The phase-out of lead from electronic solders has been threatened for many years and now recent events, including both legislative and voluntary measures, have made this change crucial to the commercial electronics industry.
Directive 2002/95/EC of the European Parliament requires that after 1 July 2006, newly-marketed items of (consumer, office and IT) electrical and electronic equipment, shall not contain any lead or a number of other proscribed chemicals (note that initially products used in medical, defence, aerospace and automotive applications appear to be exempted).
While 2006 might seem to be still a long time away the change away from lead began several years ago with Nortel introducing a telephone using lead-free solder in 1997 and Panasonic introducing its first lead-free soldering line in late 1998. Panasonic specifically has reported that it encountered no problems regarding reliability of the initial product (a portable MiniDisc) with 40 000 units being produced every month, and it also stated that defect rate was half of that originally expected. While the EU Directive did not address military electronics the first meeting of the European and US Lead-Free Solder Interface Group took place in March 2002, the objective being to identify lead-free solutions for the defence and aerospace sectors.
In May this year, Matsushita Electrical Industrial announced that it had completed its switch-over to the use of lead free solder for its Panasonic and National brands. Since the company first introduced lead-free solder it has produced more than 70 million devices using this technology on the printed circuit boards. Today, more than 12 000 product models are produced using lead free solder and the company expects that this year more than 80% of the solder used will be lead-free.
Of some concern to users of lead-free technology must be the claim from Matsushita that it has submitted more than 337 patent applications related to the process and is thus 'in a leading position in the field'.
Another Japanese company that has been proactive is Omron (industrial automation, healthcare and electronic components), its initiatives being based on its own environmental policy rather than the EU requirement. By 2001 Omron had already proved the validity of lead-free soldering and plating technologies for 42 products and research is continuing on developing low-temperature lead-free soldering technology for use with low heat resistant components. Omron found that it was important to use equipment that can minimise temperature variations during reflow/flow processes and special soldering irons were introduced for manual soldering. The main focus to date has been on tin-silver-copper and tin-copper solders with minor additives.
Sony, as another example, started to introduce semiconductor products with lead-free terminals from 2000 onwards. Both surface mount and through-hole devices have progressively been modified with tin-lead plating being changed to a tin-bismuth combination. Sony recommends that the maximum temperature during mounting processes be 260°C (previously 240°C) for both re-flow and flow soldering processes. In fact, local South African suppliers of equipment suggest that in order to achieve adequate time above the solder melting point and to stabilise temperature, that a five-zone oven be used, three of these zones being used for preheat and two for reflow.
How green?
It also appears that some lead-free solders may also require an inert gas such as nitrogen in the process and this could be an expensive consumable. It is interesting to note that to generate nitrogen the fuels used and their emissions are probably much more toxic than the amount of lead used in electronics, but the Green Movement is having its way and South African exporters of electronic equipment to Europe will have no option but to abide by the Directive.
The most likely alternatives to the traditional tin-lead are tin-silver-copper or tin-silver. Apart from many other differences, what is significant is that while conventional solder melts at 188°C, the melting points of the replacements is between 217 and 221°C. Most electronic components on the other hand are typically specified to a maximum temperature of between 240 and 250°C. With hand soldering, care must obviously be taken, although one guide that I have read on conventional electronic soldering recommends a soldering iron tip temperature of between 350 and 370°C, minimal contact time limiting excess transfer of heat to the components.
The problem of hand soldering using lead-free material has actually seen some major advances in the technology of the conventional soldering iron. These devices traditionally operated at constant power with the ability to set the tip temperature. As soldering takes place the actual tip temperature decreases and operators tended to set the tip temperature high to increase efficiency. But this can obviously cause overheating damage to components and boards. The latest technology soldering irons keep the tip temperature constant and not the power supplied to it.
The innovative way of doing this is to make use of a tip constructed from a non-heating copper core with an outer heating layer of magnetic alloy. The alloy makes use of its Curie point temperature to retain its conductivity properties with the tip temperature being maintained to within ±1°C of the set point, irrespective of load. Such irons can thus be set to operate in the 215 to 220°C range required by lead-free solders thus minimising the risk of damage to components.
Local viewpoint
From the viewpoint of the local industry it is important to note that Europe is not always the target market and re-engineering successful products to meet the deadlines may not be done voluntarily. However, it is important to note that the source of components containing lead will diminish with time and this may leave companies with an even worse option of having to solder electronic assemblies with mixed (lead and lead-free) technologies.
As regards equipment, lead-free compatible reflow and wave soldering equipment has been available for several years now, so any company that has recently upgraded its facilities is well on the way. For most companies in this situation what will be required is new solder baths as it is difficult and expensive to flush out and clean old ones. It is possible however, according to equipment manufacturers, to use the same wave solder machine with two easily changeable solder baths, so that if required in the interim, both processes can be continued.
Another local problem exists for the contract manufacturers who are on one hand being faced with the component manufacturer's move towards lead-free and a decreased availability of traditional leaded components. At the same time their customers are reticent to move in this direction as only the EU has taken the step of implementing legislation. This 'wait and see' attitude coupled with Japan's unconditional acceptance for environmental reasons and America's close watch on developments in Europe could ultimately be detrimental to the local electronics industry.
PCB makers
In terms of the local PCB manufacturers, they indicate that there is still major demand from local companies for the traditional hot air solder levelling which is of course, not a lead-free process. Many suppliers have installed capacity for the newer (lead-free) immersion tin and also electrodeless nickel gold processes. In the case of the former, some customer demand has arisen but it is believed that this is as a result of the flatter profile obtained and its better suitability for BGA rather than environmental concerns. In many cases, local PCB suppliers also import special boards from overseas companies and they indicate that these suppliers also seem in no great rush to implement the EU Directive. One well-known PCB manufacturer indicated that it has had only a single enquiry about the local availability of lead-free processes.
Contract manufacturers
Local contract manufacturers have indicated that they are driven by the needs of their customers and as yet the demand for using lead-free solder for population of boards is non-existent. In-house manufacturers that have made substantial recent investment in new SMD soldering equipment, such as Shurlok, have no doubt prepared themselves for the changeover but in Shurlok's case its market is automotive that is currently exempt. Other local companies such as UEC that have major exports to Europe and other geographical regions will no doubt be forced to comply, but with this company's exponentially increasing production, its solder lines are surely already compatible.
There is no doubt that our well established and growing defence electronics industry will continue to use the well-proven lead soldering techniques and will be a follower. If lead-free technology is ever forced into this sector, MIL-SPEC qualification costs will be significant and an extensive period of time will be required to ensure solder joint reliability and MTBF. As the defence forces of the world use munitions (including, for example, depleted uranium) that are much more harmful to the Earth's environment, it may be that introduction of lead-free technology for electronics will continue to be seen as totally irrelevant, after all, a small amount of lead is hardly equivalent to a 'weapon of mass destruction'.
In conclusion, it would appear that the larger companies that are used to frequent investment in new and more efficient soldering capability should have no problem in meeting the 2006 deadline. The smaller entities using older soldering equipment may find the investment in new solder lines not cost-effective and may be persuaded to follow the already growing contract manufacturing process if they are exporting into Europe. However, for many of these companies, their market is domestic or southern Africa, and the real pressure for them will only arise when (and if) leaded components eventually become unobtainable. Overall, the local industry would seem to be as well prepared as European companies such as the UK.
Thanks is expressed to the many companies that participated in the preparation of this article, these include TraX, Tellumat, Central Circuits, Zetech, Techmet, MyKay Tronics, and many others.
© Technews Publishing (Pty) Ltd | All Rights Reserved
printer friendly version