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.

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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

 

5G: Plunging into open-ended test requirements

Mobile broadband technology is beginning to crawl from commonly known 4th Generation Wireless (4G) transmission standards to fifth generation wireless IMT2020 standardization, also known as 5G. This 5G network technology will influence semiconductor test in two directions, an evolutionary track and a revolutionary paradigm shift. The revolutionary aspect of 5G targets massive amounts of bandwidth not previously thought of as accessible. Many technological challenges have blocked the reasonable implementation of 5G cellular technology. Consumer demand for rapidly growing amounts of bandwidth, has created the need to solve these challenges.

Recent millimeter wave (mmWave) band spectrum studies have put the solution for 5G in reach with large amounts of spectrum available in mmWave. Frequency bands under consideration include 28, 37, 39, 64-71, 71-76, and 81-86GHz, which are far removed from the less than 6GHz technology offered today. Shifting from 6GHz to 28GHz and beyond creates challenges up and down the value chain. This fundamental shift is why many data compression techniques currently in development will become the next evolutionary step towards 5G, also referred to as 4.5G. The techniques for 4.5G focus on better access within currently defined licensed spectrum.

R&D activities in studies beyond 6GHz frequency bands have been restrained because of the mmWave characteristics of limited transmission and wavelength. Studies on standards beyond 6GHz have lived in academia and the military but had limited consumer application. With limited consumer application there was not a great wave of interest in 5G as an acceptable standard. So, what has changed? Consumer demand for more bandwidth which is faster, smarter and less power hungry at a low cost!

Research from NYU Wireless, Ericsson, and many others has driven proof-of-concepts for mmWave applications to acceptable levels of reasonable realization. Areas of research interest include enhancements to the physical layer, interference mitigation, multiple-input-multiple-output (MIMO) antennas, network security, network management and many others. Bridging the gap and creating a learning environment is automotive radar and wireless LAN 802.11ad (also known as WiGig) specification standards. Both standards exist with promising levels of acceptance which drive the need to test semiconductors in the K-Band, and the V & W bands of mmWave cellular channels. Is there one key research breathrough which will put realization in hyperspace?

Since we are discussing a standard that is not yet ratified and the test requirements are not fully known, we must extrapolate to hypotheses based on Xcerra’s years of experience in RF test. This future technology has driven all of the semiconductor test equipment suppliers to rethink the world of RF test. Using our proven experiences in automotive radar and 60GHz WiFi we are applying what we have learned in this area to bring solutions to market. But creating the technology to test these devices is only half of the battle. These products have to fit within a model of production quality test while answering the requirements of mass production and aligning the costs associated with consumer expectations. How will the 5G revolution affect your business and testing operations?

Moving RF test from standard cable and pogo technology, which has been well understood for many years, to waveguides and Over The Air (OTA) connectivity is challenging. Waveguides create a new complexity where mechanical considerations are equal to RF signaling and measurement parameters. We have suddenly had to become plumbers to create and execute multisite test capabilities. For OTA testing, we are now required to speak the language of horn antennas and linear arrays rather than screwing down a Sub-Miniature version A (SMA) connector to a device under test (DUT) board. The benefit of OTA testing is that it allows us to move quickly to multisite test capability without the complexities of creating expensive multisite waveguide connection schemes. Where this becomes a challenge is the mathematical models required to beam-form a signal to the appropriate site for measurement or capture.  As we move forward, test requirements will have to allow for the inconsistencies of sending and measuring signals through the air or accept the costs associated with mmWave. We all know where this is going to go! What role do you see OTA testing playing?

Over The Air test has changed transmission properties versus well known cable models. With the use of cables we have had the benefit of working with known properties regarding RF transmission, and when needed, can adjust for any inconsistencies along the signal path. One obstacle which is commonly taken for granted is the calibration of the Test system. Many systems today calibrate all inconsistencies without the user having to pay great lengths of attention. System calibration, user calibration, and de-embedding are commonly used today to ensure reliable, accurate measurements. Calibration and system to system stability at mmWave frequencies has all of us engineering new solutions for high-volume semiconductor production.

