Although each of the banned chemicals offered advantages for PCB manufacturing, the industry has found alternatives that provide the same (or even better) performance and reliability. Rather than use lead-tin solder, for example, PCB manufacturing processes rely on tin-silver-copper solder. Even though silver is a hazardous material, the small amount used in tin-silver-copper solder does not have a harmful environmental impact.
Along with tin-silver-solder, PCB manufacturers also use silicone and polyamide polymer adhesives that include small embedded flakes of silver to achieve high conductivity and tight bonding to circuit boards. Other lead-free solder technologies include electroplating, solder ball formation technologies, and solder dipping technologies.
The switch to lead-free soldering also prompted design teams and manufacturers to collaborate to achieve simplified layouts with tightly packed components. As a result, manufacturers gained the ability to fabricate smaller boards at lower costs.
Paper PCBs Provide Another Alternative Solution
Aside from the RoHS-banned chemicals, PCB manufacturers have begun moving away from the use of glycol ethers, formaldehyde, and dimethylformamide in production processes.
Paper PCBs (P-PCBs) that mount components on flexible paper substrates combine reliable functionality with environmentally-friendly, renewable materials. P-PCBs rely on lead-free, electrically conductive adhesives that connect surface mounted components to tin or zinc conductors. These conductors transfer to the paper PCB through screen printing, 3-D printing, or inkjet printing.
Prototype papers PCBs have demonstrated the same functionality as traditional circuit boards in terms of electrical conductivity, reliability, multilayer capabilities, and resistance loss. A typical P-PCB fabrication process involves using additive technologies to print the ECA onto each layer of paper substrate. The next step includes curing the adhesive, aligning the layer-by-layer circuits, and then adhering the layers to one another with pressure-sensitive adhesives. After the punching of vias through each layer, the process continues with mounting surface-mount devices to the conductors.
While paper PCBs remain in the prototype stage, developments in advanced paper materials promise to deliver properties that allow the use of paper-based technologies for high-speed, high-density applications. The advancements in paper materials offset the loss of properties seen with RoHS-banned materials through improved electrical and thermal conductivity, enhanced fire resistance, moisture resistance, and improved dielectric properties.
While the industry has come far in terms of how PCBs are manufactured, we still have a long way to go towards creating an environmentally-friendly manufacturing process. For tools to assist you with your next sustainable design, visit Cadence’s PCB Design and Analysis Software page. The Allegro PCB Editor helps you create accurate, quality designs. You can also use AR to accurately assess and improve PCBs using augmented reality and intuitive interaction. Inspecting, debugging, reworking, and assembling PCBs has never been faster or easier.
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