Performance plastic resins for electronics advancing broadly
By Don Rosato

Share this article:  

Note: This is the second article of a four-part series covering electrical and electronic (E/E) device (1) trends, (2) material advances, (3) process technologies and (4) applications.


What is an important E/E device plastic resin trend?
  • 1. High heat
  • 2. High flow
  • 3. Chemical resistance
  • 4. Cost effectiveness

In commercial electrical/electronic (E/E) applications, polymer development is pushing plastic resin properties in response to ongoing demand for smaller electronic devices in which high heat and high flow grades permit more intricate, miniaturized parts in electronic applications. Let's take a look at new resin developments in these E/E target property areas.

Ticona has introduced a new generation of Thermx PCT (polycyclohexylene-dimethylene terephthalate) that delivers outstanding initial reflectance and reflectance stability required in electronic LED (light emitting diode) packages found in display backlight and general lighting. The PCT resin provides superior superwhite color and reflectance stability under heat and light compared to commonly in use high temperature polyamides (i.e., PA9T and PA6T).

Thermx PCT LED superwhite base package.

Thermx LED 0201 and Thermx LED 0201S are fiber-filled, superwhite PCT compounds. They withstand the demanding LED requirements for reflector resins with the following capabilities:
  • High initial reflectance
  • High reflectance stability under heat and light
  • Excellent silicone adhesion
  • Excellent processability
  • Excellent mechanical strength and flexibility versus high temperature polyamides
  • Surface mount technology reflow capability
  • Low moisture absorption
These polyester materials are lead-free solderable, with short-term heat resistance up to 260 degrees C and also have high Comparative Tracking Index (CTI) and arc resistance, high dielectric strength, and low dielectric constant. Chemical resistance to automotive fluids is also a bonus for automakers. Thermx LED 0201 is suitable for cost-effective LED lighting; while Thermx LED 0201S is suitable for more demanding applications such as flat-panel screens.

Next, the high demand for smaller, thinner electrical parts that must withstand hotter temperatures at higher electrical frequencies is driving development of higher melt-flow resins. DuPont recently introduced Teflon PFA 416HP, a new PFA (perfluoroalkoxy)-based resin for insulation of wire, cable and intricate electronic parts. This new fluoropolymer resin features a high melt-flow rate while maintaining very good MIT flex life.

MIT flex is a laboratory test where a film of plastic is continuously bent and flexed until it breaks. These characteristics offer coaxial wire manufacturers, semiconductor OEMs and electronic device designers the ability to coat ultrathin gauge wire and to injection-mold fine, intricate thin-wall parts in a more efficient manner than can be done with other fluoropolymers.

PFA 416HP melt-flow rate versus MIT flex life-to-failure cycles.

Teflon PFA 416HP provides all of the advantages of PTFE (Polytetrafluoroethylene) including ultrahigh thermal resistance and dielectric properties, combined with a very high melt-flow rate. The material also provides excellent chemical resistance, very good stress crack resistance and easy flow for molding applications.

PFA 416HP is particularly suitable for applications such as antennas for wireless electronic devices, cables for medical sensors and related components where high flowability of the melt and high stress cracking resistance are required.

Continuing, a new flexible polymer of high-performance silicone, Dow Corning WG-1017, has been developed to create optical waveguides on printed circuit boards that can withstand extreme operating heat and humidity with no measurable degradation in performance. The materials can be fabricated into waveguides using conventional manufacturing techniques available today. Board-level waveguides will help pave the way for the low-cost integration of photonics in energy-efficient supercomputers and data centers.

Scientists at IBM in conjunction with Dow Corning researchers for the first time fabricated thin sheets of optical waveguide. They show the following features:
  • No curling
  • Can bend to a 1 millimeter radius
  • Are stable at extreme operating conditions including 85 percent humidity and 85 degrees C

Silicone optical waveguide on printed circuitboard.

At left, prior formulation iterations on Kapton 300 MT polyimide showed severe curling (150 µm coating). At center, Waveguide builds (130 µm thickness) on Pyralux polyimide showing severe curling. At right, WG-1017 showed significantly reduced curling in a waveguide build (130 µm thickness) on Pyralux polyimide.

These waveguides have excellent adhesion to polyimide substrates and good performance sustained over 500 thermal cycles between minus-40 degrees and 120 degrees C. Optical waveguides from this silicone polymer technology offer new options for transmitting data substantially faster, with lower heat and energy consumption.

A key advantage of this new material is its reliability. Waveguides made with the material can deliver sustained good performance past 2,000 hours under high humidity and temperature. The robustness and flexibility of the new material make it and ideal replacement for traditional copper waveguides.

Conventional copper waveguides using electrical signals are prone to producing "crosstalk" or signal interferences that radiates from one copper link to the one adjacent to it. This slows down performance and eats up energy. This does not occur with silicone-based waveguides using light signals.

Another advantage of the material is its manufacturability. The silicone can survive the manufacturing process better than most materials, and its flexibility allows it to be easily shaped and made to fit various patterns.

Finally in our electronic materials review, improved PBT (polybutylene terephthalate) is taking on higher-cost engineering thermoplastics in electronics. PBT has a valuable combination of properties with the following key features:
  • exceptional resistance to heat, creep and chemicals
  • good processability
  • good economics for a variety of applications
The most important applications of PBT are for products used in the automotive, electrical, electronics, telecommunication and precision engineering sectors. With excellent electrical properties, PBT is often seen as having the best overall performance profile for E/E applications of all the engineering thermoplastics. Global demand for PBT in E/E applications accounts for nearly half of the entire global PBT demand.

In addition to compounding, additives such as flame retardants and antioxidants are used to improve material properties as well as to facilitate fabrication processes. PBT automotive end-uses include sockets, fuse boxes and junction systems. In the E/E market, PBT is used in connectors, capacitors, cable enclosures and similar components.

Global demand for PBT in E/E applications

Tokyo-based Polyplastics Co. Ltd. and its joint venture WinTech Polymer Ltd. have developed new Duranex PBT grades with improved low-temperature impact strength, hydrolysis resistance and high flowability. These are meant to compete with the more exotic and higher-cost PPS (polyphenylene sulfide) and LCP (liquid crystal polymer) resins.

The Duranex LT Series targets PPS substitution in applications in demanding environments like automobile sensors and electronic control units. These grades have improved low-temperature impact strength (20 times conventional PBT) while hydrolysis resistance has been improved by a factor of six. The Duranex SF series targets LCP applications — they possess flowability more than twice standard PBT, approaching that of LCP. This high flowability makes this series ideal for thin-wall electronic components.

Dr. Donald V. "Don" Rosato serves as president of PlastiSource, Inc. a prototype manufacturing, technology development and marketing advisory firm located in Concord, Mass., and is the author of the Vol 1 & 2 "Plastics Technology Handbook".