Plating on SLA Plastic
Stereolithography (SLA) plastic is created directly from 3D CAD data without tooling. Liquid plastic (photopolymer) is converted into solid cross-sections with the use of an ultraviolet laser, and the part is created layer by layer. Each resin layer is built on the next until the entire SLA plastic part is completed. SLA materials range widely in their mechanical properties and possible applications. Common SLA materials include standard resin, engineering resin, castable resin and more. Plating on SLA plastic provides additional attributes needed for many industrial projects.
Benefits of Plating on SLA Plastics
Additive manufactured parts for industrial applications can undergo electroless plating and electroplating. Completing these processes gives SLA polymer components a number of advantageous qualities for increased functionality, aesthetics, sealing and more. Among the many benefits are:
- Higher heat deflection: Electroplating gives SLA plastics a higher capability to withstand hot conditions, which is important in many applications that require high strength and heat deflection.
- Increased strength: With different electroplating options, including copper and nickel, tensile strength has been shown to increase in SLA plastic by 10 to 12 times. Flexural strength increased by 21 to 24 times in comparison to parts without electroplating..
- Better chemical resistance: The metal electroplated onto a component provides a barrier that protects against chemicals that could otherwise damage or corrode the part’s material or change its properties.
- Enhanced aesthetic value: While functional enhancement is more relevant to industrial applications for SLA plastic, electroplating does give parts a shiny appearance without users needing to pay for the production of a completely metal part.
Electroless Plating on SLA Plastic
In order for electroplating of SLA plastic to take place, electroless plating must first occur to metalize the non-metallic plastic substrate and give it adhesive properties. This happens through electroless plating, a process that involves depositing metal onto the substrate surface without an electric current in the plating bath. Many people choose electroless plating by itself, while others decide to add electroplating for increased thickness and durability.
Before either plating process occurs, the plastic part must be molded so it is ready for plating without stress or surface imperfections that usually lower the component’s quality. Once ready, the molded part should meet specified parameters for melt temperature, polishing and drying of the resin. When the substrate is prepared, a series of steps take place for electroless plating. The steps can vary depending on different elements of the project, but they should include most of the following:
- Cleaning: The substrate surface could have dirt, dust and fingerprints before plating. It must be carefully cleaned before the plating process can continue. An alkaline solution usually suffices to get the job done, but sometimes wetting is necessary, which can be achieved with a chromic acid solution.
- Pre-dipping: Pre-dipping involves placing the plastic components into a solvent before etching, which improves the exterior of parts that have been poorly molded or are highly stressed. The process also swells the surface of hard-to-etch components, which enables the etchant to access the entire surface.
- Etching: Usually consisting of sulfuric acid or chromium trioxide solutions, etchants increase a substrate’s surface, which makes liquid absorption by the component easier. In addition, etching creates microscopic holes that allow bonding with any deposited metal.
- Conditioning: Conditioning is not needed, but adds benefits. Conditioner is applied to the substrate to promote uniformity in absorption during the later activation stage.
- Neutralizing: Before neutralizing, the part needs to be rinsed to eliminate excess acid or other possible foreign materials. Neutralizing takes place after etching and rinsing to help ensure any extra etchant is entirely removed. A common neutralizing product designed to properly remove excess etchants is sodium bisulfate.
- Pre-activating: Also optional, a pre-activator is designed to enable absorption in the next step. If a conditioner has already been used, plating professionals must apply pre-activators with caution to avoid excessive substrate conditioning.
- Activating: During activation, a liquid activator with a low concentration of precious metal is introduced that will serve as a catalyst during the plating process. It also greatly lowers drag-out fees. Common metals used in these activators include gold, palladium and platinum.
- Accelerating: An accelerator will remove extra stannous hydroxide from any component. This allows the activator more effective fulfillment of its catalyst role. Accelerators also work to prevent skip-plating occurrences.
- Bath immersion: After the plastic parts are rinsed, they’re placed in an electroless bath, which is where a thin metal coating is deposited. Nickel is the most common choice for a wide range of applications, but copper plating is also performed on some plastic substrates. Nickel provides adequate conductivity, but copper is chosen at times for automotive components, since it has less blistering resistance.
