APT BLOG

Benefits of Gold Plating

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The value of gold as a noble metal has been observed for centuries across a range of decorative, functional, and industrial applications. In an increasingly connected world, the benefits of gold plating are being utilized like never before for high reliability contacts and connectors to ensure rapid and reliable signal transmission. Since 1948, Advanced Plating Technologies (APT) has delivered gold plating services across an array of demanding industries, including the interconnect and medical sectors as well as the Telecommunication and defense industries.

As an ISO 9001 & 13485 certified and ITAR registered company, Advanced Plating Technologies provides gold plating services for even the most demanding applications. APT offers barrel, rack, and vibratory plating of loose-piece components in hard and soft gold as well as duplex gold plating.  APT offers 99.9% pure (Type III) soft gold and 99.7% purity hard gold (Type I or II) and can provide a range of underplate combinations to meet nearly any ASTM, Military or OEM specification. Continue reading →

Quick Guide to Copper Plating

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Copper Plating Properties and Applications

The process of copper plating involves the deposition of a copper layer onto different substrate metals for functional purposes as either an underplate or final finish. The element copper provides many excellent properties in that it is non-magnetic, antibacterial, and has high electrical and thermal conductivity.

As an underplate copper promotes both adhesion and corrosion resistance of the final finish. As a final finish, copper is used as a metallic lubricant or anti-seize coating on sleeves, bearings and fasteners. Copper is plated on steel fittings to promote soldering in HVAC applications; it is also used for weld stud/fastener applications to promote current transfer during the welding process.

Heavy deposits of copper plating are used as heat treat stop-off for heat treating of ferrous metals. In this application a deposit of copper between 0.001-0.002” per side is plated on a steel part and subsequently machined off of the surfaces to be heat treated. The exposed steel can then be nitride or carburized with the copper-plated surfaces remaining untreated by the heat treat process. After the heat treatment, the copper plating is stripped from the part leaving a final steel component with selectively hardened surfaces.

Examples and Applications of Copper Plating

As one of the most commonly used finishing metals, copper plating is used for a range of applications, including:

  • Underplate for other finishes such as nickel or tin
  • Brazing or soldering applications for steel and stainless-steel components
  • Weld studs and welded fastener applications
  • Heat treat stop-off for ferrous metals
  • Jacketing for projectiles within ammunition industry
  • Metallic lubricant and anti-cease coating for bearings, sleeves or fasteners
  • Electro Magnetic Interference (EMI) and Radio Frequency Interference (RFI) shielding
  • Conductivity for Eddy Current and Variable Frequency Drives (VFD)

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A Discussion of Metal Finishing & Environmental Stewardship

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Metal Finishing Environmental Stewardship Benefits More Than Just the Environment

Advanced Plating Technologies has always taken a clear stance on the environment.  Since the beginning of the clean water act in 1972, APT has been committed to not only meeting but exceeding all local, state and federal environmental laws.  This record speaks a silent assurance that many “low cost” metal finishing suppliers cannot.  In fact, metal finishing companies with substandard environmental systems is a liability not only for their continued operation but for potential litigation down the road against themselves and their customers.

Surface Finishing Waste Treatment Facility

APT’s Modern Waste Treatment Facility

The metal finishing industry continues to be one of the most highly regulated industries in the country with new regulations and requirements added each year.  New regulations on PFOA and PFOS compounds and additions to the Toxic Substances Control Act (TSCA) are just a few of the latest impending regulatory restrictions. For this reason, APT continues to invest in improved treatment technologies and self-imposed compliance standards below permit levels as an example within the Industry.  APT’s leadership has been recognized with numerous local, state and national environmental awards from the Milwaukee Metropolitan Sewage District (MMSC), Wisconsin State Department of Natural Resources (DNR) and the United States Environmental Protection Agency (EPA).

The history of environmental compliance within the metal finishing industry is marked by various landmark laws that have far-reaching implications counter to what many would consider sound environmental practices.  In 1980 the Resource Conservation and Recovery Act (RCRA) mandated that the F006 wastewater treatment sludge produced by electroplaters shall be listed as hazardous waste categorically. This designation was applied without testing the waste product for its actual chemically hazardous profile using the TCLP methodology.  Thus, the applied arbitrary designation limits the ability of the waste to be recycled to recover the valuable metals contained therein. Since then, this legislation has come under increased criticism from many in the industry as it results in the waste of thousands of tons of valuable metals each year. Continue reading →

Firearm & Firearm Component Finishes – What You Need to Know

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Firearm Component Finishes

When it comes to selecting a black finish for your firearm or firearm component there are several key features you need to consider. When going through options you need to ensure your firearm finish can meet several key characteristics such as the ability to hold tight tolerances, provide enhanced lubricity, wear resistance, corrosion protection, and, of course, provide a uniform and consistent black appearance.

