Case Study— When sacrificing PCBs for the initial production run is not an option Case Study—
When sacrificing PCBs for the initial production run is not an option
SisTech Manufacturing is a small electronics manufac- turing services (EMS) company located in Bend, Oregon. The owner, Brad Kennedy, started the company in 2009 after a long career as an executive with larger OEM manufacturers. He founded SisTech Manufacturing to primarily focus on complex assemblies in high-mix, small- to medium-volume production. The facility pro- vides prototype assembly from a very few units up to production runs of 1000. In a typical week, the facility manufactures 7-10 new or different assemblies, both for leaded and lead-free electronics.
Mr. Kennedy was familiar with traditional profilers but felt that they did not accom- modate his needs. SisTech Manufacturing frequently does not have the luxury of sacrificing a single PCB for profiling pur- poses, nor can it scrap boards due to wrong reflow oven settings. Many assemblies are expensive and complex, with thousands of components and a dozen or more BGAs, including µBGAs. For example, a client may provide the BOM for three prototype assemblies and request three fully func- tional products. Te company needed a tool that could identify the correct oven recipe ahead of time. SisTech Manufacturing invested in a thermal profiler and
new generation of
process simulation soſtware. Te unique- ness of this technology is that every time a profile is run, the soſtware gets smarter. It learns the properties of the reflow oven as it relates to different types of PCB assemblies and process windows. Profile data accumu- lates in the soſtware’s database and, within a short period of time, the soſtware sug- gests the appropriate oven recipe for a new assembly without needing to run a single profile. Now when SisTech Manufacturing receives an order to build a new PCB assembly, the operator simply plugs in the
PCB’s length, width and weight as well as the appropriate process window. Te soſt- ware retrieves the previously run PCB and process windows that most closely resem- ble the new one. It then automatically kicks off a process optimization program that, within seconds, identifies what it believes to be the best oven recipe for this assembly. Mr. Kennedy knows from his previ-
ous manufacturing experience that there is a tendency to run very hot profiles on new products to secure adequate reflow. Tis inclination risks damaging the assembly by overcooking sensitive com- ponents or discoloring the PCB. Because this is completely unacceptable to SisTech Manufacturing and its clients, significant attention was paid to the results of the KIC Auto-Focus “first guess” profile. Te PCB assembly was checked visually with AOI and/or x-ray post-reflow, and zero reflow- related defects were found. Te real test, however, is the client. Aſter a year’s worth of experience with the system, SisTech Manufacturing has never received a reject from its clients for a product defect related to the thermal process. Tese clients are very conscious regarding product defects and reliability. Tey include both military and telecom companies,
in addition to 64 – Global SMT & Packaging – February 2011
www.globalsmt.net
more mainstream electronics. When there is an opportunity to profile
the PCB during a production run, SisTech Manufacturing will do so both to verify that the profile is in spec and to drive it deeper in spec with the process optimi- zation soſtware that can suggest further improvements to the oven recipe settings. Much of the electronics assembly
in the Western world today is flexible and characterized by high-mix,
low- to
medium-volumes. Te majority of the production also is of complex, critical and sometimes expensive assemblies. Te traditional method of soldering thermo- couples to the PCB for profiling as well as a “trial and error” method of relow oven setup frequently is unacceptable. SisTech Manufacturing has been successful with process optimization soſtware that offers reliable “first guess” oven recipe settings without needing to run a profile. It is still a guessing game, but the game is now played in a scientific way that takes advantage of the power of computers. Te old hit-and- miss approach is being replaced by modern technology that leads to better product quality, a more profitable operation and happier clients.
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