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An Overview of the Current Status of Lead-Free Assembly and Related Issues 
(Dr. Martin Goosey, Circuit World)

Abstract
With the formal adoption of new legislation by the European Parliament, nearly all electronic goods entering the European market will have to be lead-free by July 2006. Envirowise has sponsored this paper as part of its co-ordinated activities to assist the UK electronics industry and to promote environmental efficiency and best practice. The paper details the current situation towards the adoption of lead-free assembly. The main options, issues and changes associated with such conversion are outlined.

 An overview of the Current Status of Lead-free Assembly and Related Issues


(Committee Draft) Procedures for the Determination of Levels of Six Regulated Substances in Electrotechnical Products, IEC 62321
(IEC TC 111 Working Group 3)

Abstract
Recently, the RoHS directive is pressing the requirement for management and provision of material composition data. Besides, EU directives seem to be the pioneers of global environmental programs, various directives and laws are emerging outside EU (China, US, Japan, etc.). Hence, testing about the material content of all components and materials used to manufacture electronic products is being requested and results are shared across the entire supply chain continuously. Certain test procedures to determine regulated material content already exist, but most are not appropriate for testing electrotechnical products and are not internationally recognized. The purpose of this normative document is to provide test procedures that will allow the electrotechnical industry to determine levels of the regulated substances in electrotechnical products on a consistent global basis.

For more information, pls. visit IEC (International Electrotechnical Commission): http://www.iec.ch/


Test Procedure Flow
Source: IEC TC 111 Working Group 3
The figure below describes the flow for the test procedure to determine the levels of regulated substances in electrotechnical products.


Analysis Methods of the hazardous substances in Electrotechnical Products suggested by IEC 62321
The verification test procedure is performed after a mechanical sample preparation using a variety of analytical procedure tailored to the regulated substances and the material of the sample, which can be either polymer materials, metallic materials or electronics.

 

Polymer Materials

Metal Materials

Electronics

 PBB / PBDE

 GC / MS
HPLC / UV

N/A

 GC / MS
HPLC / UV

 Cr VI

 Alkaline Digestion / Colorimetric Method

Spot-test procedure / boiling-water-extraction procedure

 Alkaline Digestion / Colorimetric Method

Hg

ICP-AES, ICP-MS, CV AAS, AFS

Pb / Cd

ICP-AES, ICP-MS, AAS



Screening
Source: EU RoHS Enforcement Authorities Informal Network
As a first step, producers may choose to use a screening tool, such as energy dispersive x-ray fluorescence (ED-XRF) analysis. This tool has been widely promoted as a simple low cost analysis technique, but the results may only give an indication that a particular product / component may or may not present a potential compliance problem. It may not, for example, be sufficient to discount the possibility of an infringement of the RoHS requirements where one or more of the substances are present in both an exempted and restricted application. It will also not differentiate different types of brominated flame-retardants or identify the valence state of chromium.

The limitation of XRF techniques must be understood and taken into account. In general bench-top laboratory systems provide greater accuracy and the ability to analyse smaller areas (<0.5mm2) than handheld units. In either case the use of a standardised protocol based on suitable test procedures (and using certified reference materials to show correct application where possible) by a trained operator is essential. 

It is important that ED-XRF analysis is carried out correctly as misleading results can be produced if the limitations of this technique are not understood. Producers and enforcement authorities might wish to follow any adopted industry standards. The sort of screening analysis described above should be used to establish a "pass", "fail" or "borderline" result. No further analysis by producers should be required if a clear pass or fail is obtained, but additional more accurate analysis might be needed if enforcement authorities are considering further enforcement action. Additional analysis will be needed, however, if a borderline result is obtained.


Sampling Strategies
Source: EU RoHS Enforcement Authorities Informal Network

As a typical electronic product may be made up of hundreds or thousands of homogeneous materials, complete testing of the product is usually impractical - due to cost, time and sample preparation constraints. To address this challenge, the following three practical sampling strategies are recommended:

1 Focus on samples from know "high concern" materials and applications. It is generally not worth either the time or resource to analyse materials for substances that are not likely to be present.
2. Focus on samples that can be separated from the equipment using those ordinary tools that would be typically found in an analytical and testing laboratory or by techniques such as sectioning.
3. Where it can be demonstrated that it is not possible to mechanically disjoint a particular component or part due to its very small size or some other constraint and analysis of individual homogeneous materials is not possible, then this component or part is to be regarded as one homogeneous material. In such cases, the use of homogenizing techniques for components and parts that are composed of two or more homogeneous materials might be considered.

Current Tin Whiskers Theory and Mitigation Practices Guideline
Source: JEDEC / IPC Joint Publication
This publication provides guidance in understanding the prevalent tin whisker formation theories, driving forces and mitigation practices used to minimize tin whisker formation.

