Using Technology to Enhance Customer Value in SMT Production

Using Technology to Enhance Customer Value in SMT Production

By Dipak Patel, owner/manager, and James Boyd, process engineer, Krypton Solutions

Krypton Solutions is a contract manufacturer (CM) in Plano, Texas specializing in electronics assembly for the semiconductor, medical and industrial market segments. The company provides services ranging from engineering support and pilot production to production runs in a high-mix/low-volume and quick turnover environment. It currently operates three SMT lines with plans to expand to a fourth production line later in the year.

Company Goals

Krypton Solutions operates in a highly competitive marketplace for electronics assembly services. The company prides itself on using advanced technologies to exceed its clients’ demands for high-quality, cost-effective solutions. As a result, in 2011, it made investments to enhance the capabilities of its reflow process — specifically, the validation of the oven process by better measuring and documenting the profiles of the assembled printed circuit boards (PCB). While its Heller 1913 Mark III is a sophisticated reflow oven that provides excellent control and stability, the machine’s ultimate goal is to yield the correct profile for each PCB. Krypton Solutions wanted to document the hard-to-get profile information on an ongoing basis and realized that the traditional method of spot checking the thermal process left it running blind in periods. Beyond the production benefits associated with upgrading its thermal process to a best-in-class capability, the company saw a business opportunity in acquiring new contracts from demanding clients that value process control and documentation. Secondarily, it wanted tools that could provide better information and insight into reflow processes that, in turn, would lead to both quality and productivity improvements. The thought was that once the company understood its ovens and could measure the behavior of the PCB profiles, it could improve upon them.

Investment

After initial research, Krypton Solutions decided to purchase a continuous thermal management system for all its reflow ovens. The chosen system was the KIC RPI and KIC Explorer with Auto-Focus. The RPI was installed on its three reflow ovens in April 2012. The KIC RPI uses built-in sensors in each oven to automatically measure the profile for every PCB produced. Each profile is displayed and stored on the PC. The stored profiles can be retrieved based on a date and time stamp or, alternatively, when the PCBs come equipped with bar codes, the relevant profile pops up when the bar code is scanned. System programming is performed by an initial manual profile using the KIC Explorer, which doubles as a process improvement tool. Essentially, the tool reviews all possible combinations of oven zone temperatures and conveyor speed and selects the recipe that positions the profile deep inside the process window that Krypton Solutions establishes based on solder paste specs and component tolerances.

Production Impact at Krypton Solutions

The KIC RPI automatically provides real-time profiles for each PCB as they exit the reflow ovens. The profile specs are measured against the established process window for each selected dimension such as peak temperature, time above reflow, slope and more. Because its PCBs tend to have a myriad of different components, the company can set unique process windows for each of the sensitive components even though they are on the same PCB. Not only does Krypton Solutions get measurements of the profile on select components for each PCB, but the KIC RPI also automatically charts the profile specs on basic SPC graphs, including process capability (Cpk) numbers. Suddenly, the company has access to real-time process information and trends that, in turn, allow it to make better decisions regarding how the thermal process is run. For example, Krypton Solutions no longer relies on automated optical inspection (AOI) or in-circuit test (ICT) to belatedly announce a problem — instead, out-of-spec situations are captured immediately. The company even has the potential to detect issues before they evolve into defects with a warning from the KIC RPI that the process is no longer in control. Its semiconductor and medical clients have critical and sometimes expensive PCBs assemblies that need to perform perfectly for years to come. These clients are now assured that their products are processed in spec, and Krypton Solutions has documentation to prove it.

Another challenging issue is that the company cannot sacrifice PCBs from repeated profile runs or mishaps in the oven. Its clients often request delivery of 100 percent of the assemblies; therefore, no scrap is permitted. The KIC Explorer with Auto-Focus enables the company to achieve that consistently. One example relates to the initial oven setup. For a PCB assembly not previously produced, the software recommends the oven recipe prior to running a single profile. Krypton Solutions’ experience is that this initial oven recipe gets it close to the optimal value while one or two subsequent profile runs will yield the optimized oven setup. There is little risk of damaging the PCB on the initial profile run. Using removable aluminum tape to attach the thermocouples (TC) on the initial profile run eliminates the need to sacrifice the PCB for initial oven setup.

Being a high-mix/low-volume CM means frequent oven setup for new assemblies. In the past, the company could spend up to a half day fine tuning the oven before starting the production run. Today, it is down to a couple of hours and expects to further reduce that time as it moves up the learning curve with the new tools. The fast setup time has been achieved through the accurate Auto-Focus prediction software that typically finds the best oven recipe within a couple of profile runs. The time consuming part of such fine tuning of the oven recipe is not the prediction part, which is performed within seconds, but rather is related to the time it takes the oven to stabilize on the new setting. Typically, oven zones can stabilize within a few minutes when the zone settings call for increased temperatures. Cooling the zones, however, may require 20-30 minutes or more. The trick is to avoid numerous “trial and error” reiterations, hence the importance of an accurate prediction software. This challenge is amplified when replacing older ovens with new ones or when expanding to additional production lines. The company can have up to 100 different recipes with associated PCB profiles stored in each oven. Utilizing the Auto-Focus simulation software has made transitioning these to a new oven manageable.

Conclusion

Krypton Solutions believes in using technology to provide a better solution to its demanding clients, while reducing the cost of production. It also strives to differentiate its company from other CMS organizations in this highly competitive market. One example of how this strategy plays out is represented by its investment in a real-time thermal process management system. The company realized that the reflow oven constituted a real challenge in terms of securing and documenting the requested PCB quality. The ultimate output from a reflow oven is to produce a PCB profile inside a specific process window, which is dictated by solder paste and component tolerances. Essentially, the reflow oven is a profile machine. The missing link in this profile machine is the measurement of the profile. By adding an automatic profiling system, the company no longer runs blind between spot checks and the production is no longer interrupted to perform such measurements manually. Additionally, the new window into the thermal process has enabled the company to optimize its thermal process with the end result being improved quality and productivity. This technology has enabled it to exceed demanding clients’ requests while running its operation more cost effectively. Krypton Solutions operates in a technology industry in a high-cost country. To succeed, it constantly must look for technologies that allow it to make smarter decisions in its factory in order to increase customer value.