronics Flux-Off.

Duncan

[The Master]

So this laquer stuff. Did i understand correctly that it works as both a protective layer and soldering flux so i could spray it over the whole board and solder ontop of it? (something like that anyway)

Whats an SMD? Probably not because i dont know what they are.

How do you "tin" a board and what is scotch tape?

I have 2 soldering irons. the old one is the best although the tip is about a sharp as a balloon and the new one (brand new!) doesnt appear to heat up enough to melt the solder properly so i dont use that so often. I dont know if my solder is lead free (ill have to check when i get home)

Just having a look on SparkFun.com now to see if i can find that article

Edit: If any of these questions have already been answered then i didnt understand it

[mister_e]

So this laquer stuff. Did i understand correctly that it works as both a protective layer and soldering flux so i could spray it over the whole board and solder ontop of it? (something like that anyway)
Protective layer only. You want to spray your board at the end unless you will smell the burned varnish all the time.. not a good idea.


Whats an SMD? Probably not because i dont know what they are.
Surface Mount Device. they came in various flavors.
http://en.wikipedia.org/wiki/Surface-mount_technology


How do you "tin" a board and what is scotch tape?
There's several way, i use the Liquid Tin i suggested above. Once your PCB is done, you just drop it in the liquid for ~1 minutes... then you clean it with hot water and let it dry for few minutes... then you solder your parts on.

Or you can use your iron, apply solder on all tracks, then remove the "excess" (not sure of the translation... sorry) with solder wick (desoldering braid). What's desoldering braid? http://www.mgchemicals.com/products/braid.html

Scotch tape... something like that
http://solutions.3m.com/3MContentRetrievalAPI/BlobServlet?locale=en_US&univid=1114305207819&fallback=true&assetType=MMM_Image&blobAttribute=ImageFile&placeId=7BC6E48B1800BAE180A88EBDDE34901D&version=current

[mackrackit]

Laquer is not a flux. Can not solder through it.

SMD= surface mount device

Scotch tape= generic for the clear tape that you might use on a package (birthday, Christmas)

I tin a board by fluxing the traces and melting a very little bit of solder on before I place the part. The are other ways though.

Dull iron, get a file .

[mister_e]

:eek:

Dull iron, get a file .
Get a tip instead ;) unless the soldering process is not going to work really good. IMHO.

[duncan303]

So this laquer stuff. Did i understand correctly that it works as both a protective layer and soldering flux so i could spray it over the whole board and solder ontop of it? (something like that anyway)

The SK10 to which I was refering to is NOT the same as the laqur that you might have.


Your product could probably be sourced from Maplin:
PCB Lacquer
• Fast drying acrylic coating
• Acid and alkali resistant
• Multi application
• Seals printed circuitry
• Use for over-lacquering of metal and paintwork
• Ideal as a waterproof coating for maps and technical documents
• Supplied in a 200ml can

Is this the same product it would say Maplin on it?

It is a bit of a nightmare as there are more "service aids" stuff in aerosols and bottles than one man can reasonably want or use.




The tinning I use is
Seno Immerse Tin 90g for 1ltr £11.50 from megauk, mix it yourself as it has a short useable life in weeks, It is extreamly poisonous, not really to be chucked down the drain! as with almost anything to do with PCB production these days.


Whooaa this thread is sure am moving :D

Duncan

[mackrackit]

:eek:

Get a tip instead ;) unless the soldering process is not going to work really good. IMHO.
Just seeing if anyone would comment on that :) File as a last resort!!

[The Master]

I will check out the laquer when i get home. I cant remember where its from.

So, i cant put normal laquer on the PCB before soldering. Is it fine to do it if somehow it doesn touch any of the pads?

Ive always been told never to file a soldering iron because it wont work properly. Something about the heat not being focused to the point or something. Ive not seen anywhere that sels the kind of tips the old one uses. I could do with a new really expensive one from Rapid that will work well.

If you cant put it down the drain then where does it go?

I dont have any Surface Mount Devices but i do put components on the underside of the PCB to save space sometimes



I tin a board by fluxing the traces and melting a very little bit of solder on before I place the part. The are other ways though.


