Risk of galvanic corrosion of dissimilar metals and matching connectors

When SAMTEC selects a connector for your application, it is important to select a companion connector with a similar plating material in the contact area. Different metals in the contact area can cause galvanic corrosion. Galvanic corrosion is an electrochemical process in which when two metals come into electrical contact in the presence of an electrolyte, one metal preferentially corrodes the other.

The figure below shows how different electroplating materials react with each other in terms of their potential. The greater the absolute value at the intersection of two electroplating materials, the greater the possibility of galvanic corrosion. If the number is highlighted in green, the material combination has a low current potential and is preferred. If the numbers are highlighted in yellow, the combination is not optimal, but is still acceptable. If it is not highlighted, the potential is high and you may not want to use this combination.

Plating options on connectors:

Most PCB-grade connectors are either gold-plated, tin-plated, or have selective gold/tin. Designers often ask us which plating finish we recommend. There are many considerations to consider (as evidenced by the variety of plating options on most basic connectors), but the best plating surface finish meets your system requirements at the lowest cost. In other words, make sure it works and meets your quality design specifications, but don’t over-engineer the plating.

Gold is usually specified for high reliability, low voltage or low current applications. Gold is used in high cycle applications because it is rugged and has excellent wear resistance (this is an example of a high cycle connector).

Tin is a lower cost alternative to gold and has excellent weldability. Unlike gold, tin is not a precious metal. The tin plating begins to oxidize the moment it is exposed to air. Therefore, the tinning contact system requires a larger normal force and a longer contact wiping area to break through this oxide film. Hopefully this video shows you what I’m trying to explain. The connectors shown are SSW series.

Validating the Performance of Miniature Array Connectors

Small, complex, and portable applications (in industries such as military/aerospace and medical) require miniaturized, reliable interconnects. As traditional surface-mount and through-hole interconnects reach their limits in terms of density and the number of signals that can effectively be used, many product designers are implementing high I/O array styles of interconnects. In a new white paper from Samtec, “Improved Solder Joint Integrity for High-Density Interconnect Applications,” the authors, Robbie Huffman and David Decker, detail the design characteristics and verification testing used to validate the robustness of the solder joints as well as the signal integrity in these next-generation board-to-board (B2B) surface mount area arrays (SMAAs).

While pin-in-ball SMAAs have been widely used in the industry for decades, they have lacked IPC classification. The demand for B2B SMAAs compatible with IPC-A-610 and IPC J-STD-001 Class 3 acceptance criteria is increasing as these types of interconnects are necessary to advance the state of the art for space-constrained applications in areas such as medical and military/aerospace design. The work in this paper shows that next-generation grid array interconnects meet the solder joint reliability and signal integrity performance required to support these high-reliability high-speed applications.

The white paper steps through detailed analysis of the new SMAA connectors, including improved automated x-ray inspection (AXI) as well as reliability testing per IPC-9701 and EIA-364-1000 test methods. The analysis includes both pin-in-ball and non-solder ball versions.

The tail of the next-generation pin-in-ball grid array component incorporates a fully plated, rounded, and coined bottom with contoured sides for increased robustness and an attached collapsible solder ball (Figure 1). These components are typically soldered to round land patterns. Samtec also offers non-solder ball versions, which use the same tail style but are soldered with increased solder paste volume in lieu of an attached solder ball (Figure 2).

The contoured tail style allows deeper tail penetration and an increased solderable surface area with signal integrity performance that supports data rates up to 112 Gbps PAM4 (56 Gbps NRZ) with robust and reliable solder joints that meet industry standards.

Bringing Vision to the Smart Factory

Embedded vision systems are becoming part of everyday life.  The development of autonomous cars has caught the headlines, and the use of visual systems will play a key role in their future success.  Embedded vision will be combined with other sensors to provide guidance for the vehicle.  Systems such as lidar (light direction and ranging) will measure distance, and the embedded vision systems will provide object recognition.  With this technology, the vehicle will be able to identify potential obstacles and react accordingly. 

The automotive industry, with its headline-grabbing developments, represents the most public example of embedded vision systems for collision avoidance.  However, the same technology has a range of applications in the industrial world.  As operators are employing more autonomous robots in the factory environment, the need for collision avoidance grows.   Embedded vision systems will allow factory robots to identify potential hazards and act in the most appropriate way.  This will keep the factory safe whilst maintaining the best possible efficiency. 

