Since our first use of ENIG I have not seen or heard of an issue with black pads. Keep in mind that for some boards if we make 200 pieces we have made a lot.
From: Inge Hernefjord [mailto:[log in to unmask]]
Sent: Thursday, September 15, 2011 5:28 PM
To: TechNet E-Mail Forum; Phil Nutting
Subject: Re: [TN] ENIG versus LFHASL
no RF... and no bananas ...
the bad reputation of ENIG, does it not belong to history now? I used to get ENIG issues on my desk once a week, but have not heard of any problems for years. Probable cause is that they buy lots and that there is a stringent quality/process control, not only in a bunch of papers, but in the daily routines. Our purchaser or the component guy knows that he can't sit in his chair all day, but got to visit the board maker frequently. A ticket to Shanghai or Tokyo or like costs less than a handful of PWBs. Don't tell me that your company is a small one, then the reason for personal contacts is even more worthful. Standing still one week can be catastrophic for a small entrepeneur with only one source and only one product, while a mega one can redirigate to another plant in the country or abroad.
I've heard that american electronic engineers in general are little slow when it comes to 'benchmarking' , but I do not know if it's true.
//Inge
On 15 September 2011 22:40, Phil Nutting <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Ok, so we use SMT and PTH circuit boards, all are low speed (20 kHz to 50 kHz), no BGAs, smallest parts are typically 0603, no Bluetooth, no RF, typically 0.015 pitch. Environment might be a medical office, airport, semiconductor fab or research lab.
As for all the geniuses getting together to decide... I'm it. There is no one else that has in depth knowledge of all the possible factors. I guess I could go out to lunch and discuss it with myself over a couple of martinis. Yum!
Phil
-----Original Message-----
From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On Behalf Of Stadem, Richard D.
Sent: Thursday, September 15, 2011 3:19 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [TN] ENIG versus LFHASL
Regarding my previous post, I am not saying anyone should not use ENIG. You just need to be knowledgeable in ALL surface finishes before you make a selection.
Surface finish is not something you pull out of your hat based just on whether the CCA is going to be lead-free, although that is definitely one of the factors.
For example, you need to consider the type of circuitry. If it is an analog, high RF, Bluetooth CCA for example, ENIG would be your last choice (it may be too lossy, and if you do not understand what that means you should not be determining the surface finish alone).
If it is a double sided SMT CCA with BGAs on both sides, with through-hole parts that require hand soldering, and must be processed using lead-free solder, why then, ENIG might just be the best choice. Or it might not. In that case, OSP is definitely not the best choice.
Selection of finish should be left to a team of engineers who know all of the advantages/disadvantages of each finish and understands (intimately) his/her particular circuit design types (RF receiver/converter, digital processor card, power supply card, D/A card, thermoswitch device, etc,) and there are many to consider. The designer, process engineer, and quality engineer should also be familiar with the fabrication capabilities (or conversely, the weaknesses) of the different fabricators they have a business relationship with, and have that in mind when selecting a finish also.
It is definitely NOT something a manufacturing engineer alone should decide based solely on process type or "personal favorite".
-----Original Message-----
From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On Behalf Of Stadem, Richard D.
Sent: Thursday, September 15, 2011 1:37 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [TN] ENIG versus LFHASL
In fact, Werner wrote entire papers about the possible problems with using ENIG. Here are some; http://content.yudu.com/Library/A1qwqg/GlobalSMTampPackagin/resources/61.htm
http://www.trafalgar2.com/documents/Issue_Archive/global_7.3_us_opt.pdf
-----Original Message-----
From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On Behalf Of Reuven Rokah
Sent: Thursday, September 15, 2011 1:19 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [TN] ENIG versus LFHASL
I am in favor of LFHASL because of its robust in processes and storage conditions. You just have to choose the right alloy in the HASL process.
You can search in the IPC archive and read Werner recommendations, he was favor of Immersion Silver and against ENIG because of the Ni3Sn4 IMC layer, High thermal energy (15 degC) at reflow soldering, lnferior electrical properties of solder joints and other reasons such solder d black pads.
Reuven
On Thu, Sep 15, 2011 at 8:00 PM, Phil Nutting <[log in to unmask]<mailto:[log in to unmask]>>wrote:
> Hello Technetters,
>
> We are having a discussion about the merits of both ENIG and LFHASL.
> In
> 2006 when we switch to a RoHS compliant process we evaluated many
> board finishes and decided, for our volumes, that although ENIG was
> more expensive it was more robust. LFHASL wasn't ready for prime
> time, Immersion Silver was great but required careful storage and
> handling, OSP was not something that fit our process.
>
> Now that LFHASL appears to be more main stream we are reconsidering it.
> ENIG is not always done in-house at some of our fab shops, so that
> adds time and money to the delivery. These shops now have LFHASL
> in-house, so there is a potential for some savings here. We have been
> given stories of storage issues with LFHASL and other concerns too.
>
> As I recall, the industry recommended method of storage of bare
> circuit boards is in a sealed bag with desiccant, regardless of board finish.
> Leaving bare boards unwrapped and in an open bin is just plain bad
> practice especially if near the ocean.
>
> Several of us here think LFHASL is now right for our processes.
>
> Please advise if we are off base.
>
> Phil Nutting
> Design for Manufacturing Engineer
> Kaiser Systems, Inc.
> 126 Sohier Road
> Beverly, MA 01915
> Phone: 978-922-9300 x1310<tel:978-922-9300%20x1310>
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> e-mail: [log in to unmask]<mailto:[log in to unmask]><mailto:[log in to unmask]<mailto:[log in to unmask]>>
> www.kaisersystems.com<http://www.kaisersystems.com/><http://www.kaisersystems.com<http://www.kaisersystems.com/>>
> www.linkedin.com/in/philnutting<http://www.linkedin.com/in/philnutting><http://www.linkedin.com/in/philnutting
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>
>
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