Lastly, we are all devoting time on the subject of Multi-GHz bandwidth requirements for the IF and RF for mmWave technologies. For starters, a 2.16 GHz bandwidth requirement for 802.11ad is driving semiconductor manufacturers, and back-end test suppliers towards a new horizon. Test instrument vendors, whether benchtop or production test, are making strides with up/down conversions to the 60 GHz mmWave band. Creating the 802.11ad modulation in IF is pushing sample rates beyond 1 Gbps, which is 4 times today’s 802.11ac standard. The issue with multi-gigabit sample rates is the heat created by the multichannel high speed ADC’s and DAC’s to achieve the 802.11ad modulation requirements.

In summary, paradigm shifts in our industry has created an opportunity that we are capitalizing on with our deep understanding of RF and mmWave. Our research in automotive radar test has given us the tools to move quickly towards broadband cellular 5G testing in the future. Expectations of production test in this arena will be realized in the near future. Therefore agreements to acceptable standards must be approached with a collaborative mindset between end customer, semiconductor supplier and test vendor, to achieve best practices for mmWave production test.

Is a final test solution for WLCSP devices needed?

Andy Nagy, Senior Director of Marketing for the Handler Group at Xcerra has recently published on article about final test of WLCSPs in Chip Scale Review. He describes the short-comings of the established test process for WLCSPs particularly with the wider adoption of these package types to critical applications. The article elaborates on a new process, which supports true final test the packages – right before shipment

 

Download the full article

Embedded Components in “Bare” Boards

In the past, the electrical test of bare printed circuit boards (PCB) and the test of populated boards were separate subjects and performed by very different types of test systems. With mobile products and wearables becoming more sophisticated and the internet of things, boards have become smaller and, as a result, board space is more limited than ever. This forces designers to embed some of the circuitry inside the PCB itself to maximize PCB surface area while creating as small a package as possible.

This started with simple, single components, like resistors, capacitors and inductances, and has moved on to whole systems-in-board. In the latter case, silicon devices are often soldered directly in the PCB. To develop, produce and test the PCB the designer, silicon and PCB manufacturer, test department and equipment manufacturer have to work together closely because where one area of responsibility begins, and another ends, has become imprecise. This also impacts the distinction between in-circuit test equipment and bare board test equipment, driving bare board testers to include features previously only found in in-circuit testers. This trend is likely to continue.

Today some of the bare board manufacturers have to produce and test new designs with embedded components on a daily basis. The resulting challenge of a de-facto in-circuit test on what once was a bare board is solved successfully by closely cooperating with both their customers and test equipment manufacturer. This type of cooperation will become even more important with future increases in complexity.

For further information, please check out the two following links. The articles are a bit older, but the predictions of the roadmaps still prove to be true.

www.ats.net/wp-content/uploads/2013/03/High-End-PCBs_Oulu_2013_handout.pdf

www.amkor.com/go/AmkorGSA-July2014-Article

Exploring Semiconductor Test Equipment Business Cycles

The semiconductor test equipment market has matured. You would expect an industry that came of age in 1980s would have matured over the last 35 years and in fact it has. The semiconductor test equipment industry has experienced consolidation, a sure sign of maturation. Two factors are important to consider with regard to it becoming a mature industry. First, market share shifts of 10 points or more are extremely difficult and slow to occur. The value of incumbency is very high and to achieve growth faster than competitors means uncovering new market opportunities through innovation of your existing products, applying existing technologies into adjacent or new markets, or through merger or acquisition.

A variety of technology and business trends impact the test equipment business cycles. In the full paper, which we invite you to download [hyperlink], we analyzed the impact of the following drivers n detail:

  • IC unit volume expansion
  • Equipment lead times
  • Seasonality
  • Degree of customization of SOCs
  • Chinese market
  • Replacement of home-grown ATE by commercial solutions
  • OSAT business model

Download the full paper

Forecast based on GDP growth?

Today, everybody in the semiconductor industry is aware of the substantial influence of the consumer. Behavior of end consumers in turn heavily influences the performance of the overall economy, which statistically is measured in the GDP. Recently IC Insights published a bulletin, which describes their findings examining the worldwide GDP growth and its impact on the 2016 IC market growth.

For the period from 2010 to 2015, IC Insights derives a remarkable correlation of 0.92 between the worldwide GDP growth and the IC market growth. Keep in mind that 1.0 would be a perfect correlation. If the correlation was relatively weak or even negative, IC Insights believes that the ongoing consolidation in the maturing IC manufacturer and supplier market together with other changes (e.g. a strong movement to the fab-lite model and a declining capex/sales ratio) would lead to a less volatile market.

