XRF vs. Spark Test for RoHS Compliance Verification

[Eusoof]

I want to share my experience with my raw material supplier where i have use XRF machine to test if their material are compliance with RoHS requirement or not. From my finding that that raw material (lead substance) are exceed than 3500 ppm and then 3 times repeated test show the same result (note that xrf just for screening propose only). Then i have complaint to supplier that they said their use spark test that more reliable test than our. So my question are bellow :

1.)Although that XRF for screening purpose but show result same result (more than 3500 ppm) that means that material have problem?

2.)Can you share knowledge how to read the mill certtificate figure?

3.)What is spark test?

Thankz

[harry]

The results certainly look bad. In such circumstances, we normally have to ask the following questions:

• Is your instrument calibrated?
• Are you using the right or approved methods in your analysis? Sorry, but you sound rather green. Do you have recommended testing methods for RoHS?
• Is the material homogeneous?
• Are there any coating/painting over the tested area which may unduly affect the ray penetration and therefore results.
• Have you been trained for this purpose?

You should ask your supplier to show their test results or certificates from recognised independent labs and explain them. If you are not satisfied, you can arrange them to be tested at a lab of your choice.

I am not aware of what a spark test means but if XRF results are in doubt, the recommended method is to use inductively coupled plasma atomic adsorption or emission spectrometry (AAS or AES) method for more detail and accurate results.

[fireonce]

Originally Posted by Eusoof

I want to share my experience with my raw material supplier where i have use XRF machine to test if their material are compliance with RoHS requirement or not. From my finding that that raw material (lead substance) are exceed than 3500 ppm and then 3 times repeated test show the same result (note that xrf just for screening propose only). Then i have complaint to supplier that they said their use spark test that more reliable test than our. So my question are bellow :
...
Thankz

I think you are right.
As I know, XRF's precision is above 70%,and the result of your company is available,you are supposed to confirm with your supplier again.

The spark-test method specified in this standard is intended for the detection of defects in the insulation or sheathing layers of electric cables. For single core cables with no outer metallic layer, the general process is accepted as being equivalent to subjecting samples of those cables to a voltage test in water. This standard specifies the operational requirements for the spark-test equipment, as well as the principal characteristics, functional parameters and calibration procedures for each type of test equipment

[chergh]

XRF isn't suitable for quantitative measurement, it's semi quantitative at best. The 3,500 ppm figure you have is unlikely to be accurate so you need to send off your material to be analysed using ICPMS. Once you have that you can go to your supplier.

As for spark testing??? I think your supplier must have misunderstood you as how a spark test is going to give information on lead content is beyond me.

[harry]

The OP is referring to the Optical emission spectrometry (OES) using arc and spark excitation method and not the leakage test which has nothing to do with RoHS.

I am not familiar with this method although its being used quite extensively in the metal industry but had not seen it being recommended in any RoHS related documents.

[Benjamin28]

Optical Emission Spectrometry using arc/spark is indeed the preferred method for chemical composition analysis over XRF.

I wonder if your XRF is appropriately calibrated. I suppose if you really wanted to pursue it further you could have an independant lab analyze the sample and compare the results, somewhat like a round robin test.

Interestingly enough, spark testing in the old days used to be performed by operators who needed to quickly identify an alloy type, they would put the metal against a grind wheel and by seeing how long the spark was that it created, it's brightness and color they could determine what alloy they were holding. I'm certain your material supplier is using OES spark/arc and not the old spark method though lol.

What specifically are you asking about as far as interpreting certificate results?

One other thing, as stated in a previous post, XRF is semi-quant, meaning that you can find that XY elements are detectable at approximate levels, so your >3500ppm may well be incorrect as it is an approximation, whereas the spark test will tell you with much greater accuracy what % or ppm of that element is present.

[chergh]

Using oes is certainly better than XRF, just never heard oes methods referred to as a spark test.

XRF should be seen as indicative only and should not be used quantitavley. The official method for determining lead content for RoHS is ICPMS (inductivley coupled plasma mass spectroscopy). This is more sensitive than OES methods but at 1,000 ppm (maximum allowable concentration of lead from RoHS) you are magnitudes above the limit of detection even when using OES methods.

[harry]

Just check the China RoHS documents and OES is also not among the recommended method. To the OP (Eusoof - if he still visits this thread) you can reject your supplier's result and demand that he produce one using RoHS recommended methods or one from an approved lab. (Bear in mind that Sony usually accept only SGS lab. reports over here)

A number of methods are recommended in RoHS documents - each being suitable under different conditions. To clear the confusion, I attached here a document on RoHS testing methods for those who are interested.