Keeping Everyone Safe

Embedded vision systems also have applications with the area of machine safety.  The task of providing safe working areas continues to grow in complexity as manufacturing plants become more flexible.  Not only do machines have to detect possible hazards, but it is also vital for them to understand the nature of the hazard in real time so that the right action can be taken to prevent accidents.  It is only with the sophistication of modern embedded vision systems that this has become truly possible.

Embedded vision systems also bring benefits to the efficient production line.  On any production line, one of the key tasks it quality control.  If the only source of quality control is manual inspection, manufacturers are forced to choose between random sampling or 100% inspection.  The first method tries to predict the quality of the entire batch based upon a random selection of products.  This is process introduces fewer delays but can risk the release of faulty products if the sample is too small.  The alternative – 100% inspection – is considerably slower and therefore makes the process more expensive.

Integration into the Smart Factory

As a solution, the sophistication of modern embedded vision systems allows automated, 100% visual inspection.  Each item can be imaged by a dedicated camera and its dimensions compared to the standard in real time.  The result is that faulty products can be identified immediately and discarded (or retained for further analysis).  This immediate inspection also provides important data that can be used to understand maintenance needs and even predict future failures. 

This use of data is at the heart of the smart factory concept.  For example, vision systems might identify a rising trend in faults from a molding machine, which could suggest the need for corrective maintenance.  This information can be correlated with other data collected from the same machine, including temperatures and energy consumption.  By analyzing all the associated data, the maintenance of the machine can be planned before a major failure occurs, which in turn minimizes the disruption to production.

New Applications

Embedded vision systems are continually being developed to make them smaller, more cost effective and more capable.  Their ease of use makes them an increasingly effective solution for a wide range of applications in the smart factory, from logistics to safety.  They will form part of the factory network and share data to increase the integration of all systems. 

Samtec manufactures a range of connectors that are ideal for the data requirements of the smart factory.  From high density, board-to-board connectors like the AcceleRate® family to high-performance RF connectors, the Samtec range has a fantastic selection of connectors that are ideal for the integration of embedded vision systems. 

Microwave, mmWave Connector Systems Achieve Excellent Performance

Magnum RF™ Ganged SMPM – mmWave

The first demo board highlights the board-to-board capabilities of our Magnum RF™ product line. Magnum RF is a multiport solution that incorporates an SMPM interface into a single housing allowing for density not possible with individual SMPM connectors.

Specifically, we see a Samtec Magnum RF edge launch, mated in a perpendicular configuration with a vertical, solderless, compression mount GPPC series.

Looking at the measurement results, we see insertion loss plots with the raw data at a maximum of -4 dB. Looking at the VSWR, we see a stable connection with a maximum of 1.5 VSWR up to 40 GHz. We’re measuring the two-piece, perpendicular connector system and the two PCB traces, at about 1” each. 

Magnum RF™ Ganged Cable – mmWave

The second demo is a Magnum RF cable assembly system. In addition to improved density, this ganged cable assembly provides a more secure connection to the mating connector with the housing, preventing any external forces from reaching the individual SMPM positions.  

This consists of a Magnum RF edge launch connector and a GC47 cable assembly.  Again, Magnum RF is ganged SMPM connectors. This is ideal when space is limited and a high operating frequency is required. 

Looking at the measurement parameters of the edge launch connector and .047 low loss mmWave cable assembly, the IL is under -5 dB at 40 GHz, and the VSWR is about 1.4.

2.40 Solderless, Compression Mount Edge Launch

Next, we have two solderless, compression mount 2.40 mm edge launch connectors, on the same PCB, connected by a 2” trace. Compression, edge launch connectors are the answer when the best VSWR is required for your application. 

For the full transmission line we’re looking at a maximum insertion loss of -6 dB at 50 GHz. The VSWR remains at 1.2 to 50 GHz.

2.92 Solderless, Compression Mount Edge Launch

And finally, in the same configuration, we have two solderless, compression mount 2.92 mm edge launch connectors, with 2” of trace. 

Once again, we see strong results: the insertion loss to 40 GHz, for the full channel, is less than -4 dB, and the VSWR is a maximum of 1.3, to 40 GHz.

Also, the orange cables used in this demonstration are Samtec’s new line of next-generation phase stable microwave coax. They provide improved stability and flexure over time, compared to typical coax cables. We’ll be telling you more about these orange cables soon. 

Which plating option is best for my connector?

Choosing the right coating is critical to the success of your connector system. Electroplating can affect the performance, life cycle, quality and cost of connectors.

The main costs of the connector are the plastic body, the pins, the plating on the pins, the labor to assemble it, and the packaging. For most connectors, the larger items are pins and plating.

