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www.us-tech.com
June, 2017 Developments in Rapid Electronic Assembly By Stanley L. Bentley, P.E., Senior Technical Advisor, RapidProto
Systems, Inc. Unlike its mechanical counterpart, RPT is not a “click-and-squirt” process, and can have capital equipment costs as low as $1,000. The general definition of RPT is to have parts, PCB and assembly out the door within three working days of receipt of files.
R
apid electronic assembly, or RPT (rapid pro- totyping) for short, was introduced around 1995 as a standalone service by Diversified
part shapes for programming. The early system used a database obtained from the major electron- ic distributors to compare against the BOM for partial matches that could then be researched for complete part numbers and part shapes. The man- ual part of the task was sent to a dedicated engi- neering team in India for final clean up during off- hours in the U.S. Process tracking was achieved with use of
project tags affixed to the traveler and then locat- ed in each process area and available to the project manager in real time. This patented process tracked the time in every work center and alerted the project manager of any delays. The system included a full-duplex voice communication with every process area that could be activated by high- lighting the specific order on the computer screen. Internet-accessible project cost and time esti-
Selective solder systems can eliminate the need for hand soldering.
Several innovations came from Diversified
Systems’ early offering, including Internet sourc- ing, BOM scrubbing, and real-time process track- ing, as well as online project costing, scheduling and time estimation.
RPT’s Early Days The Internet of that era was not fully imple-
mented. What was used was a program running an early database from Micro Database Systems of Lafayette, Indiana, (a precursor to Microsoft’s SQL) with modem links to a major electronic dis- tributor’s data base of components. This was later rolled into a startup called Digital Market, which later became Agile Software. This crude imple- mentation emulated today’s cloud servers. BOM scrubbing remains a major hurdle in getting the parts identified for procurement and
mation was accomplished by two patented pro- grams that customers could access through the internet. The programs provided information about the PCB and assembly cost as the customer entered specific data about the design. These pro- grams allowed the designer to make technology decisions without requiring assistance from a PCB fabricator or assembler. The cost model depended on the activity-based cost system of the RPT serv- ice. Program managers also accessed the software to estimate total project cost for production as well as prototype. Today, rapid prototyping is mostly associated
with mechanical items. Inexpensive printers are available to make plastic parts from a 3D CAD file. This technology has biased the general market’s opinion of how quickly a PCB or PCB assembly can be obtained. While the technology certainly exists, the
inks to replace copper do not. Copper has a unique combination of electrical and thermal conductivity. It can carry large amounts of current to the load and it can efficiently remove heat from critical components. Until a viable replacement for copper can be formulated, the fabrication process of the
PCB will remain fairly long, and will involve a lengthy list of process operations, including drilling, imaging, plating, laminating, solder masking, and surface finishing. Higher technologies, such as blind and buried
or stacked vias, can double or triple the process time. The PCB remains the longest lead item in a rapid prototype. Even if they are made in-house, the process time for a complex PCB (not double-sided or 4L) is three to five days. The process time of a high- tech PCB puts you outside of the definition of RPT.
Current PCB Fabrication The PCB fabrication process is serial and
sequential. There are no parallel operations. The major processes are even located in different departments and separated by walls. A common
A flying probe tester measures opens and shorts against the design net list.
reference in the fabrication industry is that “PCB departments can’t breathe each other’s air.” For example, you cannot put a complex CNC
drilling machine in an acid plating area, or a dusty router in an imaging area where you are putting a trace and a space less than a single hair’s width apart. Further, the process is not like a merry-go- round where you can enter and exit at any time. The process has a defined start, and moves from
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