SMART Events

A packed house, a sell-out event. 179 delegates from all over the UK reflected the rising tide of concern with a subject that has been well-aired, not least by the SMART Group, but which has yet to find commercial application in the field in this country.

The first of the eight excellent speakers was

Steve Andrews from the DTI who spoke about The RoHS Directive - Consultation, Compliance & Enforcement

Steve Andrews comes from the DTI Recycling Policy Unit and he highlighted the six key issues to be decided upon, of which more later. He explained the RoHS Directive, and the six hazardous substances, lead, mercury, etc. He looked at the scope of the RoHS Directive, and informed the delegates that there would be UK regulations in place by August 2004. The consultation period is now nearly over, he said, and the draft regulations and non-statutory guidance would be issued in the spring of this year.

The six key issues are as follows: -

Scope - there are ten broad categories in the WEEE directive. Where topics fall is clear in 90% of cases, but there is a significant 10% that fall into the 'grey areas'. Debate at EU level is difficult, but the DTI is hopeful that they will get the EU to agree upon a list of criteria that member states might use, by end of March. Typically it is the UK who lead the debate!

Definition of producer - the definitions are: -

- one who manufactures and sells own brand
- one who resells under own brand
- one who imports or exports into the EU
- BUT there is a problem with inter-EU trade, internet sales and with how it fits into the WEEE directive.

The deadline of 1st July 2006 will apply to all member states, including those many Eastern European countries who are yet to be become full EC members.

Put onto the market.
Article 4.1 of the RoHS applies here. It will apply to: -
- All equipment leaving the manufacturers premises after this date.
- all equipment on sale to the final user.
- Goods leaving the factory gate (or entering the EU)
For full details refer to the EC Blue Book which is available on the Internet.
- Historic equipment will have to comply regardless.

Maximum Concentration Values
Proposed levels are: -
- 0.1% for lead, hexavalent chromium and mercury
- 0.01% for cadmium
- 0.1% for PBBs and PBDEs

Steve asked, "what does homogenous material mean?" His understanding is that ' by weight in homogenous materials" probably is the wording that will be accepted.
Steve said to the delegates that if any of them had any thoughts on this subject, he would be pleased to have them, even though the deadline for consultation had now passed.

Compliance
There is a UK contract underway with ERA Technology for the TAC study on enforcement. There are several methods that have been proposed. They are: -

- self-certification by manufacturers
- backed up by EU standards on agreed tests
- standards on reporting formats
- exchange of information
However, there is no point in UK-only tests, and none of these by itself is the answer, it will be a mix and match. Self-certification is the way forward possibly.

Enforcement
- there will need to be an enforcement body
- there will need to be an enforcement approach
- there will need to be testing methods. These exist, but which ones are the best and give the best results?

Steve said that he understood that the Secretary of State for Trade & Industry would be responsible for enforcement, the TSOA (Trading Standards Officers Association) having rejected the wearing of this particular mantle.

If you need more help, then Envirowise have programmes that you can download.
Try www.dti.gov.uk/sustainability Helpline telephone number is 0800 585794

In response to a question "Is there equivalent legislation in the USA?" he said that yes, there was, needless to say it had started in California, but was being looked at in the other United States, and both China and Japan were establishing full legislation on RoHS policy.

European LEADOUT Project - Bob Willis, SMART Group.

Essentially an update from Bob Willis, Technical Director of SMART Group; he reminded the delegates of the 6th Framework Programme - covering low cost lead-free soldering technology to improve competitiveness of European SME. This is technical support for benchmarking, for joint reliability, for best practice guides, for assessment of the benefits of nitrogen processing, and for failure analysis. The programme involves several companies, and no less than twelve industry associations.

Angus Westwater of Rohm Electronics talked about how you control your components and discussed the impact of lead-free on component. Rohm Electronics are developing a lead-free roadmap, showing the transition to lead-free for components, with a cut-off date. He explained that the route can be easily managed, and how potential leaded component scrap is reduced or eliminated. But, he concluded, a lead-free road map must be implemented by anyone involved with component assembly NOW!

Chris Hunt of the NPL warned of the potential pitfalls on the path to lead-free, such as component suitability -there were concerns about concerns about softening of polymer mouldings, discoloration of LED's. NPL had taken a look at the effect of lead-free soldering on LED's, such effects including discoloration, melting of leg finishes. On polyester capacitors of wound construction could be problematic, temperatures of 215oC led to physical deterioration. With electrolytic capacitors, the extra heat needed for lead-free extra distorts the base, and there is function loss on polyester capacitors due to high temperatures. With BGAs NPL were worried about out-gassing of moisture, and possibly some delamination inside the component. You do need to watch out for components retaining their integrity.

Component finishes - lead-free finishes gave acceptable results for solderability, process yields, moisture ingression, plating ductility - tin whiskers can either be solid, perforated or hollow, they can be straight but can come off in different directions, and he showed some typical examples.