For example, on micro-pitch, high-density interconnect products, pins and plating can account for about 25%-30% of the total cost of the connector. But on the basic 2.54mm centerline terminal strip (” pin holder “), it can account for 60%-70% of the total cost of the connector.

This is because the relative size of the plastic body on a miniature, mould-to-position miniature connector is almost always larger than the body basically cut into place on a strip-line connector. And, of course, if you use gold plating, the pins will cost more.

As I mentioned in my previous blog, I can’t speak for all connector companies when it comes to cost. Most of the examples I’ve used here have to do with Samtec interconnect, but I bet these principles apply to other connector companies as well.

What do we recommend?

Designers often ask us which plating finish we recommend. There are many considerations to consider (as evidenced by the variety of plating options on most basic connectors), but the best plating surface finish meets your system requirements at the lowest cost. In other words, make sure it works and meets your quality design specifications, but don’t over-engineer it on plating.


Gold is usually specified for high reliability, low voltage or low current applications. Gold is used in high cycle applications because it is rugged and has excellent wear resistance (this is an example of a high cycle connector). Our gold is alloyed with cobalt, which increases the hardness. We also recommend using gold in harsh environments, as it will remain free of oxides that can cause an increase in contact resistance.

Gold is a precious metal, which means it doesn’t react much to the environment.


Tin is a lower cost alternative to gold and has excellent weldability. Unlike gold, tin is not a precious metal. The tin plating begins to oxidize the moment it is exposed to air. Therefore, the tinning contact system requires a larger normal force and a longer contact wiping area to break through this oxide film

On top of that, tin is better suited for applications with fewer cycles because of the extra force exerted on the contacts, and simply because it is a softer metal.

Normal force

The difference between gold and tin comes down to the normal force. Compared to tin, gold requires a much lower normal force. Fine-pitch connectors do not have room for relatively large, thick contact beams with high deflection; This is necessary to produce the normal force tin required for tin-plated contacts.

Therefore, due to the physical size limitations of miniature connectors, gold is usually the only option. In other words, we use tin if we can. Tin is used in connector contact areas where appropriate normal forces can be generated and in benign environments. Tin oxidizes, so higher normal forces and contact wiping are required to break through the inherent oxide layer. Again, check out the video above.

Optional gold + tin plating options

Selective gold-plated tin is Samtec’s most popular plating option because it offers designers the best of both worlds. The contact area is the key area for contact and terminal pin interface and transmission signal, with gold reliability. The tail welded to the circuit board has the low cost and weldability of tin.

Tin lead, sparkly gold palladium nickel

Of course, other plating options are also available for specific applications. Two common examples include tinned lead and glitter palladium nickel. Tin lead is used in military applications and its advantages include low eutectic temperature, and the presence of lead inhibits tin whisker formation. Palladium nickel for extremely high cycle applications. However, for most typical applications, gold, tin, or selective plating will work fine.

Quick summary

Gold for high reliability, high cycle, low voltage applications.

Tin is used for applications that have fewer cycles, are cheaper, and can accommodate solder.

Selective plating, using gold in the contact fitting area and tinning at the tail, is usually the best choice.

Understanding IPC Class 2 vs Class 3 Solder Joints

In the manufacturing world there are standards for just about everything, and they all are typically there to ensure a product can perform as expected for the end application. Among these standards is IPC-A-610 covering solder joints for varying types of connector termination styles.

we are going to take a quick look at IPC-A-610 Class 2 and Class 3 solder joints, and some of the requirements of those two classifications. To narrow the focus further, we are looking at a J-Lead solder joint exclusively.

What is IPC-A-610?

IPC-A-610 covers the “Acceptability of Electronic Assemblies,” and more specifically for this blog we will look at the requirements for J-Lead solder connections. Since varying applications have different requirements, IPC has different classes and what a solder joints must look like to meet those class requirements.

Class 2 (J-Lead Components)

Class 3 (J-Lead Components)

Many of Samtec’s products can meet IPC-A-610 Class 3 which is normally required when a product must have continued high performance in extreme / harsh conditions. Mil / Aero and Medical applications typically require Class 3 products.

Class 3 increases the requirements in most areas of inspection for the solder joint over Class 2. The solder thickness (5) requirement remains “not specified,” and the side joint length (6) are the same as Class 2, but many of the other specifications have increased requirements.

For instance, the side overhang (2) and end joint width (3), are tightened in both directions by 25%. The side overhang is lowered to a 25% maximum of the width of the lead (4), and end joint thickness (3) is increased to a minimum of 75% of the lead width (4). While this may not seem to be a huge increase, it does add to the difficulty of producing a conforming product.

