Page 60 Ensuring Success in
PCB Manufacturing and Assembly Continued from page 58
and SMT materials are quite small, so that it is impossible to follow the operation of these machines with the naked eye. Multiplied by the number of machines on a production floor and even the most experienced industrial engineer will have difficulty explaining sudden drops in performance or finding causes of unexpected quality issues. This not only affects the reliability of on-time
product delivery, but also stresses associated pro- duction resources and materials supply because they cannot be synchronized effectively with requirements. Execution of planning changes becomes risky because of all the unknowns related to physical commitments for products partially built, materials consumed, and spoilage. The true utilization of machines is also unknown since recent machines with multiple heads, multiple conveyors, and multiple modular stages can hide significant avoidable idle time. Also, timing of changeovers between products
cannot be predicted accurately, which can create operator resource bottlenecks. Reports created using data extracted from individual machines have little meaning, because they do not consider their environment, specifically the effects of external causes of stoppages.
Advanced Capabilities Fortunately, availability of advanced capabil-
ities is creating new approaches that can collect and process data in real time no matter what the SMT machine vendor or related process may be, including manual operations. Events and support- ing data are read and normalized, eliminating dif- ferences in data format and creating a single com- mon language. Collected data is automatically qualified. For example, when a machine stops, the production line can be analyzed to see why the flow of PCBs has stopped, or why the output conveyor is blocked. In this way, any event occurring on the production line can be understood and processed.
Information about complex SMT processes is recorded, such as the under-utilization of modules or heads, which exposes areas for productivity enhancement. Event data collected even includes the precise usage and spoilage of materials so that accurate material consumption can be reported. By collecting and processing data in real time,
it can be used to benefit production. For example, it can be used for asset management to increase pro- ductivity. It can be applied to material management for just-in-time delivery of materials to a line. This
leads to an increase in productivity, improved relia- bility for on-time delivery, reduced on-site finished goods storage, and better execution of changes to meet customer requirements. The follow-up article in this two-part series will review the remaining steps required for cost-effective and high-quality PCB manufacturing and assembly. Contact: Mentor Graphics Corp.. 8005 SW
Boeckman Road, Wilsonville, OR 97070 % 800-592-2210 or 503-685-7000 E-mail:
sales@mentor.com Web:
www.mentor.com r
EMI Shielding Caulk Cures Quickly and Is Paintable
Continued from previous page
faces in a manner resembling their actual intended application and were then painted with the MIL- PRF-22750 epoxy coating on only one side. Test specimens for each compound were then exposed to three rounds of salt fog (166, 500, and 1000 total hours) with the results showing all four of the trial materials performed far better than the Ag/Cu con- trol, especially in the unpainted sections of the panels. Other than traces of surface oxidation, there were no signs of corrosion on the trial mate- rials while the control had clear signs of galvanic corrosion even through the polysulfide environ- mental seal. Other specimens with the same compounds
were exposed to thermal cycling (–57 to +157°F/–49.5 to +69.4°C) and then underwent wet and dry tape adhesion and flexibility testing. All of the compounds showed adequate adhesion and flexibility except for the Ni PTE control, with poor adhesion of the MIL-PRF-22750 coating. Since the Ni PTE control was found unsuitable for all appli- cations requiring the adhesion of an epoxy coating, it was removed from further testing. Each SE test panel was 26 x 26 x 0.25-in. (660
x 660 x 6.35mm) with a 0.375-in. (9.53mm) through- slot down the middle. The SE panels were mounted to the wall of the Chomerics SE test chamber and attenuation measurements were taken before and after the slots were filled with the conductive com- pounds and painted. The panels were then exposed to thermal cycling (–57 to +157°F/–49.5 to +69.4°C). SE tests were performed and followed by three rounds of salt fog (166, 500, and 1000 hours total). The results showed the Ag/Al PU to have poor shield- ing even before thermal cycling and the Ni/Al PU lost its shielding ability after 500 hours of salt fog. The Ni/C PTE compound retained adequate shielding throughout and the Ag/Al PTE was exceptional throughout compared to the remaining Ag/Cu sili- cone control compound.
Physical Tests Physical tests included lap shear according to
ASTM C961, hardness according to ASTM C661, and change in flow rate over time for the uncured compounds according to ASTM C603. Results showed the cured PTE trial materials to be stronger and harder than the control while retain- ing good workability.
Continued on page 65
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July, 2015
Aven Tailors Inspection Systems For The Perfect Fit
Tailor Your Own System at
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