Traces? Should that have been "tracks"? Do you mean you flux the whole thing but only put a bit of solder on the pad or do you put solder on the whole thing too?

[The Master]

I cant find that article on that site but i did have fun reading some other articles they have.

Ive just had a random idea that might work :P What if i took a laminating pouch and cut holes in it to line up with the pads on my PCB then ran the PCB and the pouch through a laminating machine?

[mackrackit]

So, i cant put normal laquer on the PCB before soldering. Is it fine to do it if somehow it doesn touch any of the pads?
You can do it before soldering if you keep it away from the pads. Just as well to do it when you are finished, like misterE said, it will smell


Ive always been told never to file a soldering iron because it wont work properly. Something about the heat not being focused to the point or something. Ive not seen anywhere that sels the kind of tips the old one uses. I could do with a new really expensive one from Rapid that will work well.
If you are careful you can get away with filing. You will need to "tin" the iron afterwards. The main problem with filing is some of the tips are only copper coated, if the tip is solid copper you will be fine. File in the shape of "V", not a long point like a needle.



Traces? Should that have been "tracks"? Do you mean you flux the whole thing but only put a bit of solder on the pad or do you put solder on the whole thing too?
Traces , tracks . All the same for me.
Sometimes I only tin the pads and sometimes I tin the whole thing. Solder will not corrode as fast a copper. So it all depends on the job.

There is sometimes a problem with tinning, but you can have that problem no matter what because you have to use solder. That problem is the dreaded "Tin Whisker". But I think sealing the board after all is finished will help to stop the whiskers. Maybe skimask will chime in on that subject.

[duncan303]

Get a tip instead unless the soldering process is not going to work really good. IMHO.

This could be a big subject about tips etc, personally I never touch my tips with anything other than solder, I used to wipe them on a pad using pure water from the reverse osmosis kit, but I do not even do that now I only use Weller wool balls.

Tips are pretty expensive. anything I can do to extend thier life is worthwhile.

working on say an 0402 series without a decent iron is a total non starter.

However making sure that the tip is in "proper thermal contact" with the heating element is a daily good housekeeping task, even an oxidation layer can make a differrence, I do use several tips during a session so try I to make sure even little bits of grit get in.


Just the thought of somebody coming anywhere near my tips with a rasp file is well and truly an :eek:

Duncan

[The Master]

I use wet tissue to clean my tips. Im not sure if thats right or not but its what we were taught at school so probably not.

0402 series? Are they the SMDs again? Ive never actually soldered any of those but i did manage to wrap wires around all 3 pins of and SMD transistor once

[Luciano]

Hi Luciano

I have some of the SK10 I found it really sticky as if it never properly dried out, it worked well as a flux and to protect against oxidation but it just kept attracting dust.
I can remember having a hell of a time getting it off, the only product that seemed to work effectivly was Chemtronics Flux-Off.

Duncan

Hi Duncan,

After I apply the spray SK10 on the PCB, I bake the PCB for about 10 minutes in a preheated
pizza oven at about 100°C. After this treatment, the SK10 film on the PCB is dry.

Best regards,

Luciano

[duncan303]

If you cant put it down the drain then where does it go?

Topical subject:)

Bit of a cop out for me to be totally honest. I collect all suspect waste and it goes into a single container, I keep an eye on it if I am adding something new, which is kept cool and out of sunlight, and when I remember I take it to the assemblers, the company who do the board population.
I assume it goes in with their industrial waste (but I have not checked too hard).

I do sometimes wonder if they just take it to humour me and just turn round later and chuck it down the sink!

I have sometimes added it to old engine oil and taken it to the recycling centre but the addition is not miscible, but at least I know it will be properly processed. I suppose I would rather get caught adding it to oil rather than chuck it down the drain. If I could threw it far
enough it would end up in the North Sea. Wonder what PPM dilution that would be, probably have to start using moles.

Trouble is once the idea of having to deal with the waste is planted in ones head, it becomes a serious problem. (which is why I shared it, you know what they say...)

