PCB surface finish. HASL .. ENIG .. Immersion Silver .. etc

[ahmedadelhosni]

Hello all,

One of my friends told me that when he orders from pcbcart.com he choose the surface finish to be Immersion Silver. See here. That option adds solder paste on top of the pads and with only hot air the components are soldered easily at once.

Is this option included in dirtypcb ?
There are only HASL and ENIG which I didn't understand there definitions when I googled them.

This link for example explains it all but I can't find any word related to solder paste.

Thanks.

[scalz]

@ahmedadelhosni
I'm not expert at all..I have only used hasl and enig. I have stenciled only hasl for the moment, and had no problem with fine 0.5 pitch too.
To be honest, I use mostly hasl (often for proto). But I think, imho, ENIG is better than HASL for outdoor or harsh environment application (outdoor climate, cars...) and durability of the device pcb (but I still would add some coating in case... ). For indoor, i think HASL/FREE is enough for me. I use HASL just for price concern lol.
I don't know well other finition..but about solderpaste, what I like is, it stick the component when you put it on pcb...but I should try once Immersion silver, your friend has an interesting idea. Still noob on this
I looked at pcbcart...seems expensive, even for hasl, isn'it???

[ahmedadelhosni]

@scalz Thanks for the info. Yes the minimum options on pcbcart are more expensive than dirtypcbs. But actually the quality is really great and impressive.

[bjacobse]

Well think in which environment and usage. for most personel use HASL is good enough. And my note is you can always spray Plastic 70, which is epoxy all over your finished soldered PCB, (Cover connectors) Then you have a quite good protection of your PCB in harsh environments
https://www.google.dk/search?q=plastic+70

https://en.wikipedia.org/wiki/Electroless_nickel_immersion_gold
https://en.wikipedia.org/wiki/Hot_air_solder_leveling

Experts comments: http://www.circuitnet.com/experts/86232.html

[ahmedadelhosni]

@bjacobse Thanks for the links.
You have any idea whether the immesrion silver put a layer of solder paster like my friend told me ?

[bjacobse]

Silver is cheaper than gold
http://www.multicircuits.com/pcb/tech/surface_finishes.html

So I would belieive the best is ENIG (Gold) then Silver immersion, then HASL.
But again, if you for your own project "quickly" solder your PCB after receiving it, HASL is the one for you.

Silver have shelf life up to approx 1 year
ENIG "kind of forever" shelf life (but depends of humidiy fo the shelf)

[ahmedadelhosni]

@bjacobse Thanks for the answer. I still have two questions please.

How did my friend tell me that immersive silver doesn't not need extra solder ? He told me that it comes with solder paste on it and just by putting the components and heating , then it will be soldered.
Is this true ? Is this with ENIG ? or only immersive silver ?

I didn't get what you mean by "shelf life up" ? Can you rexplain further in more details.

Thanks for your help.

[bjacobse]

@ahmedadelhosni
I have no idea what your friends tell you - you must ask him to explain the details. Since I makes no logic what he have told you
Shelf life - is the time from when you get the your "stuff" to you actually are using it. Ie. you receive a PCB and pout it to your shelf for a time, and then one day you decide to take it from your shelf and actually want to solder components on it.
The thing with metals is that the oxidate /corrode . if it's not easy yo understand with PCB and pads that corrode and makes soldering impossible. Then think of normal iron on your car. when exposed without paint it starts corrode, and noone can actually weld on corrosion, they must first grind/sandpapaer corrosion away down to bare iron, and then welding is possible - it's analogy to PCB and soldering pads and components

[ahmedadelhosni]

@bjacobse Clear enough and detailed. Thanks very much for your help.