The new Group already has 95 members, many of whom are experts in soldering technology and have been previously associated with other networks such as the European ELFNET initiative coordinated by Soldertec.

Sub-groups created so far include the important topic of lead-free solder reliability. Its 63 members include top researchers from Europe and the US who have begun to highlight issues such as tin whiskers, and combined loading conditions.

The forum can become a place to share news, articles and experiences as well as gather input on technical questions from peers.

To join visit the reference link below and sign in or join LinkedIn.

The regulations work via a 'catalogue' of product types and a set of certification laboratories. The first entries in the catalogue, published last year, were phones and printers. Already items shipped to China use EIP labelling to indicate compliance.

Over the next 2-3 months enforcement procedures are being prepared, considering first a set of Guidelines and then choosing a certification body. Enforcement itself may be similar to the approach of some EU countries in enforcing RoHS - to work with the industry rather than be adversarial.

Industry consultations are already underway for the next set of catalogue additions, likely to be televisions and DVD players. These will be added possibly by the end of the year.

A guide to China RoHS has been

SAC305 balls were reballed with SnPb balls using three different methods. Their thermal cycling behaviour was compared with non-reballed lead-free BGA's assembled with SAC305 and SnPb paste.

For the same component type reballing method made no difference and the non-reballed SAC305/SnPb mixed assembly products were the same as, or in fact marginally better than, lead-free SAC305.

However, reballed SnPb assemblies were worse.

Microstructure analyses are discussed. Failure was within the bulk solder on the component side in each case showing that the reballing itself was not responsible for crack propagation.

The paper has been published online by the Journal of Electronic Materials - see the reference link below.

The standards do not have any exemptions and remove all SVHC's (Substances of Very High Concern). They also require elimination of TBBPA, the most common flame retardant used in circuit boards. A number of other rigorous criteria are to be applied.

Although in fact they only apply to imaging equipment and televisions, IPC are highlighting the fact that they fall under the umbrella of EPEAT (Environmentally Preferable Electronics Assessment Tool) that has recently been mandated by President Obama to be used for all government procurement.

IPC are concerned that these stringent requirements are being decided upon by 'only a sma

Despite efforts, particularly in the US, to narrow the number of lead-free solder alternatives, there rather been an increasing proliferation of alternatives. These have largely been lower cost low-silver products with different dopants used to compensate for lower performance. Other developments include 'high reliability' nanocomposite solders and now even 'magnetic' solders.

The SPVC white paper prescribes general requirements for determining critical physical and mechanical properties of bulk lead-free solder alloys. The document describes material tests that generate portable data for: (1) direct comparison of different alloys; (2) aiding in alloy acceptability determination for various applications; (3) development of re

Contributors to the Guidelines include Celestica, Alcatel-Lucent, Freescale, IBM, Meadville, Nihon Superior, Phillips Medical and Sun Microsystems. The document contains a compilation of best-known design and manufacturing methods as well as material selection recommendations based on industry experience with Pb-free assembly to date.

This version of the report addresses many of the issues associated with transitioning high reliability and currently legislation exempt products. This results from work published last year by Alcatel Lucent, Endicott Interconnect Technologies, Flextronics, Siemens, Celestica, IBM and Sun Microsystems on SMT reflow process parameters for high

The study from University of California and San Jose State University uses results from a survey of in 2005. 109 responses were received from a broad spectrum of companies including OEM's and EMS, as well as research organisations and consultants.

By 2005 70% of respondents had already adopted lead-free solder for electronic or electrical products in response to international initiatives.

The report summarises the environmental case for substitution of lead and constructs models and scenarios for tradeoffs of the various impacts. These were used to evaluate respondents value systems in making decisions about implementation. Health, biodiversity, resource depletion

Until now it has not been possible to pre-alloy aluminium, for example, because it oxidises too readily. This new technique uses metal organic modified flux in solder pastes to react the metals directly into the solder during solder processing.