Anyway if anybody from the authorities (if there is anybody, which I very much doubt) reading this reply then......................


you ain't seen me right!


.

[mackrackit]

Just the thought of somebody coming anywhere near my tips with a rasp file is well and truly an :eek:

Duncan

I can understand that, but look at it this way. Someone had to grind, file, rasp, or use a small lathe to make the tip in the first place. I have an old iron that has the hard to find tips too. A friend of mine makes them for me. I am not sure of the alloy, it is a hard copper of some kind. When he is finished shaping and threading I clean the tip and drop it in a lead pot to tin. Works good. But that is just me.

[duncan303]

Luciano


After I apply the spray SK10 on the PCB, I bake the PCB for about 10 minutes in a preheated
pizza oven at about 100°C. After this treatment, the SK10 film on the PCB is dry.

I remember now, I thoughtlessly used the domestic cooker once, never again!!!!!

I went out and bought a small pizza style oven instead; that I was intending to convert into a reflow but the heat was neither uniform or hot enough to be usefull. also the tray was too small to be of use on that project, so it ended up back in the kitchen as a cheese/sardines on toast oven, oh well... so you win some you.......

That also reminds me that I also went back to sparkfun today, not only because of the earlier post but also because about the same time as the oven debacle, I was attempting reflow in a large frying pan inspired by sparkfun. Hasn't he come a long way, looks like he may be making a few bob, good on him.

[skimask]

I collect all suspect waste and it goes into a single container, I keep an eye on it if I am adding something new, which is kept cool and out of sunlight, and when I remember I take it to the assemblers, the company who do the board population.
I've got a metal container that gets all of the little solder bits, wires, basically anything that gets touched by the lead in the solder. When that container gets full-ish, I take it down to the local radiator repair shop and put it in with their 'industrial waste'. They've got all sorts of signs up in the shop saying they're 'HAZMAT' compliant and all that, so I figured it's got a be a decent spot. And since my stuff is such a small quantity, they don't mind at all.
Where it goes after that? I have no idea. But I figure with all those signs, and the way things are going these days, they have to be doing something halfway right or they'd be out of business right? I work in a shop at the base that does circuit card repair work, I could take the waste material there, which would also be a misuse of gov't resources (did anyone else see that article about gov't employees charging up gov't credit cards lately?)...besides, it's only 6 miles to the radiator shop, 27 miles to the shop on base.
Same thing goes with the little brushes and cotton swabs I use to clean off the boards. I put them in a closed container. When it gets about half full, I leave it outside in the open air for a days or so to dry everything out, then put that material in with the solder waste. The guys at the HAZMAT shop on base say it's a decent method of handling stuff.
Hey...at least I'm trying...
Oh, and that radiator shop also has an oil burner for a furnace, burns oil at something like a billion degrees, they take used motor oil too. They've also got an antifreeze recycler...3 for 1 deal for me...

[duncan303]

Hi Dave,

Sorry I wasn't thinking with my practical hat on, I was just being anally retentive about my precious little tips :D

if I cross contaminate the tips even with lead<>leadfree they simply will not "wet" properly I am probably doing something really wrong, maybe time to look at a hot air rework station they seem to be very popular. Although I just know that if I breathe on a 0402 I will never see it again :) Its getting to the point where I can't see them anymore I just hope I know where they are!!

Duncan

[duncan303]

Hi Skimask


oil burner for a furnace, burns oil at something like a billion degrees, they take used motor oil too.

OMG :eek: I assumed my oil was being reprocessed recycled. How typically stupid. I can be so niave sometimes!

anyway I am glad that I am not alone in some of my more bizarre habits of waste sorting.


You lot over there are generaly a couple of years ahead of us, we (europeans) are just starting to deal with recycling but only through threats of massive fines and thats our governement being fined by some foreigner called Brussells!.

So our local authorities are running around like headless chickens, literally.

I referbed a old A3 printing heat press that had fluffy asbestos in it, so I phoned up the local council to ask them where I dispose of it, a few hours later and many transfers, I was eventually informed that there was "NO" facility available to members of the public in the county to dispose of it. They were terrified, no joke. I've still got it.