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Types of Electroless Plating on SLA Plastic
Two different classifications apply to electroless plating. The first and more affordable option is all-over plating. The metal is coated over the whole surface of the SLA plastic substrate. Thickness ranges from 40 to 2,000 micro-inches. It’s more cost-effective because it almost always takes far less time and precision.
The other electroless plating option is selective plating, which involves depositing metal onto precise surfaces on the plastic component instead of depositing it over the entire part. Items in this process are not exposed to aggressive chemicals that could cause undesirable changes to texture or color. Thickness achieved by selective plating ranges from 40 to 400 micro-inches. The higher precision required to keep plating on select sections makes it a more expensive process to complete.
Electroplating on SLA Plastic
Electroplating adds additional thickness to SLA plastic, which is required for certain applications. Rate of deposition can be increased by up to 10 times when an electric current is added into the plating bath. The higher thickness from electroplating adds benefits over electroless plating alone: higher corrosion resistance, greater protection against abrasions and increased durability, to name a few. These advantages make electroplating the most common and popular choice for heavy-duty industrial applications.
The process involved with electroplating starts with an electrolytic solution, referred to as a bath. We connect the plating metal, or coating, to an anode (electrode with a positive charge) of an electrical circuit. Next, the SLA-plastic substrate is placed at a cathode (electrode with a negative charge). We immerse both in the bath and supply a DC current to the anode. The atoms of the metal are oxidized and dissolved into the bath. The dissolved metal ions get reduced at the cathode and then plated onto the plastic.
Electroplating costs more than the process of electroless plating and makes it harder to reach a uniform thickness over the entire substrate, because the thickness often builds faster on the surface edges. Plastic substrates that have deep recesses in their surface are not ideal candidates for electroplating, because the plating solution often quickly becomes trapped. Therefore, electroless plating alone is a more effective option for some SLA plastic substrates.
Most Common Metals and Alloys Plated Onto SLA Plastic
At SPC, we offer a number of metals and alloys to plate SLA plastic through either electroless plating or a combination of electroless plating with electroplating. Nickel, copper and gold are all options.
Nickel has a bright, metallic appearance and provides resistance against corrosion and wear on the piece. Nickel alloys typically include metals like tin, tungsten and others that increase the hardness of the nickel deposit and further improve resistance against wear and corrosion.
Copper is recognized for its high electrical conductivity. Copper plating is an extremely popular choice for metallizing non-conductive surfaces. It’s also frequently chosen because it can be used as a heat stop-off for masking and has a low cost in comparison to gold, silver and other precious metals.
Gold, like silver, obviously improves the appearance of plated components, but it also offers important functional benefits like electrical conductivity, heat shielding, corrosion resistance and more. A gold-plated SLA plastic part will have more functionality in high-temperature applications from the temperature resistance gold plating offers.
Benefits of Choosing SPC for Plating on Your SLA Plastic Parts
Plating on SLA plastic parts isn’t performed by many other plating companies because of process complexity. Even fewer companies will work with 3D-printed plastic parts. When you choose to partner with SPC for electroless plating and electroplating on your SLA plastic, you’ll have access to those services and several benefits you won’t always get with our competition. We work to differentiate SPC from other companies in the industry, which gives our customers unique advantages.
At SPC, we’re focused on innovation and have been since our inception in 1925. We constantly improve our surface treatment work, from preparation to the final plating on SLA plastic parts and other components. We continue to be a family-owned company with only the best employees, most educated chemical engineers and other accredited industry professionals. Our team goal is total customer satisfaction and we strive for social responsibility along the way too, including community improvement and eco-friendliness.
If you’re ready to start discussing plating on your SLA plastic parts, look no further than SPC. We’ll help you determine which options are best for your budget by offering a free quote within a single business day of the time you contact us. Our friendly and knowledgeable professionals will help you decide what the best metal and process are for your SLA plastic. We’ll answer your questions and provide the range of products and services you need. Reach out now to get started.
LEARN WHAT OUR MANY SATISFIED CUSTOMERS HAVE TO SAY ABOUT Us
"I would like to thank you for the help you have provided us in developing an electroless nickel plating technique on an unusual substrate. The sample platings you provided show that we should be able to reach our goals. I especially appreciate your willingness to take on an unusual job, with the uncertainties that that entails...We are looking forward to working with you in the future on our plating needs."
– Robert K.