2022

What is Tin Electroplating?

Tin electroplating is the process of using an electrical current to create a chemical reaction to produce a layer of tin plating onto a ferrous or nonferrous substrate. The electrical current travels through an aqueous solution of tin chemistry and a positively charged tin anode, causing the tin in the solution to attract onto the metal parts attached to a negatively charged cathode. The result is a soft, silver-white deposit of tin on the desired substrate.

What Are the Different Tin Plating Processes?

The type of method used for tin plating relies heavily on the configuration of the part and on customer requirements. No plating method is inherently better than another, but one will be more appropriate over another based on the limitations of a part.

• Barrel Plating – Barrel plating is typically reserved for small parts that can withstand being slowly tumbled in a rotating barrel that is dipped into the plating solution. Due to the nature of how the parts make electrical contact with the cathode, this method can take longer to achieve uniform coverage. Parts that are very thin or made of a soft substrate should not be barrel plated.

• Rack Plating – Rack plating is ideal for larger parts or parts that are thin and flat that would otherwise be damaged in the barrel method. Rack plating mitigates the chance of damage, shadowing or adhesion issues that can otherwise occur from thin and flat parts sticking to one another. Metal wire is either wrapped around the part or threaded through a hole or slot of the part then hung from special racks that allow the negative charge to pass through and make electrical contact with the part to plate.
• Vibratory Barrel – A vibratory barrel is a specially designed basket with a vertical shaft in the center. A generator emits a pulse through the shaft causing the parts to gently vibrate around the axis. While gently vibrating around the axis, the parts maintain electrical contact with the cathodes at the bottom of the basket creating a uniform deposit. This method is usually reserved for thin, fragile parts with fine points or contact pins.

Types of Tin Electroplating

Matte Tin Plating – Matte tin has a dull surface appearance because it does not contain any brightening additives. The lack of brighteners allows matte tin to maintain excellent solderability and ductility.

Bright Tin Plating – Bright tin contains additives that tighten the grain structure of the deposited metal, creating a shinier, more cosmetic appearance. Due to the tightened grain structure, bright tin is also more resistant to discoloration over matte tin. However, there is a risk of the bright tin burning when soldered due to the addition of the brighteners.

Tin Lead Plating – Lead alloy is added to pure tin to combat the phenomenon of “whiskers” occurring in the pure tin. The common co-deposit of these two alloys are 60/40 tin lead and 90/10 tin lead. The added lead alloy lowers the tin’s melting point from 450ºF to 361ºF. This lowered melting point makes tin lead an optimal choice in electrical applications for its superior solderability.

Bismuth Tin Plating – Bismuth tin is an increasingly common RoHS-compliant alternative to tin lead with a co-deposit of tin and bismuth. Bismuth tin is capable of withstanding long-term cold exposure, combating the condition known as tin pest. The added bismuth deposit also makes the tin whisker resistant.

The Benefits of Tin Electroplating

• Excellent Solderability – Compared to other heavy metals, tin has a very low melting point of 232ºC/450ºF and even lower melting point of 182ºC/361ºF when co-deposited with lead. This makes tin an ideal candidate for soldering applications and increasing the overall solderability of the substrate.
• Ductile – Tin is a soft metal that is very flexible. Manufacturing companies can easily form, stretch, and mold the plated substrate into different shapes without cracking or harming the adhesion of the plating.
• Cost-Effective – Tin electroplating is cost-effective and easy to obtain compared to other electroplated metals like silver with similar soldering properties and can be plated onto almost any metal.
• Corrosion Resistant – Tin has good corrosion resistance in protecting the substrate.
• Non-Toxic – Tin is widely considered non-toxic and often used in the form of tin cans covered in lacquer. The ductility of the tin allows the tin to be formed, stamped, and shaped without damaging the tin adhesion.