I air out the aromatic organic solvents as much for my own sanity as for the environment:)

[skimask]

I assumed my oil was being reprocessed recycled. How typically stupid. I can be so niave sometimes!
I'm not even 100% sure that burning it at high temp's is good enough. Think of all the metallic contamination that's probably in there (especially if it came from a worn out motor). The guys at the HAZMAT shop said the costs involved with actually recycling oil are way too high, and you basically end up with the same problems anyways.


You lot over there are generaly a couple of years ahead of us, we (europeans) are just starting to deal with recycling but only through threats of massive fines and thats our governement being fined by some foreigner called Brussells!.
I don't know about that. The gov't still hasn't switched over to lb-free soldering practices yet. In fact, it was only touched on in that micro-mini-circuit card repair class I went to last year. And if you look at all of the boards coming out of SE Asia these days, practically every one of them has lb-free markings on them.


I air out the aromatic organic solvents as much for my own sanity as for the environment:)
And again, as far as the HAZMAT guys are concerned, most commercially available products these days can be aired out without much worry. The main concern was the ozone depleting stuff (freon, etc). Good luck finding any of that these days.

As far as the cross-contamination goes...In the shop, I've got 2 sets of stations, one set for lb-full and one set for lb-free. If I get any lb contamination on the lb-free tools, those parts go over to the lb-full station. So basically, when I need to buy stuff, I buy it for the lb-free work, and move it over when I screw up :)
And, the instructors at that school said if you get lead into a lb-free environment, things get all screwy. You end up having to pump a load of heat into the product to get it to do anything for you...and by that time, you probably end up melting the PCB :)

[The Master]

Im back home now. I cant find the laquer stuff. I know its here somewhere but with the state of this place at the moment i doubt ill find it soon. I do have my solder to hand though. Its "Lead free solder. Composition: SN 99.3% CU 0.7% 1mm diameter"

[mackrackit]

Hi Duncan,
I was not thinking about Pb free stuff. I am still a 60/40 type :eek: But Pb is the least of my worries. At my day job, one of my duties is heading up our HAZWOPER team. That stands for Hazardous Waste Operations and Emergency Response. Mostly the emergency response part.

As far as your waste disposal goes, sounds like you are "OK".

One thing I have heard about waste oil, and I do not know if it is true. It gets hauled to the cost and loaded on a ship. Once past the twelve mile limit a valve is turned. Now it is a fuel.

[Archangel]

Hi Duncan,


One thing I have heard about waste oil, and I do not know if it is true. It gets hauled to the cost and loaded on a ship. Once past the twelve mile limit a valve is turned. Now it is a fuel.
That is what the recycler told me too . .

[duncan303]

Hi Dave


One thing I have heard about waste oil, and I do not know if it is true. It gets hauled to the cost and loaded on a ship. Once past the twelve mile limit a valve is turned. Now it is a fuel.

AAAArggghh. Just goes to show what a massive problem it is for all of us..

My 5 Gall drum is about 1/2 full, but there are some empty 100gal barrels I could start using. Not a solution I know. maybe I am making matters worse by combining, I should look at the COSH sheets and see if I can grade the waste and maybe I should deal with the tin plating separately.

Hi Skimask

if you get lead into a lb-free environment, things get all screwy

We eventually had ROHS April last, and such a build up.... every other conference or article was about it. Now you hear practically nothing!

How did it impact me, well I tried to get my BOM lists done early at least 12 months, by the Date I only had one component NON-ROHS( subsequently designed out), which I thought was pretty damn good, it was helped by good support by suppliers, one of the first to make it easier was Farnell who is Newark for you, they seemed to be the first to allow a set global search preference of ROHS only, and then introduced "good" alternative suggestions to all search results.

Vishay amongst others caused a big problem with all its rebranding nonsense and nobody knew either where the datasheets were or verified ROHS or not, that was the biggest problem really, finding reliable alternatives.

I have sub assemblies come in from Shenzen, hands up I admit it (no choice), and they could'nt have left it closer to the mark. And I got left with a RoHS unverified order :(, cheers guys, hope the games go well.

