Materials Expertise Enhances Firm's Precision Machining Services

High-Performance Engineering Plastics Are the Specialty of a Precision Machining and Fabricating Firm that Serves the Medical, Semiconductor, and Aerospace Industries

By Mark Shortt
Editorial Director, Design-2-Part Magazine

Finding the right material for the right job is essential in the medical industry, where the high temperatures and pressures of autoclaving rule out the use of conventional plastics in products that require repeated sterilization. One company with a skill set that matches the often urgent need to "find the right material" is Piper Plastics, Inc., a diversified manufacturer of precision plastic and metal parts and assemblies for multiple markets. In business since 1980, Piper Plastics offers expertise in material selection and engineering/design assistance. Both are key components of the "total package" customer service philosophy that supports the precision machining and fabrication services offered by Piper at its two domestic facilities in Chandler, Arizona, and Libertyville, Illinois.

"Piper Plastics works with all materials, metal and plastic," says Ryan Close, the firm's sales manager. "Our focus and expertise is with high-performance engineering plastics that can withstand extreme temperatures and chemical composition. We will provide help on the correct material selection for the application. We will machine or mold the parts, and assemble the parts in our cleanroom. We help every step of the way from beginning to end."

Comprehensive Services

Piper Plastics applies its materials knowledge directly to the precision machining and fabrication of plastic and metal parts for the medical, semiconductor, aerospace, automotive, biotech, food processing and packaging, and oil industries. Its manufacturing capabilities include a comprehensive offering of horizontal and vertical CNC machining, CNC turning, routing, and drilling; automatic screw machining, and secondary annealing. For medical applications, the company employs what it calls "unique specialized annealing and machining processes" to produce lower-stress parts that stand up to repeated autoclaving and sterilization. Parts that are manufactured using these proprietary processes are said to exhibit higher chemical resistance and increased stability following repeated autoclaving and sterilization cycles.

"We have state-of-the-art equipment to manufacture an array of tight-tolerance parts," says Close. "By better understanding material stress, Piper Plastics is able to produce parts more accurately with less material waste and improved part performance. Piper can achieve mirror finishes on parts, along with holding tolerances to ± 0.0004-inch."

The company's development of a new molding technique has opened up a new range of intriguing possibilities for parts manufacturing, according to Close. "Our proprietary molding process allows us to produce thick cross sections (thicker than 1/4-inch) with superior properties and low porosity," he says. "It is ideally suited to making large, irregularly shaped parts out of expensive materials. The end results are reduced waste, better yield, and better material performance."

For fabrication and assembly, Piper Plastics utilizes techniques such as ultrasonic welding, fusion welding, ultrasonic insertion of metal inserts, and hot air welding. Chemical bonding and thermal diffusion bonding of plastic materials are also offered, along with thermoforming, finishing, cleaning, packaging, and assembly. In addition to its two domestic facilities, the company operates a low-cost manufacturing facility in Asia. "We can do all R&D and low-quantity orders domestically in the U.S. and move the production to our low-cost region to help reduce costs," says Close.

According to the company, the assistance that its personnel provide in selecting the right material for a specific application is an integral part of the firm's customer service function. Trained specifically to assist in this area, Piper's personnel can draw from an extensive inventory of high-quality plastics to recommend alternative, cost-effective materials where appropriate to help solve technical challenges. Available in sheet, rod, tube, and film, these materials can be injection molded to near net shape. They can also be extruded, compression molded, or thermoformed.

Another key part of the firm's customer service philosophy is the design and engineering assistance that it offers at little or no charge. A full-time design engineering staff enables Piper Plastics to provide a full analysis of its customer's designs. Piper's experienced engineers offer reviews of customers' designs for material selection, part performance requirements, manufacturability, and cost-effective production.

Piper Plastics serves all areas of the aerospace and defense industries, specializing in tight-tolerance machined parts on assemblies. The company manufactures precision-machined plastic and metal parts for engines, satellites, and missile systems, as well as parts for fuel cells, safety apparatuses, seat belt enclosures, and missile nose cones. According to Piper, it is "qualified to produce highly complex parts and assemblies that require a high level of accountability and performance."

The company maintains a vast supply of plastic materials, ranging from ABS and acetal, to FRP panels, GE Ultem®, DuPont Delrin®, Mylar®, and Vespel®, and Victrex® PEEK^TM, including the glass-filled version. Piper Plastics has had considerable success in molding Victrex PEEK, a high-performance thermoplastic with a unique combination of exceptionally high strength, high temperature resistance, and excellent chemical resistance at elevated temperatures. The material has a continuous service temperature of up to 260°C (500°F), showing excellent retention of electrical and mechanical properties. Reinforced grades are said to attain a heat deflection temperature (HDT) of 315°C.