Insulation Resistance and Dielectric Withstanding Voltage Testing

That’s shocking! Insulation Resistance and Dielectric Withstanding Voltage are two of the qualification tests that Samtec performs in-house during part qualification testing.

These tests will ensure that when a connector is used in environmental conditions at the rated working voltage (de-rated from the test voltage) the product will not fail, and there will not be current leakage.

Insulation Resistance Testing

The purpose of the Insulation Resistance (IR) test is to determine the resistance of the insulation materials to leakage of current. This is measured on the surface while DC potential is applied at 500 VDC. 

There are several variables that can cause a part to fail prior to its calculated results; condensation on the part,  a crack in the body, and damage to the insulation.

Samtec tests it parts according to EIA-364-21 “Insulation Resistance Test Procedure for Electrical Connectors, Sockets, and Coaxial Contacts.”

Dielectric Withstanding Voltage Testing

The Dielectric Withstanding Voltage (DWV) test is intended to take into account momentary over potentials caused from switching, surges,and other phenomenon. This establishes the proper operation at a test voltage that is three times the rated working voltage of the system under the test. 

DWV is determined from the breakdown voltage (BDV) of a part (DWV = 0.75 x BDV). The BDV is the voltage where the part arcs across the metallic interface; think pin-to-pin or pin-to-hardware, and working voltage is = 1/3 x DWV or 0.25 x BDV.

For example: if the breakdown voltage is 1000 VAC the Test Voltage will be 750 VAC, and Working Voltage will be 250 VAC.  DWV is tested by applying the calculated test voltage for 60 seconds.  The part will pass if there is no indication of arcing. 

For DWV, Samtec uses EIA-364-20 “Withstanding Voltage Test Procedure for Electrical Connectors, Sockets, and Coaxial Contacts.”

Why test IR/DWV?

Bottom line, IR /DWV are part of determining a connector’s performance in varying conditions.  The test sequence for both IR/DWV involves using thermal shock and humidity cycling.  By testing under these conditions, Samtec is confident that its parts will perform in less than ideal environments.

The Diverse Connector Market

The connector marketplace is one of the most diverse and interesting in the entire electronics industry.  The roles that connectors are required to play range from the smallest data connections to the largest power supplies.  They are frequently employed in some of the toughest conditions on Earth and despite this are expected to provide remarkable levels of reliability.  As a result, the industry has responded with a quite bewildering array of choices.

Gigat dump trucks are working in the mine for the production of apatite in the Murmansk region carrying rock. Extraction of minerals in the harsh highlands.

Many connectors are designed as solutions for particular markets.  When faced with the entire connector marketplace, we therefore often ignore certain connectors from our potential list of choices because we assume they do not cater to our own industry.  This is quite understandable as specifying a connector can be a little daunting.

Self-Imposed Rules

After a time, these assumptions can become rules that we create for ourselves.  However, when it comes to connectors, many of these rules can be broken.  When creating a new device, the key task for any engineer should be to pick the product that will best solve their design challenge, and as with many things in life there are often more ways than one to proceed.  If we ignore the rules and investigate products that we would normally disregard, there are surprising things we can learn.

This is not limited to the world of connectors, or even the electronics industry.  The largest tire manufacturer in the world is not Continental or Dunlop, it is the Danish toy company LEGO.  And who would have imagined that global giant Volkswagen makes more sausages than cars every year?  Although these examples are not of hugely practical value (unless you want a Currywurst sausage, in which case I can thoroughly recommend the Volkswagen product), the connector industry does offer some intriguing possibilities.

Looking Beyond the Perception

There are entire categories of products that were designed for one application but are suited for others.  I have been a long advocate for the use of automotive connectors in industrial settings. Connectors intended for use in vehicles have much to offer the industrial engineer.  They have been designed to survive the harsh conditions found in some of the most demanding environments, from extremes of temperature to contamination by mud and dirt. 

Automotive-grade connectors are designed for use in mass-produced vehicles, and they are made in huge quantities for the global market.  This makes them cost-effective and easy to obtain. It also means that the tooling and expertise needed to terminate them are both easy to find.

The automotive industry is not alone in its need for dedicated connectors.  The military and aerospace sector has always had a lot to say about the connectors it uses.  A significant number of connectors are created to provide the high performance demanded by the defense industry. They are made to work in tough conditions, which are not always limited to the battlefield. 