Some devices nearing the end of their product life may not be converted to lead-free, cutting short their availability.

Solder joint reliability - SAC is the main alternative alloy to SnPb. But you do need to make comparisons, and global strain around component through thermal coefficient of expansion (TCE) mismatch is one of them; lead-free solder must be able to absorb global strain. Of all the lead-free solders, SAC gives highest reliability in solder joint strains. For high strain tin/lead is better, for lower strain rate SAC is better. As you will not be able to use tin/lead, use bismuth on the alloy that is better for higher strains.

Lead contamination. NPL had looked at lead-free joint failure due to stress through thermal cycling, with SAC this had been in secondary reflow due to the LMP phase, and NPL are looking at this cause of failure.

There is quick test for lead, by the way, using a special pencil containing sodium rhodizonate.

Another potential problem with lead-free solder is the formation of Conductive Anodic Filaments

Martin Allison of Senju Manufacturing (Europe) looked at the status of lead-free manufacturing in Japan and compared it to lead-free manufacturing in mainland Europe. Japan have various laws in place for the restriction of lead in solder and recycling, and their Road Map is JEITA 2002. They started with components, which will be lead-free by the end of 2004. Equipment will be using lead-free solder from 2003 and they will be totally lead-free in Japan by 2005.

Solder alloys being used now are SAC 87%, SnAg 7%, SnAgBi 2% for TV. Wave soldering is using 67% SAC, 22% SnCu, 7% SnAgBi, BGA reflow is all lead-free.

In Europe Matsushita are now lead free, Fujitsu in Spain will be lead-free by 2004. Pioneer and Sharp aim for complete changeover by 2004 throughout Europe, Sony in Hungary, Spain and the UK are going lead-free by end of February this year. Hitachi will complete their move to lead-free in Europe by the end of February this year; Sanyo and Canon already have products that are lead-free.

A look at non-Japanese companies in Europe and Scandinavia showed that in Norway there were trials under way; in Sweden there were some production and trials in medial and communication and automotive products. In Finland trials were taking place in communications, and automotive and security electronics, Estonia was heavily in lead-free.

In Hungary Epson are now lead-free. Germany is being a bit slow off the mark, but Italy has moved to lead-free in communications, and is trialling in other areas. France is at the trial stage for all fields, Portugal is trialling in the automotive and car hi-fi areas. In Spain subcontractors to Japanese OEMs are already lead-free, and trials are taking place in white goods, automotive, CEMs, components, in Europe, as in Japan, SAC predominates for wave, reflow and BGA soldering.

Answering a question on costs, Martin said that lead-free is more expensive. Bob Willis wondered what it would take to get the UK industry moving over to lead-free? A mad panic?! He commented that the supply chain in the UK is a circle that has to be broken somewhere and he was surprised at the attitude of UK SMT engineers towards lead-free.

He suggested that a link to www.smartgroup.org/leadfree2004/name.pdf would be useful.

Harsh environment applications for lead-free solder systems was the subject of a talk by Steve Brown of Cookson Electronics

These environments are in the automotive, aerospace, military medical and industrial fields, and involve temperature cycling, a corrosive environment which may include vacuum, vibration or both. Steve covered the range of temperature experienced in the automotive environment, and the implications for military use. Lead-free must meet performance requirements; no one needs tin whiskers in space!

SAC is the alloy of choice in most applications, but there are variations on the theme involving silver, bismuth, indium alloys and gold alloys for high-end applications. Steve took us on a comprehensive sweep through the various aspects of SAC, and its variations, costs, effect on tombstoning, the wider pasty range. There is, he said, no unique ' best solution' for every set of circumstances, tin-silver-copper is a good all-rounder, but every company must have room for something else. SAC is primary choice, but its behaviour leaves a bit to be desired. He listed some proposals for the prevention of interconnect failures: -

(a) change package design
(b) compliant joints
(c) underfills
(d) total encapsulation
(e) board design

Why do tin whiskers cause so much concern? Well, they cause short circuits, they can grow in ambient temperatures, there is no accepted accelerated test, and remember that products may be stored for many years before use. Nowadays automotive electronics are safety critical, tin whiskers are caused by compressive stress on the tin. Compression is caused by high stress coatings, deformation, intermetallic coating and thermal mismatch. Stress can relieved by reflow, the use of a matt tin finish, a Ni/Ag flash or a pre-bake @ 150°C,

In terms of intermetallic management, he said that the use of a conformal coating can mask a tin whisker, but there is still a problem with harsh environments. On a brighter note, he concluded by saying that the situation is better now than it was even one year ago. Another twelve months and who knows.

