Circuits Assembly - July 2008 - (Page 39)

PWB Rework is added. The web circuits are fabricated and applied to the board. Circuits are aligned to the isolation layer using registration pads created from the PWB Gerber file and based on the size and shape of nearby lands, “so that when it’s optically aligned, we know all the circuits line up,” DesMarais says. Once the circuit is registered atop the B-stage isolation layer, the board is exposed to a mild lamination process, involving sufficient heat, time and pressure to partially cure the material and flatten the circuit, with the epoxy adding adhesion. At this stage the actual cure is about 45%. The material – a one-part epoxy with insulation resistance of about 1000 volts per mil – serves as an insulating layer. The temperature of the board itself never rises above 280°F, and is heated only for a few seconds in order to limit the thermal excursions. Next, paste is either dispensed or printed, and the pads and terminations are then touch-soldered. Soldering is performed with an iron, although Additive is studying the use of automated soldering equipment. The solder used matches the customer’s specifications. Inspection is performed using a video inspection system, and continuity test is conducted on all etch cuts, and “anything nearby,” including innerlayers. The final step involves a line solder mask, which is heated at 275°F for 45 minutes – about 80% of the necessary cure and well past the point of tackiness. (The remaining polymerization will occur during assembly.) Final PWB finishes can range from OSP to gold, HASL, or immersion silver or tin. The entire process meets RoHS requirements, DesMarais says. “Everything we use is compatible. In our RFQ, for example, we ask about the solder paste, and use the same or a compatible version in order to meet the requirement.” And aesthetically, the ECOs to the reworked boards are hard to detect (Figure 1). Additive is gaining traction with EMS companies looking to expedite time-to-market or where re-spinning can’t occur, such as with continuous flow manufacturing, he says. “You could redesign and wait and spend and wait and spend,” says DesMarais. Web circuits can resolve electrical performance issues, such as when a known or predictable electrical performance is needed that other alternatives would not resolve. For instance, he says, “when your application calls for timing – jumper wires won’t do that; and polymer ink is limited in terms of surface finish, and is lead-containing.” Web circuits also have been used where wires can’t go, for example, under a BGA and connecting to microvias. Another use is inventory control. Today, Additive has capacity to rework orders “from a single board to the tens of thousands” of boards using the web circuit process, DesMarais says. Down the road, Additive’s business model calls for a number of “completion centers” located in strategic spots around the world. Using overnight couriers like DHL, DesMarais says, “We can put up to 500 web circuits in a letter pack and ship them anywhere.” The completion centers would be staffed with a handful of employees who would perform final assembly and delivery. DesMarais envisions centers along the Mexican border, in Eastern Europe, the AsiaPacific and South America. The web circuit technology would remain in the US, he says. However, the CAD files could be sent to the centers so tooling could begin immediately. And thus, Additive’s web circuit technology would truly envelop the globe. n Mike Buetow is editor in chief of CirCuits Assembly; mbuetow@upmediagroup.com. LEADING PB-FREE SOLUTIONS FROM JAPAN Seika Machinery provides the North American market a line of advanced SMT and ATE machinery combined with world-class sales, service and support. Find out why Seika’s SMT product line has earned a higher sales volume and share of market in Japan. YOUNG JIN PCB HANDLING SYSTEMS Key Features • Industry first and patented magnetic roller mechanism eliminates the use of pusher which causes stress on PCB's during transfer • NG stocker can be linked with AOI/SPI via RS232C • Safety covers with interlocked doors • User friendly touch panel operation • Customized systems available HIROX DIGITAL MICROSCOPE SYSTEM Key Features • Inspect objects dynamically in 360 degrees with patented Hirox design • Superior BGA inspection capable of up to 200x magnification. Low maintenance costs achieved with use of spring loaded lens tip to protect samples. • Highly configurable and flexible lineup of lenses and peripheral devices • Optimal illumination using metal halide lamp for balanced color spectrum • A multitude of 2D/3D profiling features available for a wide range of applications • Customization available for tailoring to client-specific needs CALL TODAY! SEIKA Seika Machinery, Inc. 3528 Torrance Blvd, Suite 100 Torrance, CA 90503 Ph: 310-540-7310 Fax: 310-540-7930 Email: info@seikausa.com Visit the full product line at Figure 2. … Through-hole and microvias … circuitsassembly.com Figure 3. … And resolve timing and other electrical issues that jumper wires cannot. www.seikausa.com Circuits Assembly JULY 2008 39 http://www.seikausa.com http://www.seikausa.com http://circuitsassembly.com

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Circuits Assembly - July 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Focus on Business Global Sourcing On the Forefront Screen Printing Tech Tips Will Electronics Follow the Sun? ‘Warm’ Manufacturing Heats Up Reputation Trumps Recession, China ‘Web Circuits’ A Novel Non-VOC Conformal Coating Krypton: Benchmarking Customer Satisfaction 2008-09 CIRCUITS ASSEMBLY Buyers Guide Wave Soldering Pb-Free Lessons Learned Process Doctor Materials World SMTA Int'l Product Preview Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - July 2008

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