With the spotlight on lead-free solder, oven capabilities are coming under tight scrutiny. But, just where does this really fit into the full reflow picture? Are there equally important issues pushing oven developments? As new capabilities are unveiled, what is being done to help existing customers optimize older ovens? To clarify these issues, seven major oven manufacturers agreed to share their opinions, strategies and latest equipment developments with EP&P.

The issue of lead-free is not so much the higher liquidous (standard eutectic 183°C; lead-free 217-221°C). Most ovens easily can handle the temperature. For those that may feel more confident with an added thermal "boost," high-temperature upgrades are available. But, higher temperature is not the point. The profile process windows are shrinking by as much as 30° because, as Marc Apell, product manager at Speedline-Electrovert, explains, "You can't ramp up to the maximum peak temperature of the solder range because it surpasses the limit for both component and board material tolerance thresholds. Therefore, it becomes more of a flat profile — held at the low end of liquidus over a longer period of time." (Fig. 1).

"This puts a significant emphasis on smaller product temperature differentials, increased oven performance and overall process repeatability to ensure quality output," adds Al Cabral, marketing, BTU International.

Oven manufacturers began working on this issue as soon as it arose, even though full implementation may be well in the future — and, may never pose the challenge it appears to be today. As they noted, lead-free is only in beginning stages, and there will surely be changes and improvements. Component, PCB material and paste manufacturers are all working on the issue. Because all parties have a common goal of easing product processing, it can be assumed that whatever advances materialize will benefit the reflow process. Moreover, today's significant challenges may not even exist in the future.

However, improvements driven by this issue will enhance overall oven capabilities in the long run. Improved designs and control software are in development. One key element comes from outside the inner circle of oven manufacturing-partner arrangements with profile OEMs.

Only a few years ago, profiling equipment was basically in use only at the larger OEM manufacturing facilities. Since profiling software and oven control software "spoke different languages," profiling programs ran on independent computers. Advances in software development, plus the looming specter of shrinking process windows, brought the two industry segments together to create "self-profiling" ovens. This partnering arrangement fans out across the whole customer base, so all ovens — old or new — have support from both the oven manufacturer and its selected profile provider(s).

If there is any single issue that oven manufacturers both agree and disagree on with equal vigor, it would be the area of profiling providers. All believe in the benefits, but, there are widely differing opinions regarding who and how many profile partners offer the best solution.

Fig. 1: Compared to a standard eutectic profile which hits peak quickly and cools down quickly, lead-free holds at low liquidus longer, creating a flatter profile.

SEHO has partnered with a single profile OEM. "We are partnered with ECD because, after reviewing all products, we believe they offer the best analyzing software," says Heike Schlessmann, marketing. "Also, both the hardware and the software are easy to handle, which is a benefit for our customers. Our new ovens are available with the program installed, and we also provide software upgrades, installation and training for customers with older ovens."

BTU has established working relationships with KIC, ECD, DataPaq and CMD. "We like to think that BTU helped pioneer the interface between profiling and oven control software," says Cabral. "A few years ago, BTU approached KIC and presented the idea of linking the oven to the profiler. In concert, we created compatible software interface modules that successfully communicate. This provides a 'self-profiling' reflow oven. Our first experience with KIC was successful and, soon thereafter, we partnered with ECD to a similar degree of success. We have since provided this same interface to a number of other partners."

Like SEHO, Rehm, USA has an arrangement with ECD only. "Our systems are all equipped with ECD profile generating software as a standard feature," says Sabine Berger-Eckle, marketing. "We compared the products available and decided that ECD provides the best solution to easily allow our ovens to adjust themselves for optimum reflow."

Vitronics-Soltec claims to be one of the first companies to see the benefit of integrating profiling and oven control software. "We have an open interface that we have discussed with all of the major profiling companies," says Eddy Nijhof, product manager. "We currently have installed ECD and KIC profiling suites onto our ovens." He explains that the reason for selecting these initial providers is because both profiling packages work from a known database of solder pastes. This is the normal starting point that all engineers use when establishing product profiles. "They do take a different approach on how to present their data; KIC uses a lot of multimedia while ECD is geared more toward the engineer. Ultimately, either is an excellent added feature to our ovens."

Fig. 3: SEHO’s flux elimination system condenses and collects all residues in a bottle for clean disposal.

Conceptronic is partnered with KIC and ECD. Their own profiling system is also a standard feature. "It's good enough for many of our customers," says Peter Whelan, VP Sales. "Others want more. The reason we partnered with KIC and ECD is that they both seem to keep up, in terms of software, and in profiling technology as a whole. In the long term, our goal is to tie the profiling software to extensive statistical process control programs. Both ECD and KIC are working on that."