John,
Can you quantify the size of the "small spot" microXRF spectrometers?
Regards,
George
George M. Wenger
Reliability / FMA Engineer
Base Station and Subsystems Group
Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908) 546-4531
[log in to unmask]
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of John R. Sieber
Sent: Thursday, November 17, 2005 2:10 PM
To: [log in to unmask]
Subject: Re: [LF] XRF Equipment?
Rick,
As many of our LF participants know, IEC TC111 WG3 is developing a
standard test method that will include a method for XRF screening. The
goal is to provide a method that will enable users of any design of XRF
spectrometer to get at least semiquantitative results on whatever
material. The method is intended to help a facility decide whether to
use more specific test methods to get the answer. The successful WG3
method will provide some results that are clearly positive or negative
for the substances and a wide gray are where better methods must be
used. If successful, the method scope will encompass raw materials and
homogeneous materials within products. There will be language about the
concept of 'homogenization by grinding' of components. However, the
interpretation of results from ground up PWBs and such is quite
problematic. Nobody has yet convinced me that measurements of ground up
components and parts will yield any unambiguous answers.
Last week, ASTM F40 initiated a task group to develop an XRF screening
method for polymers. I expect their task to be easier than the WG3 task
because F40 is restricting themselves to one material matrix.
I know of people who plan to use XRF to screen parts for lead in the
finishes on leads and in solder joints. Some of them are using small
spot microXRF spectrometers. With such an instrument, they can analyze
a small location within a product. I think their major concern will be
the size and shape of the item being measured and its internal structure
(i.e.
layers or bulk, homogeneous or phase segregated, etc.) XRF works best
on flat, smooth surfaces that are larger than the X-ray beam. It is
also critical to know if the material is built of layers. Real samples
inside products will often have curved surfaces with no information
about homogeneity. It is conceivable that materials of interest will be
covering materials with very different compositions.
I am not saying that XRF analyses are impossible. I'm saying they are
not simple. For best results, the analyst must know XRF and the
software of the spectrometer must be validated. This is especially
critical if you want to buy a packaged solution such as a pre-calibrated
fundamental parameters method. Several people I know have investigated
the handheld and benchtop spectrometers. They report a significant
range of performance and ease of use. Personally, I have no experience
with these types of spectrometers used on the materials in question.
Long ago, I was involved with the use of low-resolution benchtop
spectrometers for fuels and lubricants. They were adequate for limited
product quality applications.
In my opinion, the real advantages of XRF in this arena are speed,
relative stability, and low labor costs. Once the XRF method is ready
to use, the measurements can be done by cookbook procedure. The
interpretation requires expertise. The instruments provide good
day-to-day reproducibility and measurements are fast. This makes trend
analysis easier and allows go/no go decisions within limits even if the
results are not super accurate.
In the end, you must decide if XRF will work in your situation. As a
member of WG3 and F40, I am interested to hear the experiences of those
who are using XRF for screening. You are welcome to send comments
offline, i.e. directly to me.
sincerely,
John Sieber
At 01:17 PM 11/17/2005, you wrote:
>We have had several customers ask if we are considering the use of XRF
>equipment as a screening tool for lead in components. Can anyone who is
>currently using or contemplating using XRF type equipment for analysis
>of lead content of unknown components comment on the usefulness of this
>technique as an additional inspection method? Is there significant
>differences between hand-held and benchtop installations in terms of
>accuracy? Is the method worth the expense?
>
>Thanks,
>
>
>Rick Thompson
>Sr. SMT Process Engineer
>CTS Electronics Manufacturing Solutions
>
>+1 (805) 532-2800 x-193
>[log in to unmask]
>www.ctscorp.com
>
>
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