Whatg is the cheapest and simplest 'finish' for a manufactured PCB?

[treez]

What is the cheapest, quickest-to-do, and simplest 'finish' to get put onto the pads of a PCB?....EG Lead free HASL, Leaded HASL, electroless nickel gold, etc etc ?

presumably the purpose of the 'finish' is to stop the copper of the exposed pads from oxidising?

 

[KlausST]

Hi,

HAL with or without Pb is good for long time storeage. This is because it is relatively thick and migrition is slow. But the thicknes and the variation in thickness may cause problems with high density BGAs.

Electroless nickel gokd is somehow the opposite of that. Thin, flat good for BGAs. But you should not store the boards more than some weeks before soldering.

Klaus

 

[candhg124]

The cheapest and quickest is HASL with lead or lead free.

What is the cheapest, quickest-to-do, and simplest 'finish' to get put onto the pads of a PCB?....EG Lead free HASL, Leaded HASL, electroless nickel gold, etc etc ?

presumably the purpose of the 'finish' is to stop the copper of the exposed pads from oxidising?

 

[marce]

Hi,

Electroless nickel gokd is somehow the opposite of that. Thin, flat good for BGAs. But you should not store the boards more than some weeks before soldering.

Klaus

Incorrect, ENIG has a shelf life of 12 months...
If you are using SMD components below 0805 and small pitch ICs below 0.127mm or any QFPs then HASL is not a good idea, it is not flat, has a meniscus and can cause assembly problems further down the line. The stencilling of solder paste and the volume of solder paste on an SMD pad is critical and incorrect paste or technique is the cause of 60% of reflow problems....the best and probably most widely used finish where reasonable shelf life, flatness and solderability is ENIG.
What you may save in board fabrication may well cost you a lot more during assembly.

 

[KlausST]

Hi,

@marce:
My "some weeks" are incorrect. According IPC-4552 ENIG should keep solderability for 6 month.

We are producing industrial measurement equipment. Without BGAs we use HAL down to 0603. No problems.
We have unsoldered HAL PCBs on stock because we produce very low volume.

With smaller devices or BGAs we use ENIG.

To go deeper in PCB finish there are a lot of technical documents in the www.


Klaus

 

[treez]

small pitch ICs below 0.127mm

thanks this is all good info, but I think you meant 1.27mm?

 

[Mattylad]

I too have used HASL for SMT, kept boards on the shelf (open shelf -not temp controlled etc) for several years and still been able to assemble them without problem.
If your manufacturer can produce the boards with a good level of flatness then they should be fine, I think a lot depends upon how good your manufacture is at it.

Mind you, roller tin has not been mentioned as the cheapest yet lol

 

[D.A.(Tony)Stewart]

What is the cheapest, quickest-to-do, and simplest 'finish' to get put onto the pads of a PCB?....EG Lead free HASL, Leaded HASL, electroless nickel gold, etc etc ?

presumably the purpose of the 'finish' is to stop the copper of the exposed pads from oxidising?

cheapest PWB's are FR-2 Phenolic paper with no solder mask using 1/2 oz Cu found in many consumer grade products.

the cost driver is usually not the coating, rather the copper total weight.

 

[marce]

How many products these days use Phenolic paper FR-2, not many world usage for Paper, CEM-1 CEM-3 is only about 5% of the worlds PCB production. Cost of FR4, SMD requirements means these type of PCBs are rarely used these days.

Source - World PCB production by Type of Substrate form the yearly IPC PCB World PCB Production document.

 

[candhg124]

the cost driver is usually not the coating, rather the copper total weight.

do not think so.
HASL and ENIG will be much different in the pricing.
Now 1oz and 1/2oz copper have no big difference. Of course, if more than 2oz, then it will be changing.