High-Speed Sawing with a Micro Slicing System
Development engineers at Philips' Center for Manufacturing Technology (CFT), Eindhoven, the Netherlands, were faced with the daunting task of delivering a high-speed ceramic diode sawing process to their Manila, Philippines, factory within 12 weeks. Adding to CFT's technical challenge, delivery of the sawing process had to be timed with the introduction of a new reel-to-reel production line. Deliverables included doubling the output of an existing sawing process that already incorporated 50 diamond blades on a gang arbor, parts handling, high-speed wax bonding and cut parts cleaning.
Raymond van As, project engineer for Philips' CFT group, knew that no matter the sophistication of his analytical tools or test methods used to achieve a Six Sigma-capable sawing process, he would need a more superior machine than the existing sawing equipment at the company's Manila factory. "The Manila factory's sawing machines were already operating at levels beyond their normal capacity. We needed more power from the saw," he explains.
Existing Separation TechnologyProduction volumes at Philips Semiconductors Philippines Inc.'s (PSPI) Manila factory remained at a steady 500 million SOD110 surface mount packages annually. SOD, which stands for standard outline diode, is a new type of ceramic surface mount device (SMD) diode package.
The SOD110 high-performance package uses Philips' proprietary V-packTM technology and outperforms both mini-MELF glass and plastic-packaged MELF products. The SOD110's rectangular-shaped, stress-free ceramic package is easier to handle than cylindrical MELFs, contributing to its superior pick-and-place performance and reliability during mass board assembly. As a result, the product is in high demand.
CFT originally designed and delivered to the Manila factory a volume sawing process that consisted of 50 ceramic bars precisely mounted to a two-sided frame or loading rack, with each bar containing 149 products. Typical dimensions of the separated products are 1.50 x 1.25 x 2.20 mm. Philips' unique cutting approach consisted of 50 diamond blades and adjoining pitch spacing components precisely assembled on a gang arbor. After only three passes of the gang, the sawing process was complete, yielding a total 7450 products per load run.
According to Jimmy Bonifacio, manager of process engineering at PSPI, throughput at the Manila factory was only limited by the existing saws' inability to withstand increased cutting load conditions when attempting higher feed rates. "We were experiencing a bottleneck in our gang sawing process. We knew we could easily invest in a new machine, but we also wanted to innovate the process by improving cutting efficiency. We needed a cutting-edge technology to achieve this," he says.
Design ApproachCFT used an Integral Process Development (IPD) method (see Figure 1) and design of experiments (DoE) tools to ensure on-time delivery of a new sawing process. By applying a risk matrix to existing saws at the Manila factory, CFT engineers realized that for a new high-speed sawing process to be a technically and economically feasible alternative, the cutting system would need greater spindle power, improved structural stability and rigidity, and an indexing accuracy commensurate with Philips' Six Sigma quality program. After evaluating the various options on the market, the engineers decided to add Veeco's MSS-816 micro slicing system to their development lab.
The micro slicing system uses ultra-high precision, anti-friction linear bearings for all three axes of travel. Indexing accuracy is up to ñ0.00001 in. (ñ0.25 æm), which is consistent with Philips' minimum 1.33 Cpk process capability requirement.
The system's bridge-type construction and a base made of heavily ribbed cast iron provided the stability and rigidity the CFT engineers were looking for. The precision-feed X-slide and the indexing Y-slide mounted on a 5500-lb (2500-Kg) laboratory-grade granite block and kinematically suspended on three-point adjustable supports ensured distortion-free alignment of the datum plane in relation to the spindle and Z-axis.
These structural features would ultimately prove beneficial to eliminating side loading of the blades at the higher table feed rates desired for the high-speed sawing process. According to CFT engineers, the stiffness of the micro slicing system's dual-supported 10 hp mechanical bearing spindle arrangement, along with the machine's reliability and fixed tabletop in relation to the spindle system, were the key features that led them to select the system.
"The system was the perfect fit of process to equipment," says van As.
CFT DeliverablesDuring the technical feasibility phase of development, CFT engineers documented a detailed flow analysis of the complete handling, sawing and cleaning processes, in addition to the results of the risk matrix, in a technical feasibility report.
As CFT launched into the alpha phase of the IPD, it was readily apparent to the engineers assigned to the project that many of the risks identified in the feasibility phase were minimized or eliminated with the implementation of the micro slicing system. Product cost reduction ideas, such as saving material cost by increasing the number of products per ceramic bar from 150 to 175, were added to the deliverables. CFT immediately set out to develop a custom blade type that would:
- Tolerate a narrower kerf size without compromising cut geometry and part tolerance
- Increase useful blade life
- Result in substantially higher table feed rates
Results of the New SystemThe beta phase of the IPD concluded with the final design and testing of the sawing process, related equipment and tooling prior to the transfer of the complete sawing process to the Manila factory. Within two weeks after installation of the micro slicing system and training of local engineers, the high-speed sawing process was officially released for mass production.
Results of CFT's development work and selection of the micro slicing system proved highly successful and yielded the following improvements at the Manila factory:
- Output of the high-speed sawing process achieved production levels of 1.5 billion SOD110 diodes per year, effectively increasing production capacity by a factor of 2.4 over the old sawing process and equipment set
- Increasing the number of products per ceramic bar from 150 to 175 decreased the percentage of the separation process to the factory sales price (FSP) from 38% to 4%, thereby reducing the fabrication cost of the SOD110 diode by a factor of 10 (see Figure 2)
- Due to the structural integrity of the machine, the frequency of blade changeover and blade dressing (resharpening) was reduced to once a week instead of every four hours, thereby reducing labor requirements and downtime.
Author's AcknowledgementsI wish to thank Raymond van As and F.H. in't Veld of Philips CFT Eindhoven, the Netherlands, Rey H. Capinianes, Director, BFG-GA, and Jimmy D. Bonifacio, Philips Semiconductor Philippines Inc., for their cooperation and the technical data and SOD110 product information found in this article.
Editor's note: Veeco Instruments Inc. acquired Manufacturing Technology Inc. (MTI) in October 2004, and is now called Veeco Slider Process Equipment Inc.
For more information about the micro slicing system, contact Veeco Slider Process Equipment Inc. at 2226 Goodyear Ave., Ventura, CA 93003-7750; (805) 644-9681; fax (805) 644-3541; e-mail firstname.lastname@example.org ; or visit http://www.veeco.com .
More information about Philips Semiconductors can be found at http://www.semiconductors.philips.com .