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PbF PCB finish

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asir

#46940

PbF PCB finish | 23 January, 2007

Can some of you kindly share some of your experiences with PbF PCB finish (OSP, ENIG, Immer Sn, Immer Ni,etc.) What are the benefit and disadvantage? Some of the issues that has been encountered.

Which one you would recommend?

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#46951

PbF PCB finish | 24 January, 2007

Immersion Silver, ImAg, is becoming the finish of preference. This is due to it having similar process limits vs. SnPb HASL. There were some early concerns about shelf life, but new chemistries have extended finish shelf life to 12 months+. Many board vendors outsource this process ( another possible risk ) so make sure you ask all the right questions up front.

Some of my opinions on other finishes:

OSP : Bad for ICT bed of nails probing. Gums up the works, affects yields directly.

ENIG : Still has a bad rep for black pad.

Immersion Sn : Not enough info available on Sn Whiskers and overall long life reliability

Immersion Ni : No opinion, have not seen much info on this

Also : Pb Free HASL is coming and looks promising. I need to see more data on this if anyone has info NOT connected to any vendor promo info.

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RDR

#46952

PbF PCB finish | 24 January, 2007

immersion silver has become my favorite finish for lead free. Seems toi have good shelf life is stored in the silversaver paper. and reflows real well.

Russ

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#46957

PbF PCB finish | 24 January, 2007

We have been using SN100C lead free hasl for over a year now with good success. It is very solderable and has good shelf life. You do have to make sure the finish gets applied to the correct thickness. If the lead free hasl finish is not applied thick enough the intermetallic layer will be exposed and the PCB will not be solderable at all. We encountered problems related to the hasl finish being applied too thin when we used a PCB house that sent our boards out of house for lead free hasl finish so make sure you choose a PCB house with their own lead free hasl line that has the ability to measure the thickness of the coating. The manufacturer of the lead free hasl solder material recommends 100 micro inches minimum thickness we spec 120 micro inches minimum thickness.

We have also used quite a bit of Immersion Silver and have not had any issues yet. It solders very well. We really have not had anything sit around long enough to know if shelf life will be an issue yet. I really like how flat it is.

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greg york

#46980

PbF PCB finish | 25 January, 2007

Strange as we have had huge problems with Silver in Many different Assembly houses. Mainly with Nitric Acid based Silvers causing blow holes, non wetting and even the Nitric etching away the tracks on fine boards. It has been one of the main problem areas for us. OSP not Rosin Lacquer is good had no issue's. Remembering that you now have high Tin to wet to the Copper so is better than Leaded. Lead Free HASL is a hassle due to improper processing and reliability concerns. Ni/Au going well Cheers Greg

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Derek W

#47171

PbF PCB finish | 2 February, 2007

We've had the same issues with silver. We also ran into shelf life issues but that's specific to our business. We've moved to ENIG with good success, our board vendors were also very happy to move away from silver though I'm not sure why.

As long as the board shop has good controls in place black pad does not seem to be an issue.

The only unusual thing we're finding is that ENIG wets a little slower in the wave machine which we found supprising because the finish wets so well at surface mount with lead free.

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greg york

#47195

PbF PCB finish | 4 February, 2007

The wetting problem is strange, is the metal in the pot a golden/yellow colour? what temp are you running the pot at? cheers greg

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CL

#47197

PbF PCB finish | 5 February, 2007

ASIR,

Findings for us so far:

OSP- has worked well for us for single sided boards only. We have seen problems with using it on double sided reflow applications. Also, some customers have specified OSP, but are intolerant of exposed copper. Limited shelf life Silver- Seems to work well. Have had some vendor quality problems from the board houses. If double sided, secand reflow must be ASAP as silver begins to tarnish almost immediately after first reflow. Storage conditions are critical. Tin- We have had nothing but problems with tin. Short shelf life. ENIG- My preferred plating. Wets well, good shelf life, So far we have not had any problems with black pad (although having said that, I am expecting to)

Good Luck

Chris

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