Tin Electroplating Considerations

Whiskers – Whiskering is a phenomenon that causes metal filaments to occur on the surface of pure tin plating. Whiskers can appear soon after plating or take years to appear. These crystalline structures can be .0001 inch in diameter and can stretch 3/8 inch or longer, with the capacity to carry current. In the majority of applications, the growth of whiskers is not an issue. However, pure tin is not recommended for applications with low-voltage electrical equipment where items are closely spaced. As the whiskers can cause electrical shorts or current arcs and critical disruptions in the electronics. Underplates like nickel can help reduce the risk of whiskers or co-depositing the tin with a minimum of 2% lead or bismuth.

Low Melting Point – While the low melting point of tin is ideal for soldering applications, the limited temperature window of tin restricts the number of appropriate applications outside of soldering. Tin on steel faces difficulty due to the high temperature typically needed to relieve the steel of the embrittlement.

Tin Pest – Also known as tin disease. Occurs when the structure of the pure tin molecules expands and moves away from its cubic structure. The molecular change becomes greatly unstable in the presence of low temperatures. Due to the unstable nature of the structure, the tin can lose adhesion to the substrate and loses conductivity. Ultimately, the tin becomes incredibly brittle and disintegrates at an increasing pace. Tin pest is at great risk of forming in temperatures in -22ºF to -40ºF, but still poses a risk at prolonged temperatures of 56ºF and cooler. Tins co-deposited with lead or bismuth do not experience the same risks.

Tin Oxide – Care should be taken while handling and storing tin-plated items. Tin oxide naturally occurs in a clean, dry atmosphere with continuous airflow, but the oxidation rate is very slow. If the tin is stored in a warm, humid environment with little airflow, the oxidation occurs at a much more rapid rate. A thick dull gray oxidation layer will form requiring the oxide to be broken through before successful soldering can occur. Using a resistance paper during packing or storage of a tin-plated part will help slow down the oxidation and mitigate tarnishing.

Staining – The structure of the tin makes it susceptible to staining and discoloration as it absorbs moisture and oils verify easily and is not easily cleaned without burnishing the finish. Gloves are recommended in handling tin-plated parts to avoid staining or discoloration.

Fretting – When used as a contact, micro-motions and repeated mating and disconnecting of the contacts can cause fretting corrosion and wear away the tin coating. The amount of fretting can depend on the thickness of the tin deposit on the contact and can be countered with lubrication. Note: gold and tin should never be mated as a connection.

TIN ELECTROPLATING PROCESSES FOR AEROSPACE AND DEFENSE

Multiple industries utilize tin electroplating for its desirable properties — like low cost, high ductility, and high solderability. INCERTEC specializes in tin electroplating complex parts for the aerospace and defense industries and testing them in accordance with strict NADCAP requirements.

Most of the parts tin lead and bismuth tin plated at INCERTEC are electrical components, standoffs, and electrical housing. These electrical components are later assembled into circuit boards with standoffs and housing that allow for the continued air circulation.

INCERTEC PLATING LINE SERVICES

Tin electroplating is only one of the plating services offered at INCERTEC. The goal at INCERTEC is to always have the space and capacity open to partner with customers to scale production through dedicated plating lines.

PLATING THE UN-PLATEABLE PLASTIC PBT CONNECTORS

How determination and innovation laid the foundation of metal finishing on uncommon substrates at INCERTEC

Deutsch Automotive Group, a California-based connector company, was creating connectors for the power module in Renault’s new electric automobile the Fluence Z.E. This connector was made of PBT (Polybutylene Terephthalate) a thermoplastic polymer often used by engineers and manufacturers for its high strength, heat resistance, electrical insulation, and chemical resistance properties. Thus, creating a durable cost-effective product without compromising performance.

All that remained was for Deutsch to make the PBT connector electrically conductive by adding a layer of metal. Even though a few companies in Europe had meager success in plating PBT, it was (and still is) widely acknowledged as “non-plateable” by US metal finishing companies who routinely plated composite materials.

