Pyralux® for Disk Drive Flex Circuit Designs

Effective design and use of flex circuit rigidizers is an integral part of the disk drive manufacturing process

The challenge faced by flex circuit designers and assemblers is how to fabricate and assemble the tiny flex circuits needed to make small drives reliably function at a high level of quality and efficiency.

Challenge: Reduce the size and assembly costs of disk drives to support the demand for substantially increased memory in portable devices

Solution: DuPont™ Pyralux® FR – High productivity, clean and precise circuit rigidizers / stiffeners simplify the disk drive flex circuit design and assembly process

Application Description

The use of portable electronic devices is rapidly expanding and the integration of digital audio and video entertainment into these devices is becoming commonplace. More, and more efficient memory storage and retrieval is in some instances becoming the limiting factor. Hard disk drives are outstanding memory storage devices but their size has limited their ability to be a useful technology for portable devices. To try and get around this barrier, "micro" drives are being designed that approach the size of a quarter.

Flex circuits play an integral part in the successful operation of reliable disk drives. The new challenge faced by flex circuit designers and assemblers is how to fabricate and assemble tiny flex circuits needed to make these small drives function to the same level of quality and efficiency as they do today.

Materials Selected and Why

While it may not be apparent when looking at the final assembly, the effective design and use of flex circuit rigidizers is an integral part of the disk drive manufacturing process. Precision formation and placement and overall processing latitude of circuit rigidizers can be the key to keeping overall yields and costs at the target levels. Use of inherently clean / low out-gassing materials as well as materials that can withstand rigorous cleaning processes after component assembly is also essential for long term reliability.

DuPont™ Pyralux® FR acrylic adhesive coated onto 3 and 5 mil thick DuPont™ Kapton®  film has a long history of being a very effective circuit rigidizer in disk drive applications. The Kapton® base film can easily and cleanly be punched or routed into the required shapes. It leaves no fibers or other stray particles that can later interfere with the smooth operation of the drive. The  thermal stability of Kapton® means it will not warp or twist during the component attach process. The ability to position it precisely where rigidizing is needed means that during final forming the circuit will fold exactly where intended. These attributes translate into low cost, high productivity assembly.

The FR adhesive is also particularly well suited for stiffener attach. FR has passed all industry out-gassing and ionic cleanliness requirements. In addition, its outstanding peel strength and resistance to attack by aggressive cleaning processes (hurricane wash) means that once attached, the rigidizer will stay attached throughout subsequent processing steps. As an acrylic based adhesive if re-work of some sort is necessary the adhesives can withstand multiple thermal exposures without degrading. These attributes mean high assembly yield, which translates into lower overall costs, and the overall cleanliness means no long-term reliability issues.

Bottom line, stiffeners made from DuPont™ Kapton® and DuPont™ Pyralux® FR can easily be formed and placed where they need to go, they stay in place during further processing steps and they do not detract from the performance of the disk drive over time.