TDK-Lambda Nieuws

This must be a question most component engineers and purchasers are asking themselves as the RoHS directive implementation date of July 2006 approaches. At Lambda UK verification is taken very seriously and the Component Engineering dept has taken a four way approach to this issue.

1. The creation of a master components database including all RoHS compliant part numbers, manufacturers self declaration information and results of in house verifications.

2. Collation of Third party analysis reports normally provided by the component manufacturer

3. Amending its regular Vendor Audit process to include checks for RoHS conformance procedures

4. Using an Energy dispersive X-Ray Fluorescence spectrometer, Fourier Transform Infrared Spectrophotometer and UV mini system for on site verification of any component to the RoHS directive.

Once Lambda UK had established the requirement for the detection equipment on site, the obvious questions were,

What components required testing using the equipment?
How often?
Which manufacturer’s test equipment to procure to verify conformance?

What to test?

Reviewing the master database of components Lambda categorised them by level of risk either of component or supplier not meeting the directive as detailed below.

High Risk:
? A component supplied as compliant, but without any evidence supported either from 3rd party analysis or from the manufacturer that it complies to the directive.
? A supplier or manufacturer of components or sub assemblies with either little, or no knowledge of the RoHS directive with no confirmed time scale for compliant components.

Medium Risk:
? A component supplied classed as RoHS compliant with supporting evidence provided by the manufacturer but not verified by an external 3rd party test facility (e.g. SGS)

Low Risk:
? Components with supporting evidence from a 3rd party test facility that shows they fully comply to the RoHS directive.

Like many electronics manufacturing companies across Europe, Lambda UK source many components or sub assemblies from Asia, predominantly China. While China is moving towards a similar control of lead free products the planned implementation date is at least 2007 or later. Components from this part of the world must be classified as high risk if no 3rd party documentation is provided. The control and auditing of manufacturers RoHS procedures must be on a regular basis to increase confidence that manufactured product complies fully to the directive.

When to test?

The Lambda UK policy

High risk

On site testing high risk product must be carried out on a delivered batch by batch basis. The quantity of product tested to the recommended Acceptable Quality Level (AQL) set for RoHS on site. The length of time required to continually check batches at high risk will depend on results from previous batch testing and the frequency that the product is purchased, but on average products purchased at regular monthly intervals should be tested for compliance for six to nine months and if all batches pass test then the component can be reduced from high to the medium/low risk category.

Medium risk

Product must be tested regularly for at least six months without any non conformance to verify the data provided by the manufacturer. The frequency of testing may not be every batch but will depend on the confidence level Lambda UK has with the manufacturer.

Low risk

Product with full supported documentation showing compliance for a recognised 3rd party test facility will only be tested at Lambda UK if advised by the manufacturer that contamination of product may have occurred and shipped to Lambda UK mistakenly.


The verification equipment

Lambda UK has worked closely with Shimadzu UK for the past few months to provide a full non destructive (where possible) solution to verification.

The EDX700HS is an Energy Dispersive X-ray fluorescence spectrometer (EDX) and can perform qualitative and quantitative element analysis. It can be used with solid, powder and liquid samples. This is achieved by applying X-ray to the sample and then analysing the re-emitted element characteristic fluorescent X-ray. Many security functions effectively prevent exposure to X-rays at all times.
With a simple push of a button, elements ranging from sodium to uranium can be analysed quickly and easily. In addition, the software enables measuring conditions to be adapted to the sample characteristic. For precise analysis of lighter elements the system is operated under vacuum. The built-in five-filter assembly (zirconium, aluminium, titanium, nickel and molybdenum) effectively reduces interferences and increases the signal quality. This way, the limits are markedly improved for detection of e.g. lead, cadmium, chlorine or chromium.
The large sample chamber accepts samples up to 300 mm diameter and 150 mm height and sample turret for up to 16 samples.
The detector system requires liquid Nitrogen (N2). For the measurement of small samples, the X-ray is decreased easily using optional collimator assemblies ranging from 1, 3, 5, to 10 mm
The exact positioning of small samples is easily monitored accurately using a colour CCD camera.
The EDX system enables analyses of mercury, cadmium and lead in polymer building parts (such as casings and cable insulations) down to the ppm range. During EDX analysis, hexavalent chromium, PBB (polybrominated biphenyls) and PBDE (polybrominated diphenyl ether) are detected as elemental chromium and elemental bromine and must be subjected to further tests to determine whether or not a banned compound is present.

Detection of polybrominated diphenyl ethers (PBDEs)

According to the RoHS directive, the following compounds are considered as hazardous: pentabrominated diphenyl ether (PentaBDE) and octabrominated diphenyl ether (OctaBDE) which have been used in polymers such as ABS and PS. Currently, decaBDE is largely being used as a flame retardant in PS, PE, ABS and polyester. DecaBDE has not yet been included in the RoHS directive. However, commercial decaBDE consists of a mixture of approximately 97 % to 98 % decaBDE and up to 3% of other BDEs. Therefore, when a polymer contains 10% decaBDE (containing 0.3% contamination of other brominated BDEs), the PBDE content will exceed the RoHS threshold value of 1,000 ppm.
In order to comply with the requirements of the RoHS directive, the total bromine content of a sample is first determined. If this exceeds 5 % after the preliminary examination using the EDX system, infrared spectroscopy is used at Lambda UK which will enable identification of compounds.
This simple and non-destructive method quickly leads to useful results. Compound identification is possible as the flame retardants were present up to now in polymers in concentrations of higher than 5 %. This level is still detectable in polymer mixtures using FTIR. Using this analytical method the total concentration of elemental bromine in the sample is detected, although it is not possible to distinguish which compound actually contains bromine. When more than 5 % of total bromine is detected, FTIR can be used for further identification of bromine compounds.
Measurements are carried out using the single reflection ATR accessory DuraSamplIR-II System. The plastic sample is pressed directly against the prism for analysis, with the results as shown below.

Absorption spectrophotometry measurements of hexavalent chromium using the UVmini-1240 Spectrophotometer from Shimadzu.

The system includes the ready to use packed reagent which is based on the JIS(Japanese Industrial Standard) method using diphenylcarbazide as the colouring reagent. So, the complex pretreatments are not necessary anymore with this system. In addition, the preparation of a calibration curve with the standard samples is not necessary (because the calibration curve is built in the system), this makes the measurements easier. Measuring the hexavalent chromium in the commercially available chromate treated screws with this system can be achieved.

While Unichrome is a chromate treatment, almost no hexavalent chromium is extracted from Unichrome plated screws. Unichrome is brilliance chromate treatment that is often seen as a shiny silver finish. The greatest amount of hexavalent chromium is extracted from coloured chromate-treated screws. Those are also commonly seen and appear as a shiny yellow colour. General trends indicate that a longer extraction time or higher extraction temperature achieves a greater amount of hexavalent chromium extracted. For example, the graph shows the differences in hexavalent chromium extraction due to different extraction times at an extraction temperature of 80°C. The extracted amount of hexavalent chromium is indicated as micrograms per gram of screw sample. It is generally known that plating colored chromatetreated ones have high content of hexavalent chromium, while Unichrome plating contains almost none.

The Shimadzu package of instruments and other measures described in this article will provide confidence for customers of Lambda UK that we are meeting all the requirements of the RoHS directive.

Richard Kenshole
Component Engineering Manager
Lambda UK

References to the Shimadzu equipment have been approved by
Shimadzu UK branch
Unit 1A Mill Court
Featherstone Road
Wolverton Mill South
Milton Keynes