With forecasted annual worldwide GDP growth rates that range from 2.7% to 3.1% over the next five years, IC Insights’ IC market growth rate expectations mirror the narrow range of worldwide GDP growth.

Read the full IC Insights bulletin “New 2016 McClean Report examines worldwide GDP growth and its impact on 2016 IC market growth” here:

http://www.icinsights.com/news/bulletins/New-2016-McClean-Report-Examines-Worldwide-GDP-Growth-And-Its-Impact-On-2016-IC-Market-Growth/

Semicon Europa 2016 Call for Papers is Open

Semicon Europa returns to Grenoble, France this year from Oct 25 – 27 and you are invited to respond to the Call for Papers for the technical sessions and presentations.  Technical presentation abstracts are due April 29.

Although there will be no European Manufacturing Test Conference (EMTC) at Semicon Europa this year, test challenges will be discussed during a dedicated session in the Advanced Packaging Conference (APC) to be held October 25 – 26.

Advanced Packaging has already seen widespread adoption in the consumer market, to enable the high functional integration we have come to expect in our smartphones and mobile devices.  Now Advanced Packaging is seeing wider adoption in industrial, medical and healthcare, automotive and even military and aerospace markets, to satisfy the seemingly contradictory requirements of Higher Performance, Reduced Form Factor and Lower Cost.  These Advanced Packaging approaches inevitably introduce a new set of Test challenges, e.g. how much test is required to verify a multi-die package has been correctly assembled without significantly increasing cost?  How will the latest generation of Advanced Packages be reliably handled and tested in high volume manufacturing?  Does the combination of functions enabled by Advanced Packaging, including MCU cores, embedded memory, wireless interfaces, power management and sensor functions allow for cost-effective scaling of manufacturing test?

If you are interested in presenting your own experiences in solving these challenges then follow the Call for Papers link at: http://www.semiconeuropa.org/node/3356 and submit an abstract before April 29.  Otherwise, make a note in your diary and plan to attend the conference on October 25 – 26.

More information is available here:  http://www.semiconeuropa.org/sites/semiconeuropa.org/files/data15/docs/SCEU16_Adv%20Packaging_Call%20for%20Paper-final%20%281%29.pdf

How do you measure the effectiveness of your test cell?

Overall Equipment Effectiveness (OEE) aligns the activities of production test to critical measures for helping customers run their test floors like finely-tuned machines.  These measures are linked to delivering quality devices efficiently and cost effectively.

Through the use of OEE, customers can identify how to produce more good parts per hour, how to increase test cell availability for testing more parts, while eliminating test cell waste as measured in time, scrap, rework, and unscheduled test cell repairs and or maintenance.  Even when semiconductor demand is down, test system availability means the ability to respond immediately to unexpected increases in test production schedules.  With simple OEE measures and calculations, OEE can be generated for each test cell and each product type being tested.  Another benefit of OEE is that it makes it easy for everyone to see the effect of each action leading to an improvement and to justify this action with evidence.

Interested to learn more?  Then download the complete paper and learn how you can use OEE to maximize the performance of your test cell.

Download the complete OEE paper

Smart Things Need Flexible Test

The Internet of Things (IoT) is expected to drive demand for tens of billions of devices by 2020 and these IoT end nodes or “Smart Things” will integrate multiple functions, including sensors, microcontrollers and RF interfaces, each presenting unique test challenges which are continuously evolving. Peter Cockburn, Senior Product Manager Test Cell Innovation at Xcerra, highlighted in his presentation at the nmi R&D Workshop the technology trends for these Smart Things and described two case studies where test solutions have been developed for two examples of IoT “Smart Things”: RF SOCs and MEMS sensors, where flexibility and low cost of test are key requirements.

Download the full article here

IPC Standards for Electronics Manufacturing

IPC standards, the results of industry consensus and collaboration, are respected throughout the whole world. Using IPC standards ensures manufacturer, customers and suppliers use the same terminology. The standards for Printed Circuit Boards are categorized into chapters about

  • Acceptance
  • Fabrications
  • Flexible Circuits
  • General Definitions
  • High Density Interconnect
  • High Speed / High Frequency
  • Materials – Foils
  • Materials – Laminate
  • Materials – Reinforcements

IPC  provides a graphical overview about all these.

Download the IPC poster here

Xcerra’s PCBA Test Fixtures Group additionally provides a guideline for Text Fixture Specification. Read more here: http://ect-fsg.com/fixture-specification-guideline