A semi-crystalline material, Victrex PEEK is insoluble in most common solvents and very resistant to a wide range of organic and inorganic liquids at high temperatures. In steam or high-pressure water environments where temperatures exceed 250°C (482°F), PEEK reportedly can be used without significant degradation in properties. Its resistance to gamma radiation is said to be exceptional at high dose levels.

Microprocessor Test Sockets Are Molded, Machined from Ceramic-Filled Polymer

For more than 20 years, Piper Plastics has been a source of parts for makers of semiconductor manufacturing equipment. The company supports some of the major OEMs in the semiconductor equipment industry by machining and fabricating custom parts used in etching, lithography, CMP, final testing, wafer handling, and R&D applications. In addition to producing sockets, nests, and contactors, Piper Plastics manufactures high-quality parts for wet bench assemblies, chemical delivery systems, and polypro carts and cabinetry.

In the semiconductor industry, the demand for smaller, tight-tolerance IC packages that operate at higher frequencies is challenging the use of materials that have traditionally been specified for microprocessor test socket applications. Piper Plastics believes that it has obtained a competitive advantage by manufacturing high-performance test socket components from a ceramic-filled Victrex®, PEEK^TM polymer. The new components, designated EPM-2204U-W, are reportedly beneficial in key microprocessor test socket applications due to their significantly lower absorption of moisture and tight-tolerance machining. Test sockets are used in the final stage of the semiconductor manufacturing process, where the microprocessor chips are plugged into a circuit board for various system function tests.

"Because these chips have hundreds of metal contacts inserted into a single socket over 100,000 times, dimensional stability is critical in making sure the metal contactors are aligned correctly with the circuit board," says Dave Wilkinson, materials engineering manager at Piper Plastics. "A ceramic-filled VICTREX PEEK polymer has excellent dimensional stability and tolerance control across a broad range of temperature and humidity conditions."

Ceramic-filled VICTREX PEEK polymers are noted for maintaining impact strength, stiffness, and minimum levels of creep. An inherently pure polymer, VICTREX PEEK has greater hydrolytic stability than traditional test socket materials such as polyamideimide (PAI) and other imidized polymers. Versus ceramics, the filled VICTREX PEEK polymer reportedly offers half the weight and greater impact resistance and toughness. It is also said to provide superior processability and wear performance, along with favorable dielectric properties for insulative applications.

"We machine test socket components from blanks that we mold using a ceramic-filled VICTREX PEEK polymer," said Wilkinson. "We like the polymer's excellent machinability for tighter pitch and fine-diameter holes. Our tight-tolerance machining and near-net injection molding capabilities lend themselves very well to this new ceramic-filled polymer."

High-Temperature Polymer Meets Molding Requirements for End Effector Pads

Another project for the semiconductor manufacturing industry had the company injection molding end effector pads. To meet requirements for a material with higher strength and temperature resistance, Piper chose a proprietary blended VICTREX® T-Series grade polymer based on VICTREX® PEEK^TM and Celazole® polybenzimidazole (PBI). The melt-processable VICTREX T-Series polymers are designed to perform in "the most demanding" high-temperature applications requiring superior strength, wear, and hardness, as well as improved creep and thermal properties, according to Victrex plc, the manufacturer of the materials.

End effectors are typically made of metal; they function as the "hands" of a robotic arm, picking up the silicon wafers and moving them from one operation to the next. Pads are inserted onto the tips of the end effectors and act as "fingers" to grip and touch the wafer as it moves through the semiconductor manufacturing process. When choosing the pad material, Piper Plastics needed an ultra high-purity material capable of withstanding high temperatures in the range of 300°C (572°F).

According to its manufacturer, the thermally stable VICTREX T-Series polymer provides excellent mechanical performance at temperatures up to 300°C, as well as "excellent resistance to a range of extreme environments that degrade most plastics." Parts that are molded using the polymer exhibit outstanding chemical resistance and retention of properties, even after extended exposures to organic chemicals in high-temperature environments. Piper Plastics chose the material because, in addition to its high temperature capabilities, it is inherently lubricious and has a very smooth surface finish. Since the firm began using the VICTREX T-Series polymer, the lifespan of its end effector pads has more than doubled.

"VICTREX T-Series polymers have one of the best overall property profiles of any high-performance material," said Wilkinson. "They are the unique solution for applications requiring superior high-temperature resistance, unparalleled compressive strength, excellent tensile and flexural strength, and low fatigue properties - all with the cost-effectiveness of a melt-processable polymer."

VICTREX® is a registered trademark of Victrex Manufacturing Limited. PEEK^TM is a trademark of Victrex plc.

Celazole® is a registered trademark of PBI Performance Products, Inc.