ZF Microsystems, the inventor of the now standard PC/104 and 5 1/4-inch Single Board Computer concepts, is no stranger to setting precedents in the personal computer (PC) market. The company, based in Palo Alto, California, recently needed a strong, heat-resistant chip carrier that could be produced economically for its OEM module single-component computers.

To create the single surface-mount component carrier, ZF Microsystems enlisted the help of Phillips Plastics Corp., a custom injection molder located in Prescott, Wisconsin. Certified to ISO and QS-9000, Phillips Plastics is a custom injection molder of both plastic and metal, with annual sales approaching $200 million. The company provides contract manufacturing and assembly services to original equipment manufacturers (OEMs) in the automotive, medical, appliance, consumer electronics, and recreational markets.

Diverse Injection Molding Services

Phillips employs approximately 1800 people at 19 locations throughout the United States. Its manufacturing facilities make use of some 225 presses, ranging in size from seven to 750 tons. A wide range of specialty injection molding services are offered, from prototype and market-entry molding to low- and high-volume manufacturing. Specific molding capabilities include insert, multi-shot, and micro molding, magnesium injection molding, and metal injection molding.

Crystalline Polymer is Key

Reportedly, Phillips was able to dramatically reduce production costs of the chip carrier while meeting ZF Microsystems' stringent performance requirements. A major reason for the dual achievement was the firm's successful conversion from a competitive resin to the QUESTRA EA 513 crystalline polymer from Dow Plastics, Midland, Michigan.

According to Dow, the QUESTRA polymers are particularly well suited for electrical and electronic part applications. Printed circuit board (PCB) connectors, surface-mount connectors, coil bobbins, switches, and relays are counted among the applications for the resins, which are said to provide innovative options for product designers and manufacturers seeking a mix of value and performance properties in an engineering thermoplastic.

"To successfully manufacture the chip carrier, we needed a resin that was heat-resistant, flame-retardant, impact-resistant, and that had dimensional stability for this tight-tolerance application," said Steve Wolfe, materials engineer for Phillips Plastics. "We first experimented with liquid-crystal polymers (LCPs) for this application, but found that the resin was over-engineered and, more importantly, wouldn't fill the part," he explained.

Known to have an outstanding range of properties, liquid crystal polymers would normally be suitable for high-performance parts such as electronic connectors. The reason is that their ease of processing gives them the ability to fill long, narrow molds, according to Rosato's Plastics Encyclopedia and Dictionary.¹

But after finding the LCPs to be less than ideal for this application, Mr. Wolfe and his engineering team began searching for a more appropriate resin. They concluded that the Dow QUESTRA crystalline polymers would fit the specifications in more ways than one.

"We decided to drop QUESTRA polymers into the machine," said Mr. Wolfe. "With just a few minor adjustments, the resin filled the part, met all of the critical product guidelines and, ultimately, provided a significant cost savings," he explained.

Performance Benefits

By using QUESTRA polymers instead of LCP, Phillips was able to cut its resin cost by two-thirds. "Through the years, we have worked successfully with Dow Plastics on a variety of development projects," noted Mr. Wolfe. "Fortunately, in this situation, we were able to save time because we were doing unique on-site trials with the resin and had sufficient quantities of QUESTRA crystalline polymers on hand. Because it is so cost effective, we see the resin as a viable replacement in many applications using LCP," he stated.

QUESTRA crystalline polymers are manufactured using metallocene catalyst technology. The enhanced performance and technology benefits of the polymer are said to give OEMs, molders, and designers greater freedom in using plastics for demanding market applications.

"QUESTRA polymers offer an exciting combination of performance characteristics and competitive advantages, including increased productivity and profitability," said Karen Fennessey-Ketola, Dow market development manager. "With low specific gravity, QUESTRA crystalline polymers reduce the weight of material needed to produce the part and lower overall costs when compared to competitive resins, including LCP," she explained.

In addition to high-heat performance properties, the polymers are resistant to a broad range of chemicals, water and steam. They are said to have exceptional electrical properties and good stiffness, and their extremely low moisture absorption provides excellent dimensional stability.

Processing Advantages

According to Bill Burke, project manager, Dow Technical Service and Development, QUESTRA crystalline polymers easily fill complex and long flow- path tooling; they also permit the use of multi-cavity tools to increase output. Processing with the polymers can also reduce scrap and regrinding, contribute to shorter molding cycle times, and require lower injection pressure. This equates to less machine wear and lower maintenance costs, and minimizes warpage in the molded parts.

By using QUESTRA crystalline polymers, Phillips Plastics was able to mold ZF Microsystems' single surface-mount component carrier in a cost-effective manner.

"We are very pleased that we were able to successfully manufacture the chip carrier and meet all of our client's guidelines," Mr. Wolfe said. "QUESTRA polymers were very beneficial in producing a high-quality product that provided cost savings to us as well as to the client."

Mr. Wolfe added that because of the unique properties of the polymers, Phillips Plastics has also been successful specifying QUESTRA crystalline polymers in applications where nylon and PET have typically been used.

Dow Plastics is a business group of The Dow Chemical Company and its subsidiaries. The Dow Chemical Company is a global science and technology-based company that develops and manufactures a portfolio of chemicals, plastics, and agricultural products and services for customers in 168 countries around the world.

About Phillips Plastics

In addition to custom injection molding, Phillips Plastics offers capabilities in assembly, EMI/RFI shielding, stereolithography, and selective laser sintering. For EMI/RFI shielding, the company offers five processes: electroless plating, conductive paint, vacuum metalizing, embedded mesh, and conductive foil.

Phillips' micro molding operations provide high-volume, precision components weighing as little as two grams to 1.8 ounces, the company reports. Process controls are said to permit tolerances of +/- 0.001 inch or tighter, in fully automatic, high-speed presses under 30 tons.

*QUESTRA is a trademark of The Dow Chemical Company.

Reference

¹ Rosato, Dominick V. 1993. Rosato's Plastics Encyclopedia and Dictionary. Munich: Hanser Publishers, p. 415.

This technical information has been contributed by
Phillips Plastics Corp.

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