PLATING ON PLASTIC

A plating shop in Fridley, MN was eager to take on this challenge. Established in 1993 as Spec plating and newly renamed INCERTEC to reflect the company’s dedication to innovation, certifications, and technical abilities, INCERTEC was determined to prove out its new name.

Product development manager Jerrid Matson and INCERTEC’s onsite chemists got to work testing different forms and combinations of pre-treatment on the PBT substrate. Solidifying this process was imperative to the success of the entire project. Creating an initial bond by increasing pore sites in the base material enables it to receive the proprietary chemistry and become seeded, creating the metallization layer. Once a part has been metalized, it is no different than any other non-ferrous or ferrous metal and could be plated with typical electrolytic or electroless plating processes.

SELECTIVE PLATING

Adhesion of the metal plating to PBT connectors was not the sole obstacle INCERTEC had to contend with. The team had to selectively plate and define demarcation lines where the substrate was to remain untouched by the metallization process. Custom rubber masking molds were procured with the intent to mask off specific areas efficiently and effectively, but the masking molds could not create a strong enough seal to prevent the plating from leaking into the undesired areas.  INCERTEC had to reallocate internal resources to hand mask the plated PBT connector resulting in a heavily involved multi-step process cycling with pretreatment and post finishing.

SOLUTIONS BASED RESEARCH & DEVELOPMENT

Weeks went by as the research and development team frequently put in 14-hour days testing and fine-tuning processes and determining the best method for the selective plating. Days were long, but spirits were high as the team continually moved closer to success, driven by the internal motivation to prove to Deutsch and themselves that INCERTEC had the quality and the expertise with plating on plastic to tackle a seemingly impossible feat. Within 3 months of taking on this Goliath of a project, INCERTEC was successfully plating the un-plateable PBT.

A PROCESS PROVEN

By early May 2011 INCERTEC proved out the process with continued success and received its first skid of Deutsch connectors. This was the first full-volume project INCERTEC had seen. Everyone came together as a team to accomplish the unprecedented high volume, repetitive work. The workflow was then simplified to a dedicated plating line style process. Creating easy-to-understand work instructions and training with the ability to pull in more resources, while still creating repeatability.

By late 2011, INCERTEC transitioned the Deutsch plating operations to its new state-of-the-art metal plating facility in Empalme Sonora Mexico and continued plating PBT connectors until Deutsch was bought out by TE in April 2012.

We took something that said it couldn’t be done in the US, and inside of 3 months it was being run by people who had no idea how difficult what they were doing actually was.

-Jerrid Matson looking back on the successful endeavor.

THE TECHNICAL ABILITY OF INCERTEC

Since the plating of the first Deutsch connectors, INCERTEC has continued to increase its capability of plating on unique substrates like composites, magnets, and ceramics. If you have any questions about how we can help you solve a plating challenge, contact us today to learn more!

While this inspection method is relatively simple, fluorescent dye penetrant testing expedites the testing of non-porous materials. we can effectively identify any flaws in your part without using harsh chemicals or substances that may damage its functionality.

In addition to its non-destructive qualities, fluorescent dye penetrant testing provides:

• Faster identification of flaws in the material: This process makes the flaw indication much larger than the flaw itself. This makes it possible to identify flaws that are not visible by the naked eye, such as those smaller than 0.08 mm.
• High reliability for flaw detection: There is a high level of contrast between the flaw indication and the background material with this process.
• A testing solution for a wide range of materials: It’s possible to use this method for   metallic, non-metallic, magnetic, and electrical insulator materials.
• An effective way to test large amounts of material: The simplicity of fluorescent dye penetrant testing means that it streamlines the inspection process.

ADDITIONAL ADVANTAGES OF FLUORESCENT DYE PENETRANT TESTING

Identifying flaws in a part eliminates the possibility of having to scrap it further down the line in production. We take a proactive approach to inspection to enhance the predictability of your operations. When you can be sure that your part is not hiding any flaws, you can be certain that it will work the way you expect.