Geological instrumentation, industrial automation, commercial vehicles – the list of potential applications for which a high-performance connector might be suitable is virtually endless.  Engineers the world over need a connector that must be mated and unmated frequently, that will be exposed to wind and weather, or must be shielded against unwanted electromagnetic interference (EMI).  If any of these conditions sound familiar, then a connector designed to military requirements might provide a solution for you.

The Diverse Market

When it comes to choosing connectors, there is often a different way to achieve your goal.  The conventional view can make us assume that a particular product type will not be suitable for our needs.  But that same conventional view can stop us from seeing the tremendous innovation that occurs throughout the industry.

Do not let convention dictate how you choose connectors.  Allow your engineering needs to be the guide that leads you to a solution.  Be clear about the features you require, decide on the connector that suits your application, and ignore the rules. Make sure you look at our applications page to see what might inspire your next design

A New Angle On Power/Signal High-Density Arrays

Angles surround us every day – physical angles like the corner over there, and angles of perspective. Samtec’s new AcceleRate® mP high-density power/signal interconnect system was born out of a different perspective on power integrity and a 90 degree rotation.

Best in class density for a power/signal interconnect system, AcceleRate® mP achieves up to 240 I/Os in .438 sq. inches. It also packs a punch with up to 22 Amps per power blade and 56 Gbps signal performance.

SRotated Power Blades

AcceleRate® mP features power blades rotated 90 degrees, giving equal access to heat escape for uniform cooling and increased current capacity up to 20% compared to similar blade style pins. The breakout region (BOR) is also simplified, as this connector system is designed to maximize current capabilities and minimize distribution resistance in the same form factor, ultimately reducing current crowding.

Design Flexibility

This high-density, multi row design is open-pin-field for grounding and routing flexibility – up to 240 signal pins in 6 rows and 4 or 8 total power blades in a low 5 mm stack height. Additional signal and power blade counts, plus stack heights up to 16 mm, are in development to accommodate a wider range of applications. Optional 10 µ” or 30 µ” gold plating on contacts with matte tin tail is available to meet specific regulations.

Ruggedizing features for AcceleRate® mP include alignment pins and through-hole weld tabs for a secure connection to the board. For assistance with blind mating, polarized guide posts are part of the standard connector body.

For more about power and signal integrity regarding AcceleRate® mP, check out this post.

AcceleRate® Family of Products

AcceleRate® mP is part of a quickly growing family of extreme density and extreme performance interconnects packaged in small form factors. Click here to learn more about other AcceleRate® products such as Flyover® cable assemblies, and other high-density board level connectors.

Samtec Expands ExaMAX® High-Speed Backplane Connector System With New DMO Options

Samtec supports orthogonal backplane architectures with new DMO options from within the ExaMAX® High-Speed Backplane Connector System.

Samtec ExaMAX® DMO Options

Samtec’s new ExaMAX® DMO solutions offer system designers flexibility by removing the mid-plane, allowing fabric cards and line cards to mate directly. This fast-growing system architecture increases airflow and improves thermal efficiencies throughout the chassis. DMO solutions enhance signal integrity via shorter trace lengths and fewer connector transitions while streamlining the system BOM and optimizing system cost.

Samtec’s ExaMAX® DMO system consists of the new EBDM-RA series which mates directly with existing EBTF-RA series. Currently both 6 pair x 10 column and 6 pair x 12 column solutions are available. Guide pin and screw mount options are also available. 6 pair x 6 column and 6 pair x 8 column options are under development.

“Next generation system designers are quickly adopting DMO architectures,” said Jonathan Sprigler, Backplane Product Manager at Samtec, Inc. “Leading equipment vendors from across the data center industry – storage, server, networking and other applications – are leveraging the advantages of DMO via Samtec’s new EBDM-RA series.”

Key ExaMAX® Technical Features

Samtec’s EBDM-RA series is but one solution from the ExaMAX® High-Speed Backplane Connector System. The ExaMAX® line of products is optimized for speeds up to 56 Gbps (PAM-4 modulation). Return loss compliance is achieved in both 85 Ω and 100 Ω systems due to targeting the 92 Ω specifications and controlling reflections at all geometry transitions within the connector.

ExaMAX® also has the industry’s lowest mating force with excellent normal force and meets Telcordia GR-1217 CORE specifications. With two reliable points of contact at all times, even when subjected to angled mating, residual stubs are minimized for improved signal integrity performance. A 2.4 mm contact wipe increases reliability while the hermaphroditic mating interface ensures stub-free mating and reliable alignment

The backplane system features individual signal wafers with differential pairs in a staggered design and arranged in columns with zero skew. Each wafer includes a one-piece embossed ground structure, which increases isolation to significantly decrease crosstalk.