Polyimide

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Flexible RFID tag loop printed onto Kapton sheet
555 Timer based circuit printed onto Kapton (backed with balsa for rigidity in this case)

Click here to see a full list of substrates that can be used with the Argentum printer.

Description

Please note that the following refers to Polyimide as the pre-processed substrate produced by Cartesian Co. The current revision of Polyimide is a sand blasting surface treated sheet measuring roughly 150x100mm.

Polyimide sheeting (often known as Kapton) is a thin, flexible, high temperature plastic that is considered the industry standard for flexible electronics. It's most useful as a substrate that can be cut into shapes very easily while being very flexible. Polyimide can also be soldered to quite easily & does not stain from the Nitric Acid chemical byproduct of the ink reaction. Unfortunately, the smooth surface of stock Polyimide sheeting does not provide a surface conducive to bonding the Silver traces & it must be pre-processed before printing onto.

Where to find

Pre-processed sheets of sanded Polyimide will be able to be purchased from the Cartesian Co Web Store shortly. Sheets of Kapton/Polyimide can also be found from various suppliers online (in particular, wide Kapton tape has become popularized by 3D printing) but note that in order to achieve high resolution & conductivity, the surface must be sanded to a very even & fine finish.

Coming soon: details of pre-processing steps to take stock Kapton to a state ideal for printing with the Argentum.

Parameter Details

Property Value Description
Conductivity.jpg
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5/5 The conductivity of Polyimide is extremely favourable due to the fact that it has been sand blasted to an ideal roughness before shipping. This means the surface doesn't have any matrix weaving that the Silver tracks fall into (eg. Linen Paper) & a continuous conducting path is built up & filled in very quickly.
Resolution.jpg
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5/5 For very similar reasons as the conductivity being beneficial, the resolution achieved on a Polyimide sheet can be very high. The resolution on Polyimide seems to be limited only by the cartridge resolution and the viscosity of the ink. It is easy to print footprints for 0603 components & if you tune your printer correctly & keep your cartridges in good condition, it is possible to create footprints as fine as TSSOP (0.635mm or 0.025inch pitch spacing).
Solderability.jpg
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3/5 Polyimide achieves its high conductivity and resolution at the cost of ideal bonding to the Silver traces. With some practice, Polyimide can be soldered to very easily but at first try, it is possible to pull up the Silver traces as the solder re-flows by using too high of a temperature. Polyimide is however ideal for use on a re-flow hot plate, heat gun re-flow soldering as well as hand soldering.
Durability.jpg
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4/5 Polyimide as the substrate is very resistant to tearing, entirely waterproof, non-combustible & will not warp under heat. As mentioned above, in some cases the adhesion of the traces onto the substrate will not be particularly strong - this means that it is possible to scratch the trace from the material.
Flexibility.jpg
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5/5 Polyimide is a very flexible, thin plastic substrate, it can be bent & folded repeatedly without any damage to the substrate - it will also resist tight folding which reduces the risk of breaking the Silver traces. For these reasons, Polyimide is the industry standard material for flexible circuit boards.
Formability.jpg
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5/5 Polyimide cannot be folded or torn but is very easily cut with scissors or a knife, it can also be laser cut without producing toxic fumes. Polyimide is ideal for creating uniquely shaped PCBs.

Compatible Component Attachment Methods

Soldering
Solderability.jpg
Silver Conductive Epoxy
ConductiveEpoxy.jpg
Z-Axis Tape
ZAxisTape.jpg