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www.us-tech.com Production
High-Rel Assembly Reclamation: Securing Waste for Greatest Return
By Mitch Holtzer, Director of Reclamation, Alpha Assembly Solutions
quantity of defective circuit boards, such as those destined for an aircraft cock- pit, assemblers must consider how the value of the substrate and components can be recovered without compromising a top-secret circuit design. Keeping the scrapped materials in the U.S. is an obvious first principle.
M
Selling the scrap to a broker or dealer could easily result in the boards being shipped to a foreign country for disassembly or disposal. This outcome needs to be prevented at all costs. To do so, the assemblies must be destroyed by an ITAR-certified service
provider or recycler. This certification guarantees that the scrap boards do not leave the U.S. It also ensures that the service provider’s business practices have stood up to a high level of government scrutiny. Another consideration is the reclamation method itself. Economic circuit
destruction could be accomplished in one of two ways: incineration or granu- lation, followed by metal recovery. Both methods effectively secure the intel- lectual property of the design, which is of critical importance for military and aerospace applications.
Incinerate or Granulate? While inexpensive, incineration makes the metal recovery process more
difficult. A hot enough flame oxidizes valuable base metals, such as copper and tin. Once oxidized, a chemical or electrochemical process must be used to make the tin and copper reusable. The additional process work involved makes this the unpopular option. The second method is granulation. In this process, a mill is used to grind
or crush circuits into a powder-like intermediate. This process has several ad- vantages. Granulation doesn’t need to take into account the design of the cir- cuit or the identity of the components. Once granulated, calculating the value of this powder is very straightforward. The weight percentages of the base and precious metals, such as gold,
platinum, silver, and palladium, can be measured easily, offering a clear determination of the value recovered from the scrapped as- semblies.
Another source of recyclable
scrap and waste from the produc- tion of military and aerospace elec- tronic circuit assemblies is the sol- der paste that remains on a stencil when production switches from one assem- bly to another. The paste bead diameter on the last assembly produced needs to be very
Granulating scrap PCBs is an quick and easy way to break down and measure the base and precious metals that make up an assembly.
similar to the bead diameter used on the first assembly. The most common process recommendation is between 1.5 and 2 cm (0.6 and 0.8 in.) to reduce defects. When a different assembly begins production on an SMT line, obvi- ously the stencil will need to be changed. The solder paste left on the previous stencil must be routed to an appropriate reclaim container.
Flux Drift During the course of its use, solder paste’s ratio of metal to flux increas-
es, as paste flux is selectively transferred through a stencil aperture at a high- er rate than solder powder. This phenomenon is referred to as flux drift. If the used paste, subjected
to flux drift, is mixed with fresh paste, the resulting inhomogeneous concoc- tion will be subject to process variation. Anyone familiar with Six Sigma prin- ciples will recognize that process variation can lead to defects, which then adds to the scrap heap. The cost of producing advanced military or aerospace assemblies is high-
ly dependent on first-pass yield. When considering the risk of repairing an as- sembly designed for use in a demanding mission-critical or life-saving appli- cation, high reliability far outweighs the saving of a flawed circuit. And, when scrapping such sensitive materials with design intellectual
property that can compromise national security, one must enlist an ITAR-cer- tified service provider to ensure scrap boards do not leave the United States. Minimizing losses by obtaining the highest return on scrapped assem-
blies and unusable solder paste should be a main consideration for military and aerospace circuit assemblers. In the high-reliability sector, waste recla-
mation presents a huge opportunity for savings. Contact: Alpha Assembly Solutions, 300 Atrium Drive, Somerset, NJ
08873 % 908-791-3045 E-mail:
laurie.kneller@
alphaassembly.com Web:
www.alphaassembly.com r
inimizing the scrap and waste from electronic assemblies is a top pri- ority for the military and aerospace sectors, where high-reliability is of utmost importance. However, once the decision is made to scrap a
June, 2017
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