Advanced Plating Technologies has worked hand-in-hand with numerous firearm OEMs throughout the years to provide a superior black finish that meets all the above requirements. Tacti-black® HP+ was developed in response to feedback received from numerous firearm OEMs that needed a finish that could meet all of the above requirements on a range of materials including steel, stainless steel, and aluminum.

A Firearm Finish for Any Base Material tactical black firearm finish for Lower Receiver

Unlike common firearm coatings such as black oxide, nitriding, anodizing, and QPQ, Tacti-black® HP+ is “material blind” meaning it can be plated onto any metal material. This tactical firearm finish is perfect for a large array of firearm components like custom lower receivers, trigger sears, hammers, and stamped magazines.

APT can provide this proprietary tactical firearm finish to most any metallic substrate from CNC firearm components to 3D printed and MIM alloy components with a density of over 90%.

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Solderable Gold Plating of Electrical Contacts

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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

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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Silver Plating of Copper or Copper Alloys

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Silver Plating of Copper or Copper Alloys – Silver Properties

Silver plating of copper or copper alloys is a highly functional finish for transferring heat and electricity utilized across a wide breath of industries.   Silver has been applied since late 1800s on electrical switchgear and other components that pass electrical current.  In recent years silver plating of copper electronic components including connectors and terminals has grown rapidly within the electronic, automotive and electric vehicle (EV) markets.  Silver plating has many unique properties that make it desirable for these applications. The primary reason is that silver has the highest electrical and thermal conductivity of any metal, which facilitates the efficient transmission of electricity and heat.  In addition, silver is a relatively soft metal which allows the silver deposit to compress and form around a mating connecter filling small voids and micro-roughness. This increases the effective contact area resulting in less overall connector resistance.

Conductivity of Silver as Compared to Copper and Other Metals

Figure 1: Conductivity of Silver as Compared to Copper and Other Metals

Silver has excellent lubricity and resists galling in switching, sliding or rotary applications.  However, high-pressure wear surfaces such as blade-style stab connectors can be susceptible to silverwear. In applications such as this, a higher deposit thickness of silver is recommended as well as the use of a nickel or electroless nickel underplate.  Thinner silver plating without a nickel underplate is best used on static joints or low duty cycle connectors that are mated and unmated relatively infrequently.

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Nitric vs Citric Acid Passivation

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Nitric vs Citric Passivation Methods

Stainless steel is an inherently corrosion resistant material, however when stainless steel is machined, formed or fabricated free iron can be introduced to the surface that can corrode independent of the base material.  Proper passivation of stainless steel with an oxidizing acid such as nitric or citric acid removes this free iron and promotes the growth of a thin, dense protective oxide layer which maximizes the corrosion resistance of the stainless steel. Depending on the type of stainless steel and end application certain passivation processes may perform better at passivating than others. In this article we will compare nitric vs citric acid passivation which are the two primary chemistries specified in ASTM A967 and AMS 2700.

Nitric Acid Passivation

Passivation Specifications

When comparing nitric vs citric passivation, the most common method used throughout industry is nitric acid passivation. The Nitric acid passivation processes was the original passivation processed specified in QQ-P-35, the first military specification covering passivation, revision A being released in the 1960s.  Nitric acid passivation offers a range of options to customize the oxidizing potential of the acid to suit a specific grade of stainless steel. The various methods and types of nitric acid passivation include several heated options as well as options that include a sodium dichromate.

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Gold Plating Thickness of Connectors

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Gold Plating Thickness of Connectors and Contacts gold 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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Silver Plating on Stainless Steel and High Temperature Alloys

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Silver Plating of Stainless Steel – Silver Properties

Silver plating on stainless steel and other high temperature alloys such as Inconel®, Nitronic® and Hastelloy® is a common silver plating service for nuts, fasteners, slip-rings, thrust-washers, bushings and other bearing surfaces that benefit from the lubricity of silver at high temperatures allowing parts to exhibit anti-galling and anti-seizing properties.  Silver is a unique precious metal that exhibits many desirable properties for utilization across a broad range of engineered applications. Of all metals, silver has the highest thermal conductivity, electrical conductivity, and optical reflectivity in the visible portion of the electromagnetic spectrum; silver has outstanding temperature resistance with a melting point of 962° C (1763° F). Additionally, silver is a soft, ductile metal with good embeddability that performs well under high torque and loads.  Silver also provides excellent solderability and brazing characteristics for joining applications of stainless steel and other high temperature alloys.  The unique combination of lubricity, high temperature resistance and thermal conductivity make silver plating on stainless steel and other high temperature alloys an outstanding combination for high temperature fastening or bearing applications where heat transfer high temperature lubricity are the principle design considerations.

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

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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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