I use digi-key and they have had the RoHS combo box for a long time, no doubt they will start to offer more services as the date approaches.

Having said all that, the transition appears to have been pretty smooth, still a lot of tight lipping to some subjects, a sort of wait and see policy. Who is going to get prosecuted first and exactly what for. To *******ise a quote from this forum "if anybody is actually going to appear at the door armed with anything more than a digital fridge thermometer........"

So it really comes down to two areas manufacturing vs hobby, as long as you do not place a particular product "on the market", you can do pretty much as you please, therefore all prep DFM work can be as hazardous as you wish, but you cannot sell (or in my opinion give) anything non compliant to any other person.
So making a nice enticing hobby non-rohs led flashing christmas decoration that a little baby is going to want to put in its mouthand suck, seems to still be fine.
Perhaps they should adopt the same policy for heroin addicts and just let them have as much heroin as they want, when they want, as long as the do not give it away or sell it, Big problem solved!

On the bench, lead free soldering has all its associated difficulties, at first there was no alternative. Brussels left it up to manufacturers and market demand to provide a lead free solder that people could actually use so loads and loads of test samples became available as giveaways, and it all became great copy in the periodicals. For me I have piles of samples enough to keep me going probably for years, I tend to choose any one that has the highest silver content, purely personal. But improved "solderability" is gradually being addressed in other areas, pcbs come back gold HSL etc. so by the time you have to set up to the plate things could be a little easier.

I still cannot sculpt lead-free as well as leaded (rosin and colophony free) so I may use leaded for amendment prototyping, lead-free is so fragile especially when you are adding unsupported components and the board is getting a lot of handling. Same as you Skimask any contaminated tips get relegated.

One thing I do on production boards which I haven’t seen anywhere is pre clean a length of solder with isoprop and then only handle and feed with lint free glove, my other glove is an unpowdered latex.

In the service and repair industry for goods previously on the market I recall it as being like for like, how much that is adhered to is anybodies guess, what still is unresolved is that if I want to use say a TDA series and sell it as part of an in-car product it is NON-RoHS, otherwise it is RoHS.

Generally Medical, Military and Motor are exempt. I can understand nobody really taking much notice if the tomahawk approaching you has been verified RoHS, but I do wonder about spending an hour or so inside a hot NMR scanner. Of course the motor manufacturers are exempt because……….err mmmmm….

cos we all need to err……?

Duncan

[skimask]

pre clean a length of solder with isoprop and then only handle and feed with lint free glove, my other glove is an unpowdered latex.
Exactly what they taught us in that school. You can clean the heck out of a board, clean the parts, perfect tips, and so on. Then a guy comes along and grabs that solder wire with his greasy hands and ruins everything. While I don't go as far as you do with the gloves, I do wipe down the last few inches of solder with iso before I use it.


Generally Medical, Military and Motor are exempt.
For that matter, on some things it seems like they're exempt from using solid state components...Tubes all of the place! Although I know the root reasons of why some boxes still use tubes. EMP comes to mind for one thing...

[duncan303]

Hi Duncan,
One thing I have heard about waste oil, and I do not know if it is true. It gets hauled to the cost and loaded on a ship. Once past the twelve mile limit a valve is turned. Now it is a fuel.

have had a reply



Dear Duncan

Thank you for your query regarding engine oil recycling. I have also
received a telephone message. Apologies for the delay in reply, I have
been away on leave.

Used engine oil is collected from all of our 19 recycling centres by a
company called Malary Oils.

Most oil recycling companies use a similar process. Once the oil is
collected it is taken for testing. Dependant on it's quality some of it
will be sent for disposal (which will either be incineration or a
hazardous landfill site) and the rest can then be reprocessed. During a
slow heating process water is separated from the oil. The water then
goes to a water treatment facility. The oil is then filtered and acts as
fuel for high temperature combustion furnaces and boilers.

I hope that this information is of use. Please do not hesitate to
contact me should you have any further enquires.

Regards,



Not too bad a reply, suppose its landfill vs international waters then.

I think I might delve further and see if the criteria for incineration/landfill is degree of contamination.



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