Co, Fe and Al were tested with stearate, oxalate and citrate.

It was found that Co and Al influence the supercooling but Fe had no effect. Co reduced the supercooling of the cast by around 10'C and affected the nucleation. Al retarded the solidifcation up to 185'C. Co and Fe were found in the resulting microstructure.

The German-government funded project was undertaken by Bosch,

A key issue in the implementation of lead-free soldering was the need for a marking standard amidst the significant complexities to inventory control amidst a sudden proliferation of new materials. It was especially important that lead-free products should be clearly distinguishable from leaded products, not only for compliance but also to avoid compatibility issues in assembly. It was further necessary to identify which lead-free solders and finishes had been used to avoid such problems in rework.

J-STD-609 was introduced in 2007 to resolve these issues. It contains a set of e-codes for different lead-free solders, b-codes for lead-free finishes and additional codes for base materials etc. Guidelines were laid out for exactly what sequence the codes should be used in together with where and how t

Rare earth (RE) elements such as Ce and La are abundant in China and new applications are strongly encouraged. They are known to improve properties of metals and indeed this has been demonstrated in lead-free solders.

Research on RE addition has now started to be published in Europe and the US. There is still some doubt as to whether they can alone give sufficient improvement to properties for all applications and a recent paper from Beijing University has suggested that they may cause tin whiskers.

The paper also discusses Zn addition and its ability to reduce undercooling and suppress Ag3n

This new generation of lead-free solders was first introduced in BGA's for improved drop-shock performance because they are more ductile. They also have lower copper dissolution rates.

However, conversely, they tend to have poorer wetting properties and can perform less well in thermal cycling reliability tests. Hole-filling for thicker joints in wave soldering has been a particular concern.

To tackle these issues there has been a race to find elemental additions that can restore these properties, with Ni, Bi, Ge and more recently Co being the best known of several solutions. Chinese research has focussed on RE elements such as Ce and La.

This has inevitably generated a new set of patent issues that have hindered more widespread implementation of low-silver alloys.

Low temperature solder alloys systems are perceived to be desirable, not only to save process energy, but because for some lead-free solder systems there have been concerns over temperature-sensitive components.

The system described in the patent is based on the well-known metallurgical phenomena that rapid quenching produces solid solutions rather than higher-melting eutectic intermetallic phases.

Others have also looked at metastable solder systems. For example, BMG's (Bulk Metallic Glasses) are rapidly quenched alloys that have been shown to have remarkable properties for several metals. Intel

Using complex mathematical simulations a case study was used to model the interactions between thermal fatigue reliability and joint shape factor. This means that joint shape should be designed to control the failure mode.

Thermal fatigue testing is a common reliability test method for electronic assemblies and enables some prediction of actual joint lifetimes. It has been used extensively in development of lead-free solder alloys and continues to be a benchmark for new generation solders.

This means that work done on BGA's for example, using solder balls cannot necessarily be compared directly with tests on the same alloy using, for example, gull-wing joints.

On a typical PCB there are a variety of joint shapes and it must be remembered that it is the weakest that will break first,

High-lead solders are still exempted from the EU RoHS regulations for electronics because it has been commonly recognised that suitable alternatives are not available.

Any new solution will require extensive testing and qualification, for which it makes sense to collaborate. By working together the DA5 consortium hopes to reduce time for finding and qualifying solutions needed by customers.

The conosrtium has already worked together in the past on lead-free issues as 'E4/5'.

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The product is a hydrid between conductive adhesive and soldering technologies. A mixture of two metal powders within a polymer adhesive is heated to form a polymer-metal matrix composite. The two powders are one high melting and one lower melting, for example copper and tin, which combine together by a process technically called Transient Liquid Phase Sintering (TLPS). A third element can be added to refine the metallurgical processes.

This technology is important because there are very few commercially available alternatives to AuSn as replacements for high-lead solders used in such applications. Indeed high-lead solders are currently exempted from the EU RoHS legislation for this reason.

Several academic and indust