blog posts related to probes or connectors

Connector Design Considerations for the Demanding Medical Market

Challenging environmental conditions and high reliability requirements create the need for can’t fail connectors.   This article explores some of the more critical design factors that go into designing a new connector for the medical market.

The medical industry requires connectors to reliably operate in a variety of harsh environments.  This drives the connector design to be custom, specifically addressing each application’s unique challenges.  There are many attributes that must be considered when laying out a connector’s specifications, but they typically fall into 1 of 3 categories: material selection, mechanical properties and electrical specifications.   All 3 categories must be considered concurrently to yield a successful connector design.

Material selection

Proper material selection will be determined by the environmental conditions the connector must operate in and is often driven by regulatory acceptance requirements.  These factors must be considered from project inception and throughout the entire development process.   Factors can range from flame rated plastics (UL, Vx rated) to chemical resistance.  Chemical sensitive applications may require plating structures that resist harsh chemicals and balance contact life on both sides of the connection system with the electrical requirements.  Base metal selection can also affect connector reliability.  Compliant contact designs with a capability to self-clean by implementing a scrubbing action can also influence material selection.  The development process must also consider materials that are favorable for prototyping, and that can later be scaled into molded form factors when the project reaches high volume production.  Using the proper materials in the prototyping phase can allow design validation prior to the expense of fixed tools, reducing technical risks, and the commercial risks from a delayed program.

A healthcare application with a portable device dock provides an example where all the considerations will play a role.  The stability of the insulator and reliability of the contacts in such a device can be stressed by common field processes such as using beach wipes to clean, or real-world threats like a spilled beverage.   Planning, design and validation provide the best path to avoid a failure or costly pattern of failures.

Mechanical properties

Choosing the contact element type is probably the single most important decision for any connector design.  Spring probes, also known as or Pogo® pins, have proven to be the most reliable means of making contact when thousands of cycles are needed.   The compliance aspect of spring probes also compensates for non-planarity challenges between the contact surfaces as well as blind mate applications.  For portable, wearable or base charging applications, the challenge can simply be maintaining continuity in a dynamic environment.  Shock and vibration tolerant connectors are necessary for rugged environments.   Spring probes are offered in a variety of spring forces and tip geometries, tailored to the application.

Probe architecture is critical when designing the optimum solution.  Probes with a deliberate bias offer the most stable design to transmit power and data.  The mechanics of how to achieve the bias affect; contact resistance, cycle life, signal stability as well as cost are essential elements to a successful probe design.  The available space and required usable stroke of a probe will also dictate internal probe design.

Electrical specifications

The number of signal contact points and layout pattern is typically the first design parameter to consider.  If the signals operate at high frequencies (>500MHz), then multiple ground pins may be needed to ensure proper signal integrity through the connector. With the advent of increasing data streams, and more capable transmission standards like USB2.0, it is more important than ever to understand the influence of an electrical contact.  A qualified solutions provider must be able provide design, simulation, and then validate data transmission through extensive testing.  Many of today’s medical connectors operate at high voltages and high currents.     Contacts must be designed to the electrical specifications needed to achieve the products functions such as cut and cauterize, or micro fluidic control.

In summary, when designing a connector for medical applications it is important to equally consider the materials, mechanical properties and electrical characteristics of the design to ensure a successful product.

Learn more about Xcerra’s connectors solutions: click here

Flat Probe Technology for RF Test

Today the semiconductor test market is very competitive. This is especially true in the consumable contactor market.
Low operating costs and low average selling prices create low barriers to entry. Micro-organizations plants themselves next to their sole customer and provides fast turn times at competitive prices and onsite support. Although this is acceptable for some it is a risky business model. Furthermore the depth of knowledge of the product and therefore the value add from these micro-organizations is limited.
Outsourcing components can diminish the value add of the end product and lead to finger pointing and delivery delays. These factors push organization toward more stable and established vendors that can not only provide fast turn times and good support but they can focus on R&D and new product development.  The ability of these organizations to fund R&D has resulted in revolutionary “flat probe” technologies that combine both electrical and mechanical performance at a significantly lower cost point than traditional radial spring probe technologies.

Larger spring diameters allow more force with less spring length allowing shorter and narrower probes than possible with radial technology. Furthermore the external plunger surfaces allow superior plating than in the internal surfaces of a barrel. Hard base materials offer longer life with lower contact resistance. Finally, with proper attention to the “guts” of the probe design, flat probe technologies can be used for high frequency semiconductor test applications. This presentation will introduce various flat probe technologies and compare and contrast their designs against other flat probe technologies as well as against radial probe technologies.

