Solderable Gold Plating of Electrical Contacts

Gold has and continues to be a principle finish for electrical components especially with the continuing miniaturization of electronics.  One of the primary benefits of gold plating services is a finish that is both conductive and receptive to soldering. When soldering gold plated components there are a variety of important considerations when specified the surface finish. The primary considerations are thickness, purity and the proper selection of an underplate.

Plating Thickness

Gold plating thickness is a critical, and often misunderstood, tenant of gold soldering. In gold soldering the physical bond is made between the underlying nickel layer and the solder itself, with the gold layer serving as barrier to help maintain the solderability of the nickel layer. Typical gold thickness for solderability is in the range of 10uin to 30uin as it provides adequate protection against oxidation to preserve wetting while keeping the cost of the finish as competitive as possible.

 

When soldering, gold dissolves into the solder through solid state diffusion.  With heavier gold deposits, more gold alloys within the solder joint.  In the diffusion process the gold reacts with the solder creating a gold intermetallic amalgam.  If the gold in the solder exceeds 3% by mass, the solder joint can become embrittled causing joint failure, especially in dynamically or thermally stressed joints.  The level of impurity and thickness of gold are directly related, thus thickness of the gold must be balanced between corrosion/oxidation protection, contact cycle life and solderability.  (Soldering to Gold – A practical Guide).

 

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Gold Plating Thickness of Connectors

Gold Plating Thickness of Connectors and Contactsgold plating services pins

Proper specification of gold plating thickness for connector and contact applications is a key design consideration.  Gold plating is an exceptional finish for connectors of that demand both high reliability and durability; however, the thickness of the gold plating will impact the durability and ultimate cycle life of the connector.  Gold plated connectors have low contact resistance which is suitable for applications with low signal voltages and current in the millivolt and milliamp range.  Because gold is a noble metal, it does not readily react with chemicals in most environments, meaning that gold plated connectors will retain their conductivity over time provide the thickness of the gold provides a sufficient barrier to the substrate from the environment.

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Hard Gold Plating vs Soft Gold Plating – Which is Right for My Application? 

Hard Gold Plating vs Soft Gold Plating – Which is Right for My Application?

 

When specifying gold plating services for an application, the question of hard gold plating versus soft gold plating is common design topic.  Hard gold plating is a gold electrodeposit that has been alloyed with another element to alter the grain structure of the gold to achieve a harder deposit with a more refined grain structure.  The most common alloying elements used in hard gold plating are cobalt, nickel or iron.  Soft gold plating is the highest purity gold electrodeposit that essentially is pure gold without the addition of any alloying elements.  Soft gold plating produces a more coarse grain structure that is free of any signficant codeposits.

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Application Considerations For Gold and Silver Wire Bonding Finishes

By E Probasco

GB3_2040_100dpi6x4Wire bonding is a method in which connections are made between components and/or the leads of a lead frame with extremely fine wires. The wires are typically aluminum or gold, but also include copper and silver. There are three common types of bonding, thermocompression, thermosonic, and ultrasonic. wirebond1Thermocompression uses force, time, and heat to join metals together, while thermosonic uses force, times, heat, and sonics, and ultrasonic bonding uses force, time, and sonics. In any of these instances the most important aspect of bonding is to form a good metallurgical bond with the wire and the metal substrate. Continue reading

Gold Plating of Micro Components Requires Specialized Techniques to Ensure Consistent Deposition and Part Cleanliness

By M. Lindstedt

Gold Plating - Interconnect Crimp Tubes

Gold Plated Interconnect Crimp Tubes

Gold plating of micro-components such as those used within the medical and interconnect industries presents unique plating challenges. Many micro-component surface treatments, whether being gold plated, silver plated or even passivated corrosion-resistant alloys require specialized process tooling and processing techniques to ensure plating finishes are uniform across all functional surfaces. The cleaning, processing, rinsing and drying processes must all be engineered around the characteristics of the micro component.

Prior to developing micro-compatible processes, plating techniques were limited to significantly larger components on a more macro-scale. Opportunities to expand services within the medical and interconnect industries was the business driver that pushed Advanced Plating Technologies (APT) to focus on process development for substantially smaller micro-components. Continue reading

Stringent Process, Tooling and Inspection Requirements Essential for Medical Grade Gold Plating

By M.  Lindstedt

Gold Plating Services – Delicate and Micro Parts
Gold plating services within the medical, electronic or telecommunications markets often involves the application of gold deposits on very small or micro parts.  In these industries, there is an on-going emphasis on Swiss and micro machining of smaller and gold-bars1 smaller components to meet design requirements.  In turn, the metal finishing supplier needs to be able process increasing smaller parts when processing these components. The technique of gold plating delicate and micro parts involves more than just the gold plating process.  The metal finisher needs to be able to clean, rinse, dry and inspect the deposits on these difficult components as well.  As such, the job shop needs to utilize not only the proper process method but have adequate line and inspection equipment to properly plate delicate and micro parts in gold. Continue reading