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Subject:
From:
"Stadem, Richard D" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D
Date:
Tue, 31 Jul 2018 17:38:04 +0000
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text/plain (167 lines)
So you want to solder just 30 uinches of a gullwing connector lead frame to a number of OSP-coated bare copper PWB pads using lead free solder. Why only 30 uinches?
And the gull-wing SMT connector leads have 20 uinches of hard gold electroplated on them?
Why, sure you can! But it won't last very long. Sounds like a recipe for a perfect storm of issues.
You should pre-tin the connector lead-frame to remove the gold first. Why were they plated with so much gold? What is the base metal of the leadframe?
I would use an immersion silver plated PWB, not OSP.
I would also form the leads so you have more than 30 uinches of solder wetting to the pads/leads.
I would also qualify this process with some intensive reliability testing, including shock, stress testing for connector insertion, vibration and observe for fretting as well, and thermal cycling to failure.
All that may be overkill, but without a picture of the proposed leadframe, the board layout, the use environment, etc., it is hard to answer your question.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Tuesday, July 31, 2018 10:45 AM
To: [log in to unmask]
Subject: Re: [TN] Solder joint integrity

Dell - Internal Use - Confidential  

Fellow TechNetters:

   I did not get very many relies to my original inquiry.   Therefore I post a second time.

   Is it permissible to solder 30 micro inch of connector lead frame to PWB copper pad with Lead Free Solder.   What are the Pros & Cons.

Clarification statement:
   The PWB external copper pad finish is OSP.
   The M2 connector gull wing leads are plated with 20 micro inch of hard gold.
   The process solder is Lead Free.

   I have not seen a combination of this sort before.   SnPb and LF solder will solder to ENIG, Will a reliable LF solder joint be form with hard gold?

   Is there a reliability concern?????????

Victor,

-----Original Message-----
From: Giamis, Andy [mailto:[log in to unmask]] 
Sent: Friday, July 27, 2018 3:16 PM
To: Hernandez, Victor G
Subject: RE: Solder joint integrity

Thanks for the clarification.  That's totally different from what I was imagining.

I have also never seen Au plating on a gull wing lead, let alone hard Au.....

I have seen mezzanine card PCBs with edge pin connections.  The development products had full hard Au plating, eventually going to ENiG with selective hard Au on the contact fingers.  The development boards had regular SOICs, QFNs, BGAs and passive parts.  Essentially a similar situation, just reversed:  Soldered leaded components, one surface with thick hard Au.  This was several years ago and I don't have the hard data available to me anymore.  I remember that in reliability testing, leaded parts did well.  I think we had Au embrittlement on QFNs and some fine-pitch BGAs.  


How's your team down there in Austin?
I hope you got somebody good for that open position.

Best Regards,
Andy

Andrew C. Giamis
Senior Failure Analysis Engineer
CommScope
2601 Telecom Pkwy
Richardson, TX, 75082, USA
phone: 972-952-9847

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Friday, July 27, 2018 2:55 PM
To: Giamis, Andy <[log in to unmask]>
Cc: [log in to unmask]
Subject: RE: Solder joint integrity

Email Security Warning:

The following message was sent from an external e-mail address. Exercise caution when opening attachments, clicking links, or exchanging information.

Dell - Internal Use - Confidential  

Clarification statement:
   The PWB external copper pad finish is OSP.
   The connector gull wing leads are plated with 30 micro inch of hard gold.
   The process solder is Lead Free.

   I have not seen a combination of this sort before.   SnPb and LF solder will solder to ENIG, Will a reliable LF solder joint be form with hard gold?

   Is there a reliability concern?????????

Victor,

-----Original Message-----
From: Giamis, Andy [mailto:[log in to unmask]] 
Sent: Friday, July 27, 2018 2:41 PM
To: Hernandez, Victor G
Subject: RE: Solder joint integrity

I don't have any data to support a reliability assessment.  

The smallest I have ever seen for solder joints on connectors is in an I-Phone 4 tear-down I keep in the lab (see attached).

Maybe I don't understand you r intended application.
Just to confirm, you are soldering to a lead or post that has a solderable surface of 30 micro-inches?  That's about as thick as a hard gold plating.  
On this scale any Sn-based solder would just saturate with the PCB surface plating (ENiG, imAg or base Cu for OSP).  It would readily and completely form intermetallic.  You wouldn't have any solder left, just intermetallic.  I'd expect that this would crack on the first sneeze.

Best Regards,
Andy

Andrew C. Giamis
Senior Failure Analysis Engineer
CommScope
2601 Telecom Pkwy
Richardson, TX, 75082, USA
phone: 972-952-9847

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Friday, July 27, 2018 1:40 PM
To: Giamis, Andy <[log in to unmask]>
Cc: [log in to unmask]
Subject: RE: Solder joint integrity

Email Security Warning:

The following message was sent from an external e-mail address. Exercise caution when opening attachments, clicking links, or exchanging information.

Dell - Internal Use - Confidential  

Both, How Reliable is the solder joint given the working parameters.

-----Original Message-----
From: Giamis, Andy [mailto:[log in to unmask]] 
Sent: Friday, July 27, 2018 12:42 PM
To: Hernandez, Victor G
Subject: RE: Solder joint integrity

Hi Victor,

Is your primary concern soldering to 30 micro inches or soldering with Pb-free solder?

As long as the solder joints are well-formed, Pb-free solder shouldn't be an issue (SAC alloys and related).

30 uin of solderable surface on a leadframe sounds frighteningly small.    What kind of connector are you looking at?





Best Regards,
Andy

Andrew C. Giamis
Senior Failure Analysis Engineer
CommScope
2601 Telecom Pkwy
Richardson, TX, 75082, USA
phone: 972-952-9847

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Friday, July 27, 2018 12:27 PM
To: [log in to unmask]
Subject: [TN] Solder joint integrity

Email Security Warning:

The following message was sent from an external e-mail address. Exercise caution when opening attachments, clicking links, or exchanging information.

Fellow TechNetters:

   Is it permissible to solder 30 micro inch of connector lead frame to PWB copper pad with Lead Free Solder.   What are the Pros & Cons.

Victor,

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