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May 2000

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Subject:
From:
"Wenger, George M (George)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 9 May 2000 17:59:07 -0400
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text/plain (96 lines)
Tri,
Bob Furrow is correct.  You need to remember the XRF doesn't measure
thickness.  In essence, the proportional detector measures atomic mass and
the instrument is ususally calibrated with known thickness materials so that
the results can be related to thickness.  You can dip a copper sample into
SnPb solder and blow off all of the solder leaving only the copper-tin
intermetallic (Cu3Sn or Cu6Sn5) and when measured with an XRF calibarted to
measure solder thickness will indicated that there is some solder present
(0-40 microinches) and that it will have a high tin composition (70-100%).
If you cross section the sample you'll more than likely find that there is
only intermetallic left on the copper.

-----Original Message-----
From: Furrow, Robert Gordon (Bob) 
Sent: Tuesday, May 09, 2000 7:15 AM
To: [log in to unmask]
Subject: Re: [TN] HASL Tin-Lead component in thin coating


Tri,

I assume you are using X-Ray fluorescence to determine thickness and alloy
composition. When you measure a thin pad (under 1 um), you are also picking
up the tin from the CuSn intermetallic layer which is tin rich. The thinner
the HASL coating, the higher the tin content expected since the
intermetallic thickness relative to the bulk HASL coating is increased.

Thanks,
Robert Furrow
SMT Process Engineer
Lucent Technologies
978-960-3224    [log in to unmask] <mailto:[log in to unmask]> 


        -----Original Message-----
        From:   Le Dai Tri [SMTP:[log in to unmask]]
        Sent:   Tuesday, May 09, 2000 4:16 AM
        To:     [log in to unmask]
        Subject:        [TN] HASL Tin-Lead component in thin coating

        TechNeter,
         
        We use horizontal HASL machine. When I measured the thickness of
tin/lead 
            if the thickness was over 1um, the component of tin was 64~69%, 
            if the thickness was under 1um (0.8~0.9um), the component of tin
was always over 70%. 
            (Tin/lead made-up in solder pot was 63+/-3%; 37+/-3%; board
thicness was 1.6mm)
        I did'nt know the reason why? 
         
        In the case of component of tin was over 70%, what will happen in 
        PCB Assembly manufacturing?
         
        Any help would be appreciated.
         
        Best regards,
        Tri'.
         
        _______________________________________
        PWB Development
section                                                             
        E-Mail    :  <mailto:[log in to unmask]>
[log in to unmask]                                                
  
	

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