Connection magazine sat down with Tait Manufacturing Engineering Manager Dean Mischewski to discuss how Tait switched to Lead-Free infrastructure assembly. Dean explains the process:
Lead is extremely toxic to humans – prolonged exposure can cause serious problems to your central nervous system, so it isn’t something we want to be handling unnecessarily. Unfortunately, it’s been used in electronic components for years, particularly in solder. So there is wide concern about how much lead the disposal of these devices might introduce to our soil and waterways.
Governments around the world have legislated to manage this problem, and Tait terminals have been lead-free for a decade now, under the European RoHS (Reduction of Hazardous Substances) legislation. In 2016, this law extended to include base stations, necessitating a switch to lead-free assembly to continue selling our infrastructure products into Europe.
Updating our wave soldering process required a particularly substantial investment. So began a major project to transition our infrastructure production processes to lead-free.
For years, the industry-standard way to make multiple through-hole solder joints in a short time has been a wave solder process. This involves conveying a printed circuit board assembly (PBA) across the top of a bath of molten solder. A pump spills a wave of molten solder over the edge of the bath, just touching the bottom of the PBA, and forming solder joints between the component leads and the metalized pads on the board surface.
Unfortunately, our 15-year-old wave solder machine was not designed for lead-free assembly, and was outside the manufacturer’s service life. So we had to consider our options: how would we maintain our infrastructure assembly capability in a lead-free world?
Upgrade the current machine?
We could have upgraded our wave solder machine to make it lead-free-capable, but this would have come at a fairly steep cost and would not have changed the fact that the machine had been officially retired by the manufacturer, and would no longer be actively supported.
Hand soldering was considered only briefly because the heat-sinking on many of the components means that the thermal demands for soldering exceed what can be done with a manual soldering iron. Even with a high-power iron, the time taken to form the solder joint exceeds the working life of the flux in the solder. Special fixturing or component forming tools would have been required, to allow us to hold components in place while a board was being soldered.
New wave solder machine?
Wave solder is a good choice for high-volume soldering of through-hole components, but our situation is medium-volume: too much (and too technically demanding) for manual soldering, but too little to justify wave solder. Since our current machine was purchased 15 years ago, a significant proportion of through-hole components have migrated to surface mount technology, so a new wave solder machine would operate for only a small part of each day to meet our demand. But it would require the solder pot to be active for much longer than that, meaning greater energy cost. The price is similar to a selective solder machine but wave solder is much less flexible, and does not provide selective solder’s cost reduction opportunities.
Selective solder machine?
This is the option we ultimately chose. Selective soldering is an automated process that solders individual joints or clusters of joints at a time. Instead of using a large pot of molten solder with a wave that solders the entire width of a board, selective soldering allows individual joints to be accurately soldered with a thin vertical “pencil” of molten solder. This technology not only satisfies our requirements for RoHS compliant infrastructure equipment, but it also reduces costs on other products that are not compatible with wave solder and would previously have had to be hand-soldered.
Having decided which technology approach to take, we evaluated many different machine models and came up with a shortlist of machines which met our requirements; safety, quality, PCB size constraints, throughput, and capacity, among other factors. We then visited other manufacturers using those machines, for an in-depth, practical assessment and – importantly – conversations with current users.
The selective solder machine we settled on was the Kurtz Ersa EcoSelect 1.
The key influencers of this this decision were that this machine has both top and bottom heaters (important due to the high thermal mass of our infrastructure products), additional nozzles, superior process control verification equipment, versatile software, a high number in use worldwide, and an acceptable cost.
The machine was successfully commissioned and now processes our main infrastructure assemblies, lead-free and RoHS compliant.
We can now look forward to a series of productivity improvements. Besides covering all our current wave solder machine work, we will be able to eliminate a considerable amount of hand-soldering on other products.
Ongoing expenses of a selective solder machine are less than for our current wave solder machine: lower energy cost, less solder use, less flux consumption, less dross/wastage, and less maintenance. And the new machine’s soldering is superior to both hand soldering and our current wave solder machine; it solders in an inert nitrogen atmosphere, producing exceptionally high-quality solder joints. This allows us to take an already-robust process to an even higher level, while complying with legislation to reducing the impact of electronic waste on human health.
Learn more about health and safety in the workplace, and how organizations are working to achieve Zero Harm with our informative white paper – Zero Harm – Health and Safety in the Workplace.
Take a look inside the Tait factory to learn more about how we create our tough radios and base stations for clients all over the world – Inside the Tait Factory.
Tait appreciates the combined importance of innovative progression, along with the importance of environmental responsibility. We strive to find the best means of achieving both. Read more about how we do this in our Environmental Policy.