Download the presentation of Jason Mroczkowski, Director RF Product Development and Marketing IPG, which was awarded “Best Tutorial” at BiTS 2017:

Download the full presentation

 

Choosing the Right Spring Probe for ICT and FCT Testing

How do I select base material /plating , spring force, and tip selection? In the world of spring probes, choices abound when it comes to selecting materials and platings for plungers, barrels and springs. Choosing the right options can greatly impact yield, probe life and cleaning frequency.

Base Materials

BeCu is a popular choice for both plungers and barrels and has outstanding mechanical properties with high electrical conductivity. Steel is significantly harder and is typically used for plungers with aggressive tip styles. Nickel Silver is very resistant to corrosion and is well suited for barrels. Bronze has good wear resistance, cold formability and high electrical conductivity. Lastly, brass is a high quality material with high electrical conductivity and good wear resistance.

Plating Choices

Choosing the right plating depends on the application and customer preference. Gold is widely used and provides excellent electrical performance and good corrosion resistance. To address lead free solder challenges, ECT has developed a proprietary plating material called LFRE which is approximately 5 times harder than gold.  LFRE plated tips are much more durable and wear resistive than gold and have proven to last more than twice as long as gold plated probes. LFRE probes are also less susceptible to solder and material transfer and require less cleaning than gold plated probes.

Spring Force

Spring force selection is mainly dependent upon the application. It provides the required compliant force at the plunger tip and the contact force between the barrel and the plunger. Higher spring forces provide more effective penetration through contamination contact points, but leave heavier witness marks on the test point. Lower spring forces should be used where no witness marks are welcome or to prevent board flexing on higher pin count applications. Stainless steel must be used for springs when test temperatures exceed 100°C.

 

Tip Selection

Most tip styles can be used for a variety of different applications. However, some test targets are better suited for unique tip styles. Some applications require a non-aggressive tip to be used on pads, such as radius, crown, or flat. These tips leave little to no witness marks on test pads. For through-hole vias ECT offers: blade, star, or pyramid tip styles. These are well suited for contact through the outer ring of the via surface. Over time solder builds up oxide layers, therefore medium to very aggressive tips like the serrated, crown, blade, pyramid and point are used. Posts, pins or screws are more unpredictable and therefore more challenging. For these applications, tip styles like the cup, serrated and crown are best suited. Other applications may require more unique tip styles depending on test target material, size, shape, access and cleanliness. With over 50 years of making high quality spring probes, ECT has developed a vast library of probe options for all your testing needs.

Product Selection Made Easy on shop.ect-cpg.com

The new e-shop provides sophisticated filters to make your product selection as convenient as possible. Use this button
Make Your Selections Online
to learn more about the ECT offerings for ICT / FCT test or download the overview of the probe offerings for ICT/FCT test of Everett Charles Technologies here
Download the ECT ICT/FCT Test Offerings

 

RF requirements and spring probe development for semiconductor test

High bandwidth,  low inductance signal paths are essential for testing next generation RF  devices.    A successful test strategy must start with  consideration of  contact technology  used to interface the device lead.   Spring probes are the technology of choice for most applications when considerations also include mechanical reliability.  The ZIP flat probe technology from Everett Charles Technologies will provide the case study for the article.

This article will begin by exploring present and future RF device requirements’ linking several RF device applications with their critical high speed electrical test requirements.

The vast array of semiconductor applications translates into an equally diverse set of challenges for test engineers. However, there are two constant drivers that permeate the industry: smaller pitches and higher signal integrity. High bandwidth signal paths and low- inductance power delivery are essential for testing the next-generation of RF devices.

Several factors can impact signal integrity, such as contactor and performance board design, and material selection. However, a successful test strategy must start with consideration of contact technology used to interface the device lead. Spring probes are the technology of choice for most applications when considerations a lso include mechanical attributes such as reliability and wear, as in high-volume test applications. An effective spring probe design must address the balancing act between electrical and mechanical performance. Developing a spring probe capable of 40Ghz+ bandwidth (@ -1dB) while providing adequate spring force and compliance, not only involves extensive electrical and mechanical simulation, but also advanced manufacturing techniques.

Read the full article here