A workforce of researchers on the College of Washington (UW) has developed a printed circuit board (PCB) primarily based on a plastic materials, known as vitrimer, created lower than 20 years in the past.
Vitrimer PCB being laminated in a prototype dimension warmth press.
The vitrimer epoxy creates a PCB with electrical and mechanical properties much like commonplace FR-4 PCB materials. This materials allows an environmentally pleasant recycling course of that ends in near-complete materials restoration.
E-Waste: An Undesirable Byproduct of Trendy Electronics
Digital waste, or e-waste, is an efficient instance of the legislation of unintended penalties in motion. We design supplies for low price, sturdiness, and reliability—attributes that make recycling very troublesome. A PCB is a group of poisonous petroleum-based substances peppered with heavy metals with a semi-inert inner construction.
When an digital machine’s life is over, it could find yourself in a landfill the place toxins leach off over time, poisoning the atmosphere and losing the precious commodities contained therein. If it does find yourself being “recycled”, its destiny will not be what most of us would think about to be accountable recycling. It typically lands in economically depressed areas, the place subsistence laborers breathe in extremely harmful fumes as they burn the PCBs to get well small quantities of gold, silver, copper, and different metals.
Enter Vitrimer
PCBs are constructed with a construction consisting of a glass fiber mat impregnated with thermoset epoxy resin, known as a prepreg layer. Prepreg sheets are laminated with a skinny copper layer by which the digital circuit is etched. A number of layers are etched, drilled, and heat-laminated collectively to type a PCB stack. When the PCB layers are stacked, they’re put right into a high-pressure, high-temperature press, which finishes the curing course of.
The UW workforce used a materials known as vitrimer, a plastic first introduced in 2015. Vitrimer is a two-part thermoset epoxy that doesn’t require dramatically new or unique processing and guarantees a excessive diploma of recyclability with out dangerous unwanted side effects. As a polymer, epoxy is constructed of lengthy chains of hydrocarbons that intertwine in the course of the curing course of. For conventional polymers, curing is a method. As soon as the polymer chains are intertwined from full curing, they’re steady and can’t be non-destructively separated.
That is the place vitrimer supplies differ. Like polymers, vitrimer chains wrap and intertwine when cured, however they will additionally unwrap after they make contact with warmth or particular solvents. Vitrimer’s capability to unwrap permits its chains to be cured, uncured, and recured repeatedly with out degrading them, permitting for restoration throughout recycling.
Simpler Storage, Acquainted Course of
As a result of conventional PCB prepreg is barely partially cured, it requires cautious storage and has a restricted shelf life earlier than it should be discarded. Vitrimer prepreg sheets will be totally cured, permitting simpler and longer storage earlier than being put right into a completed vitrimer printed circuit board (vPCB).
Absolutely cured vitrimer prepreg will be bonded and recured with warmth and strain utilizing the identical press/ovens utilized in conventional PCB processing. So long as the board’s copper layers are intact, cracked or warped vPCBs will be despatched again right into a thermal press and totally repaired due to their uncure/recure capability.
Untangling the Bonds for Higher Recycling
When recycling time comes round, the vitrimer epoxy base will be fully dissolved and reused.
Working vitrimer-based PCB (left) and recycled and get well parts (proper).
First, the parts are eliminated by way of desoldering, and the copper is etched off. After that, the vPCB is handled with a solvent to separate the vitrimer right into a jelly type, leaving the glass fiber mat and steel PCB traces to be simply recovered. The UW course of has proven a 98% restoration and reuse of the vitrimer epoxy, a 100% restoration of the glass fiber and PCB metals, and a 91% restoration of the recycling solvent.
Will Vitrimer Work as a PCB?
In an effort to act as a viable alternative for traditional PCB supplies, vitrimer should have the same price and appropriate electrical properties. It should additionally survive meeting and rework and meet mechanical and security necessities.
Of their intensive testing, the UW workforce constructed a 2.4-GHz transmitter utilizing vPCB to simulate a typical IoT machine. The vPCB featured electrical and mechanical traits similar to FR-4, the most typical PCB materials in use. It additionally demonstrated sturdiness underneath manufacturing and rework much like FR-4.
All photographs used courtesy of the College of Washington.