The acknowledged expert on product marking Kay Nimmo of Soldertec tackled the vexed question of lead-free and RoHS marking and labelling systems. This is indeed a complex issue, finding out what type of marking systems people would prefer. However the results of the survey were now in and available from
http://www.tintechnology.biz/soldertec/soldertec.aspx?page_id=1637&SelectedMenu_ID=73

Kay said that WEEE labelling will be put on all equipment after 13th August 2005. There were several options - CE marking, a crossed out dustbin, and smart chips - are all possibilities. Nothing has been requested officially from RoHS yet, it is still under discussion.

Whilst there is no legal requirement for marking for lead-free, how do you demonstrate compliance? It may well be an industry requirement - but this requirement can vary within the supply chain, it depends on the viewpoint of manufacturers, distributor, assembler, recycler etc. There is no consumer marking.

Kay went on to explain about the difficulty in establishing an acceptable international labelling standard. There were various proposed JEDEC labels, and she suggested that a look at their website www.lead-free.org would be invaluable.

Mike Fenner of Indium Corporation looked at the practical aspects of lead-free soldering. He discussed some of the difficulties, and what you have to do to convert over to lead-free. Lead free is market driven, and you need to accept that this represents a fundamental change in the process of manufacturing your products.

Whilst there are some 200 alloys which have low melting points, the choice is pretty well made with SAC which has a melting point of 217°C compared to183°C for Sn/Pb. It takes longer to get to 217°C and it takes more energy to keep it there. There is an increase in delta T. Suitable PCB finishes include HASL, OSP, Organic Ag, ENIG, Pd/Ni, and Immersion Tin. You will need to consider poorer wetting, harder surfaces, longer times, higher temperatures, using the same equipment. Various options include a change of PCB finish, a change of components, and a change in solder paste.

His suggestion was to go away and practice quietly in a corner somewhere, and you need to do it NOW! There are many variables to consider, and you may well want to draw up a wish list for a lead-free solder paste, but you have to expect the unexpected. There will be new inspection criteria, as SAC alloys do not wet as well as the old ones, they are more cohesive. Mechanical properties are different, they are stronger but they are less compliant, and failure models are different.

Mary Gregory from A & D Automation encouraged the view towards vapour phase soldering with lead-free. She looked back to the early machines that were crude and difficult to operate. But nowadays VPS as a means to transfer heat is too good to ignore; it provides efficient heat transfer using perflurorcarbon liquid, which is healthy stuff.

Nitrogen is no longer needed. An inert vapour atmosphere in vapour phase soldering gives the best possible solder reflow conditions, where the Delta T is as close to zero as it is possible to get. The IOR pre-heat, variable heating levels, and Soft Temperature Rise allows you to control the temperature rise at 6° per second and there is an economical reflow alternative for high volume SMD manufacturers when they are considering their alternatives for lead-free solder reflow.

New VPS equipment can produce a board every 20 seconds. For lead-free no modifications are needed, all you do is change the liquid to one with a boiling point of 230°C. Is the vapour expensive? No, said Mary, it costs about 1.5p per minute for the vapour.

Helmut Leicht, Managing Director of the manufacturers IBL, covered some of the problems associated with lead-free which included temperatures exceeding 230°C and wetting problems. Whilst traditional convection reflow equipment is already installed, and the process knowledge is well founded, if equipment has to be replaced then the problems associated with overheating and bad wetting will be eliminated by the use of an inert gas.

Vapour Phase has some disadvantages, in that no high volumes are available and VPS is not a mature process in the field. However, these can easily be outweighed by the facts that the equipment can be used immediately, there is absolutely no risk of unsoldered joints, no risk of overheating, and there is the best possible wetting in a 100% inert gas atmosphere in a sealed container.

VPS joints typically show finer structure and less oxidation, and wetting is better too.
Densely populated boards solder superbly with VPS but not with convection ovens. With VPS you get excellent heat transfer through layers with less risk of 'popcorning' of different materials with the lower temperature of reflow at vapour phase, and good temperature pressure in the best thermal environment.

Inline machines are now available, and Herr Leicht was keen to emphasise that VPS is worthy of serious consideration when considering equipment replenishment with lead-free soldering demands.

That another 50 people wished to attend and had to be turned away indicates the fast-growing awareness of the vital importance of the move to lead-free soldering. The concept of lead-free has been around for a very long time, but it has been left to the SMART Group, amongst a few others, to bring the need for ' action this day' to be the call, rather than "we'll have a look at it next week".

The facts and figures given in the paper from Martin Allison of Senju accurately indicates the position of the UK. It makes worrying reading. It is not that the industry will not move to lead-free, for it knows that it has to. But it seems to be leaving it all rather late, and other countries who have positioned themselves to meet the demands of to-day will benefit whilst the UK pursues the "jam tomorrow" philosophy.

Report written buy John Ling
Soldering & Surface Mount Technology
Emerald Group Publishing Limited.