#2018 / Monocoque Printed Circuits (Part 2)

The previous newsletter explored the basic concept of Monocoque Printed Circuits. I received many inquiries and questions about this new circuit technology. Circuit engineers and designers need a feasible 3D wiring method to use as an alternative technology in flexible circuits. A lot of money is budgeted for complicated wiring in the limited spaces of Smart phones, digital cameras and other mobile devises. Electronic circuits are formed in plastic framing or housing; an idea created by circuit engineers’ years ago and called Molded Interconnect Device (MID). Several processes were used to try and build 3D wiring on plastic parts, but these attempts were unsuccessful. The processes were too complicated and manufacturers could not justify using any of them due to the negligible amount of yields.
Columbus’ egg refers to an idea that seems simple after the fact (google it for the reference). A thick film circuits engineer was watching the vacuum forming process from a PET sheet, and wondered if the PET sheet could have a circuit on the surface. The thermal forming is a very common process to create transparent packages for general goods. Polymer thick film circuits are widely used to place electronic circuits on PET films.

The process is very simple as illustrated in the figure.  The thick film circuits are first screen-printed on thermo plastic sheets and formed in the die at the appropriate temperature.

Previously, MID manufacturers were not very successful in creating electronic circuits on 3D formed parts. Thanks to the film circuits engineer mentioned in the prior paragraph, various circuits can be created on flat plastic sheets that are then formed in a heated die set. Some mechanical stresses show on the corners of the formed parts, but several newly developed silver inks can minimize the distortions of the printed conductors. This simple process leaves us with reliable 3D circuits and a bountiful yield.
We are using a traditional assembling process. Traditional soldering is not available, but we developed an SMT process using conductive glue. Most of the connectors designed for rigid circuit boards and flex circuits are available with just a few minor modifications.
The technology is relatively new and does not have a long history in actual applications. The trials will make the Monocoque circuit technology universally accepted, especially for large volume consumer products once trials are underway. I am very optimistic with this technology

Dominique K. Numakura, dnumakura@dknresearch.com
DKN Research, www.dknresearch.com

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Headlines of the week
(Please contact haverhill@dknreseach.com for further information and news.)

  1. TPCA (PCB industry organization in Taiwan) 6/17
    May PCB shipment unexpectedly declined 4.6% from April. Rigid boards declined 1.3% and flex circuits declined 13.5% from April. But they keep positive growths from the same month of the previous year.
  2. Gifu University (Japan) 6/22
    Has co-developed a tiny antenna for tera Hz wireless telecommunication targeting beyond 5G and 6G. Size: 1.36 x 1.36 x 1.72 mm.
  3. Taiyo Yuden (Major component supplier in Japan) 7/1
    Has rolled out a new series of MCLL capable for 150 degree C assuming automobile use. Size: 1005 ~ 3225, Capacity: ~ 0.1 micro F.
  4. Rohm (Major device manufacturer in Japan) 6/17
    Has developed a new small size blue/green color LED with high reliability. Wave length: 505 nm, Size: 1.6 x 0.8 mm.
  5. Osaka Prefecture University (Japan)
    Has succeeded to develop a new cathode material for the all solid state secondary battery. The new material enlarges the battery capacity remarkably.
  6. SCREEN (Major equipment manufacturer in Japan) 6/29
    Has rolled out a new spin processor SP-2100 for 8” wafer or smaller. The company expects 8” or smaller wafers could be the major in IoT and 5G markets.
  7. Canon (Major electronics company in Japan) 6/30
    Has developed a new SPAD (Single Photon Avalanche Diode) image sensor with one million pixels for 3D cameras.
  8. Kyoto Semiconductor (Semiconductor manufacturer in Japan) 7/1
    Has developed a new InGaAs base photo diode capable for modulation of 40 GHz band considering over 400 Gbit/sec transmission. Size: 0.6 x 0.48 x 0.25 mm.
  9. Kioxia (Major semiconductor manufacturer in Japan) 7/1
    Has completed the M&A of SSD business from LITE ON in Taiwan. The company will continue to use current brand.

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