Hi my name is Freddie Hong, I am a PhD student at imperial college London
Today I am presenting our paper Thermoforemd Circuit Boards (aka TCB).
Fabrication of highly conductive freeform 3d printed circuit board with heat bending
This work has been co-authored and supervised by Dr Connor Myant and Dr David Boyle
TCB is a new personal fabrication technique for constructing free-form electronics with an arbitrary form factors that are challenging to construct using traditional digital fabrications tools.
TCB supports double sided circuit layout; providing the designers a higher degree of deisgn freedom for their circuit arrangements.
TCB is also copper electroplated and highly conductive and can support high power applications such as the hot wire-form cutters.
It can also be mechanically fixed to various objects and existing commercial electrical components.
In our research, we found that high fidelity techniques such as Molded Interconnect Devices (MID) and multi-axis silver ink-based machines; were out of reach for most individuals.
Due to the cost and complexities involved.
And for more user-in-the loop approaches the products were often limited in application due to their restriction to single-sided circuits.
in-addition to the extensive manual effort required in the manufacturing process.
We wanted to develop a method that had similar look and feel, performance of the MID devices and yet manufacturable with accessible desktop equipment
whilst also trying to establish an immediately employable technique. We found our motivation for developing TCB.
Developing this technique from the designer’s perspective, we wanted a method that was economical, commercially available, and convenient to construct while also being highly functional.
We therefore, decided to use a conductive PLA on an opensource FDM 3D printer which is owned by many individual hobbyists and designers already.
Also, it is Economical to use and easy to programmed.
Current problem with 3D printing interactive objects using conductive PLA is that the resistance of the printed trace is too high that it is only useful for lighting LEDs or constructing capacitive sensors.
Furthermore, due to the inherent characteristics of the layer-by-layer construction of additive manufacturing, the resistance of the printed trace differ for every angle.
The resistance of the printed trace for vertical direction is at least 7times higher than the trace for horizontal directions.
This severely limit the design freedom of 3D printed electronic beyond XY plane.
As shown in the two samples, the layer structure between the points A, B and C differ significantly for the planar construction in comparison to the thermoformed sample.
This motivated us to develop a method of thermoforming flat 3D printed trace into 3D object,
which can maintain the same layer structure for inclining angles and hence provide more consistent resistance across the all areas of the surface.
The two illustration here shows the differences in the layer structure between the thermoformed traces and traditionally constructed traces.
We first tested the feasibility of thermoforming the conductive trace on LED circuit
We first printed the flat, double sided circuit board on our opensource 3D printer, then Heat bent it to the shape as shown on the right image
After shaping it to the desired form, we then copper electroplated the board using a commercially available copper electroplating kit.
Then, we adhered the electrical component using conductive silver ink and super glue.
We were able to 3D print the trace as thin as 0.5mm, thermoformed it and copper electroplate.
We used hot air-blower to heat up the PLA and bend it to the shape
As seen in this video, due to the low glass-transition temperature of the PLA (which is below <60c) the PLA become compliant to thermoforming very quickly.
This is a straight-forward and convenient process where the user can utilize their intuition and make alterations to the shape in a real-time feedback.
To design TCB, we developed a parametric design editor within a common Computer Aided Design software called Rhino and grasshopper.
In this design editor the user can use the points on the surface to draw the interconnect, locate VIAs, sockets and electrical components.
At any point during the design process, user can adjust the width and height of the conductive trace by adjusting the values on the slider.
At the end user can bake the geometry and export it to 3D printing slicer.
Using this technique, we were able to fabricate various free-form circuit boards that are double sided and highly conductive.
You can find more information about our work and the literature in the paper now archived in ACM’s digital library.
Thank you