Design007 Magazine


Issue link:

Contents of this Issue


Page 109 of 127

110 DESIGN007 MAGAZINE I SEPTEMBER 2019 sheet with the silver circuit is formed to de- sired 3D shape (Figure 2). Lastly, the formed circuit is removed from the die and cooled down. Then, a 3D-printed circuit is ready for the assembling process. Unfortunately, this soldering process is not available for thermally formed circuits. In- stead, a low-temperature SMT process with conductive glue was introduced for the mount- ing of the components. Conductive ink could be the key to this tech- nology. As the conductors have serious ten- sile stress during the thermal formation, the conductor materials have to have appropriate elasticity to avoid cracking. Certainly, standard copper foils cannot withstand the mechanical stress during thermal forming. Silver inks pre- pared for the thick film could be practical can- didates as the conductor of the circuits. However, the physical properties are not enough as the conductor of the formed cir- cuits; therefore, a new version of the conduc- tive ink has been developed. The new silver ink has higher elas- ticity and can with- stand mechanical stress during ther- mal formation. But conductor patterns have several limita- tions, especially in the bent area. De- sign guides, such as the minimum ra- dius of the corners, should be provided by manufacturers. As it is still in the development stage, there are not many examples. Right now, most manu- facturers are us- ing PET as the sub- strate material. The trials are showing very promising per- formances. Manu- facturers have been expanding the substrate materials to acryl- ic resins and polycarbonate resins, which are popular as packaging materials for food. More materials will be tried out in the next few quarters. Formed printed circuits are not categorized as rigid printed circuits nor flexible circuits. We are calling them monocoque printed circuits because the formed structure works as both the framing of the packages and the substrate of the circuits. This new circuit technology needs a new category. Originally, "monocoque" was a French word used in the design of automo - biles. Monocoque structure means a specific construction in which the body also works for framing to support the weight. FLEX007 Dominique K. Numakura is the managing director of DKN Research LLC. To read past columns or contact Numakura, click here. Figure 2: After thermal forming.

Articles in this issue

Links on this page

Archives of this issue

view archives of Design007 Magazine - Design007-Sept2019