Testing to these standards requires experience and a familiarity with the industries that demand near perfection in their parts. INCERTEC assures quality for those in aerospace, medical and other industries that need a surefire plating solution.

FLUORESCENT DYE PENETRANT TESTING SERVICES

At INCERTEC, we provide services with the utmost transparency for our customers. If you have any questions about our ASTM E1417 fluorescent dye penetrant service testing standards or how we can help you solve a plating challenge, contact us today to learn more!

Dedicated Plating Line Services

The Ultimate Partnership

Metal finishing is a service industry charged with turning customer parts quickly and accurately. But what happens when a metal finisher hits capacity constraints? Or worse, encounters quality issues that snag a whole project?

What is the plating line process?

Line plating is the practice of depositing metal alloys onto a metallic surface through a process of chemical baths. Most plating baths have an electrical current to coat the metal. Other plating baths have no electrical current, known as an autocatalytic chemical process. The parts move from bath to bath through means of automated machinery or by hand by a plater. Once the parts have gone through the plating line process, a new layer of metal coats the part. This new layer of metal preserves the substrate, increasing the corrosion resistance. Electrical conductivity may also change depending on the chosen deposited metal.

Most finishing shops attempt to capture a diverse customer base by catering to many industries, building an inventory of standardized tooling and one-size-fits-most technology. This mentality is not suited for high volume, repeatable work. Creating repeatable, high-quality results, requires the equipment to remain dialed in to precise specifications. This can be accomplished with a dedicated plating line process.

What is a dedicated plating line?

A dedicated plating line uses the plating line process but is designed, planned, and equipped to only run a customer’s specific part or part family within a plating shop. Simply put, finishing tanks and equipment are designed for a single customer at their disposal, including dedicated labor.

The customer controls what, when, and how much goes through the line. When parts are outsourced for plating, the metal finisher dictates the price and lead time based on information from the purchase order and print. The lead time can also vary depending on the finisher’s backlog and available labor.

A dedicated line can be designed around meeting price targets, lead times, quality requirements, line contamination and FOD.

When considering a dedicated plating line, it is important for the customer to reflect on what organizational goal and competitive advantage is being accomplished through the dedicated line. What is important to the organization?

When are dedicated plating lines appropriate?

Dedicated plating lines are scale driven. Most plating companies cannot handle a large daily increase in capacity and still effectively serve its customer base. A dedicated plating line comes with all the benefits of vertically integrating, minus the day-to-day headaches.

Many manufacturers prefer to focus on their core competencies with no desire to vertically integrate the metal finishing operations. Others lament the amount of overhead frequently wasted on additional quality and purchasing efforts from outsourcing metal finishing to multiple vendors while attempting to meet their customer’s lead times. A dedicated line solves both.

Disadvantages of Vertically Integrating Metal Finishing

Vertically integrating metal finishing has a high barrier to entry. Waste treatment and disposal, EPA regulations, skilled labor, special certifications (NADCAP, ITAR, AS9100, ISO 9001) are all expenses and responsibilities that cannot be ignored.

Vertically integrating involves a certain level of risk. For example, plating facilities are notorious for starting on fire. It is one thing to bring down a plating operation, but it is detrimental if it brings down the rest of the manufacturing process.

Questions to Ask Before Creating a Dedicated Line

There are a few circumstances to consider when talking about dedicated plating lines.

• What is the longevity of the project?
• Is this existing work that has been running for years and will likely continue for years to come?
• Is this work a new part or part family that could run for several years?
• Does it make sense to the bottom line?

Dedicated plating line services come with a price tag and need to generate a certain level of sales per square foot while meeting customer price targets to make sense. The ROI should benefit everyone involved.

INCERTEC PLATING LINE SERVICES

The goal at INCERTEC is to always have the space and capacity open for dedicated plating lines.  INCERTEC has grown significantly based on this principle of partnership. Partner with us and we will work with you to find the best solution.