Sn whiskers have been an industrial concern and interesting problem for many years. They are know to cause short circuits in fine-pitch pretinned electrical components. Sn whiskers grow by the addition of material at their base not at their tip. They can grow from as-formed electrodeposits, vapor deposited material, and intentionally deformed coatings of Sn. Whiskers appear to be a local response to the existence of residual stress. Annealing or melting may mitigate the growth for an undetermined period of time. Legislation that will restrict the use of lead in electroinic products sold in the European Union, due to be in effect on July 1, 2006, has led many electronic component suppliers to propose the removal of Pb from tin-lead plating, leaving essentially pure Sn. However, for the high-reliability user community, the pure tin strategy presents reliability risks due to the whisker forming tendencies of pure tin and tin alloy plating.

Adaptation to scientific and technical progress under Directive 2002/95/EC
Source: The European Commission
A report has been published by the EU on the reasons for the recent changes in exemptions to the RoHS directive. This 148 page report details the case made by each requestor, supporting evidence, the process followed, and the final decision. It is another invaluable tool for any company that might want to seek an exemption.

Oko-Institut e.V. and Fraunhofer Institute for Reliability and Microintegration IZM have been commissioned by the European Commission with technical assistance for the evaluation of requests for exemptions submitted according to Article 5(1)(b) of the RoHS directive. The main objective of this technical assistance consists in a clear assessment of whether the requests for exemptions are justified in line with the requirements listed in Article 5(1)(b) of the RoHS directive.

According to the report, a total of 88 requests were evaluated, 27 requests were recommended to be granted and 38 requests were recommended to be refused. 17 requests were withdrawn by the applicant. For 2 requests the evaluation procedure was not applicable. A final recommendation for 4 requests was not possible due to lack of information.

The requests can be divided into the following thematic categories:
1. Solder Technology and Processes (25 requests)
2. Glass Technology (11 requests)
3. Metal coating / passivation (3 requests)
4. Electronic devices (12 requests)
5. Other / Miscellaneous (14 requests)
6. Lighting (6 requests)
7. Last Time Buy (17 requests)

To take a look of the final report, please visit:
http://ec.europa.eu/environment/waste/pdf/rohs_report.pdf 

How Halogenated Flame Retardants work?
To understand how flame retardants work it is first necessary to see how materials burn. Solid materials do not burn directly: they must be first decomposed by heat (phrolysis) to release flammable gases. Visible flames appear when these flammable gases burn with oxygen (O2) in the air. If solid materials do not break down into gases, then they will only smoulder slowly and often self extinguish. Materials such as wood do in fact burn vigorously, because once ignited the heat generated breaks down long-chain solid molecules into smaller molecules which transpire as gases. The gas flame itself is maintained by the action of high energy "radicals" (i.e. H+ and OH- in the gas phase).

Halogenated flame retardants act by effectively removing the high energy "radicals" in the gas flame phase. This considerably slows or prevents the burning process, thus reducing heat generation and so the production of further gaseous flammable material. 

When exposed to high temperatures, the flame retardant molecule release bromine (Br) or chlorine (Cl), as free radicals (Br- or Cl-) which react with hydrocarbon molecules (flammable gases) to give HBr or HCl. These then react with the high-energy H+ and OH- radicals to give water and the much lower energy Br- or Cl- radicals, which are then available to begin a new cycle of H+ and OH- radical removal. From the above mechanism, it is noted that the effectiveness of halogenated flame retardants depends on the quantity of the halogen atoms they contain (e.g. 10 bromine atoms in one molecule of Deca-BDE) and also, very strongly, on the control of the halogen release. Because chlorine is released over a wider range of temperatures than bromine, it is then present in the flame zone at lower concentrations, and so is less effective. Bromine is released over a narrow temperature range, thus resulting in optimal concentrations in the flame zone. 

Screening Limits for XRF spectrometry
Source: IEC TC 111 Working Group 3
Screening analysis allows one to distinguish between samples in three basic classifications:
- Pass: samples that safely contain concentrations, which are below the threshold values.
- Fail: samples that are clearly higher than the threshold values.
- Inconclusive: samples that require additional investigation, due to inconclusive analysis results.

IEC62321 recommends the following screening limits (mg/kg) when adopting XRF spectrometer

Elements

Polymer Materials

Metallic Materials

Electronics

Cd

P <= (70-3s) < X <(130+3s) <= F P <= (70-3s) < X <(130+3s) <= F LOD < X <(250+3s) <= F

Pb

P <= (700-3s) < X < (1300+3s) <= F P <= (700-3s) < X < (1300+3s) <= F P <= (500-3s) < X < (1500+3s) <= F

Hg

P <= (700-3s) < X < (1300+3s) <= F P <= (700-3s) < X < (1300+3s) <= F P <= (500-3s) < X < (1500+3s) <= F

Br

P <= (300-3s) < X   P <= (250-3s) < X

Cr

P <= (700-3s) < X P <= (700-3s) < X P <= (500-3s) < X