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June 2012

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From:
Robert Kondner <[log in to unmask]>
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Date:
Thu, 28 Jun 2012 20:44:00 -0400
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Karen,

 Great paper, thank you. 

  Not a large change for simple SMT paste flux residues but I can see issues
if the entire board, or section, is covered with the flux.

Thanks,
Bob K.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Karen Tellefsen
Sent: Wednesday, June 27, 2012 7:25 PM
To: [log in to unmask]
Subject: Re: [TN] High frequency, ENIG and no-clean

Sort of.

We  saw a shift in the resonance frequency for T-resonators with and without
no-clean solder paste flux residues.  Relating this to dielectric constant
is not easy for the reasons given by Frank

M. Duffy et al,  RF Characterisation of no-clean solder flux residues
International symposium on microelectronics, Baltimore MD ,
2001  , vol. 4587, pp. 138-143

Karen Tellefsen - Electrical Testing
Alpha / 109 Corporate Blvd./ S. Plainfield, NJ 07080 [log in to unmask]
908-791-3069




From:   Robert Kondner <[log in to unmask]>
To:     <[log in to unmask]>, 
Date:   06/27/2012 03:06 PM
Subject:        Re: [TN] High frequency, ENIG and no-clean
Sent by:        TechNet <[log in to unmask]>



Frank,

 I was happy to hear your personal attitude towards No Clean, but I was
hoping for something a little more analytical.

 You mention the coating can and does act like a dielectric, but what value?
Is it close to FR4? Air? If someone takes a network analyzer can they detect
the presence of a glob of no clean left on a joint? I don't know, I am
simply asking.

 The high Z application you mention where a no clean residue affected
performance, that is not a RF and dielectric issue, that is a conductivity
issue.

 It is these "Soft and Fuzzy" personal observations that really don't count
in my book. Like Joe Friday: "Just the Facts Ma'ma". Anything else is, well,
potential hogwash. 

Thanks,
Bob K.



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Frank Kimmey
Sent: Wednesday, June 27, 2012 2:06 PM
To: [log in to unmask]
Subject: Re: [TN] High frequency, ENIG and no-clean

Okay Bob, let's discuss what happens with no-clean and RF.
No-clean leaves residue, commonly contaminants are contained in an inert
(after cure) material.
This coating can and does act as a dielectric.
As we know, dielectric changes impedance and impedance is what RF is all
about.
Now, where the real issue comes to play is that the residue left by no-clean
is not a consistent thickness and dielectric thickness is what has the
largest effect on RF impedance.
So if no-clean causes impedance changes/mismatch in some areas of the RF
path and not others then performance is adversely affected.
My first experience 20 years ago with this phenomenon was with high
impedance analog terraces were we saw a marked degradation in performance of
analog sensor circuits due to no-clean.
Now with higher powered RF circuits we see that any time loss is critical
(the key here is loss not power so it doesn't really matter how large the
signal is) no-clean does bad things to our signals.
Some of us use ENIG in our RF designs (I like the noble metal if I need to
leave exposed), others like IAg (silver is a great conductor) and others use
ISn (Tin works if you don't mind a whisker risk).
Bottom line is for best performance you need consistency and with no-clean
you don't get it as the left overs are not consistent across the circuit and
that DOES cause signal degradation.
At least that's what I have observed.
FNK


Frank N Kimmey CID+
Manager - PCB Design
Powerwave Technologies Inc.
Mobile - 916-670-0645

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Wednesday, June 27, 2012 10:37 AM
To: [log in to unmask]
Subject: Re: [TN] High frequency, ENIG and no-clean

Richard,

 I absolutely believe the ENIG issue is important. It was the No Clean part
of the question I was wondering about.

Bob K.

PS: I am about to hit send! :-)

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, June 27, 2012 1:25 PM
To: [log in to unmask]
Subject: Re: [TN] High frequency, ENIG and no-clean

Sorry about that, "send" button was hit before I finished.
Ioan's original question was:
Can anybody point me towards papers talking about the influence of no-clean
soldering and ENIG on high frequency performance?

- With ENIG, your final surface layer is nickel, not gold.
- For very high frequency signals (generally considered to be above 1
gigahertz), electrical conductance takes place on the surface of the trace
(the nickel-plated part) due to the Hall or "skin" effect. 
- Nickel's conductivity at frequencies above 1 Ghz is somewhat reduced,
compared with copper or gold. This is considered a "lossy" circuit
performance. There are many papers on this subject, including some from
Werner Engelmaier.
- I did not address losses through flux residues, only those regarding
signal loss in Db through nickel. But again, signal crosstalk and loss
through flux residue is well-documented. 

I can assure you, Bob, it is NOT "hogwash".


-----Original Message-----
From: Stadem, Richard D. 
Sent: Wednesday, June 27, 2012 12:10 PM
To: [log in to unmask]
Subject: RE: [TN] High frequency, ENIG and no-clean

Go back to Ioan's original question:


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Wednesday, June 27, 2012 11:46 AM
To: [log in to unmask]
Subject: Re: [TN] High frequency, ENIG and no-clean

Hi,

 I have often wondered if this No-Clean Flux vs. RF issue was real or hog
wash so I tried to look at these links.

 The first link must have changed pages, can anyone identify the new link or
subject description.

 The second link was about the Ni plating vs. RF.  I saw no reference to
flux or no clean. Did I miss something in my quick scan?

Thanks,
Bob K.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, June 27, 2012 11:31 AM
To: [log in to unmask]
Subject: Re: [TN] High frequency, ENIG and no-clean

http://www.taconic-add.com/mwg-internal/de5fs23hu73ds/progress?id=rG3E1oaXW1


http://athena-gatech.org/papers/staiculescu13.pdf

There are many more.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Wednesday, June 27, 2012 9:00 AM
To: [log in to unmask]
Subject: [TN] High frequency, ENIG and no-clean

Dear Technos,

 

Can anybody point me towards papers talking about the influence of no-clean
soldering and ENIG on high frequency performance?

 

Thanks,

 

Ioan Tempea

Ingénieur principal de fabrication / Senior Manufacturing Engineer

  <http://www.digico.cc/> 

 

950 RUE BERGAR, LAVAL, QC, H7L 5A1 <http://g.co/maps/2gh3f> 

T+ 1 (450) 967-7100, EXT244

------------------------------------------------------------------------

    <http://www.facebook.com/pages/Digico/277076778479> 

------------------------------------------------------------------------

Lauréat Dunamis 2012 <http://digico.cc/dunamis-2012/> 

Entreprise manufacturière / Gestion du capital humain

 


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