Development of “smart devices” and the impact they have on test socket design

Do you remember when telephones had dials and cords?  When consumer-based World Wide Web access was paid for by the minute and ran through baud modems and telephone landlines?  When it would be laughable to think that we could send not only animals and people but cars into orbit?  With the rapid advance in technology and the way it permeates our lives, it’s safe to say it’s only a matter of time when the test challenges we face today will fall wayside to those of pioneering products and commonplace luxuries of tomorrow.  The trend appears to be “smart everything!”  Smart cars, smartphones, smart accessories, smart medicine, smart price tags, smart appliances… smart HOMES! Well, we’re still working on “smart A.I.” but it’s in the works. All of this “smart” technology is based on the integration of core MCMs, SOCs, hybrid modules, and their interactions with one another at the hardware and software level.  These advanced devices not only require programming but also custom PCB module layouts to fit the ergonomics and function of the final product.

The Problem:

Off-the-shelf test socket design for standard IC geometries aren’t adequately suited to meet the various electrical, mechanical, or thermal requirements of custom multi-chip module (MCM) devices.  The development of complex small scale MCM devices is no longer limited to just the silicon architectures residing in a single lead frame but extends to many components across board-level sub-assemblies.  These custom sub-assemblies each have unique form factors and are typically designed to function together to ensure a reliable final product.

Tighter pitches at higher performance for custom embedded system-on-chip devices linked with PCB sub-assemblies and hybrid modules challenge test socket manufacturers to be creative and adaptive in engineering test socket solutions.  Programming and embedded unit testing is expensive but required in many cases due to the scope and purpose of the subsequent sub-assembly module or final product.  Embedded test sockets for programming a single device on a prototype board may require custom mounting footprints to interface with an existing programming/evaluation board layout, which in many cases requires a custom test socket.

“The system in package (SIP) market is likely to witness high growth in the coming years due to the increasing need for advanced architecture in electronic products and the growing market … is expected to grow from USD 5.44 Billion in 2016 to USD 9.07 Billion by 2023, at a CAGR of 9.4% between 2017 and 2023.” – | Nov. 2017

Technology is becoming smaller and more customized.

The fundamental purpose of test sockets has stayed relatively unchanged over the years.  However, advanced proprietary embedded technologies for use on multi-chip-modules with unique form factors continue to push the limits of what can be achieved across all industries and applications.  Although “standard” test sockets for production and burn-in are still available for select IC packages, the demand for smaller and more powerful chipsets is growing.  The shrinking size of MEMs, Optoelectronics, and embedded SOC’s extend the importance of integrated MCM’s on custom PCB modules.  This impacts the layout and performance requirements of the proprietary module sub-assembly leading to the need for custom-engineered test socket solutions.  Let’s face it, test sockets have evolved with the growth of technology and need to address more than standard array single die IC packages while meeting acceptable pricing, quality production, and reasonable turnaround times.  After all, customers need to maintain their schedule, maximize yield, and at a reasonable cost of ownership.

Consider This:

The old saying goes: “The bigger they are, the harder they fall.”  Similarly, the more margin for error introduced into any given complex architecture the more opportunity there is to create a problem down the road.  The more complicated a design becomes, the more important it is to ensure that the reliability of each component is as close to 100% as possible.  One of the most worrisome bottlenecks in creating complex MCM’s with embedded SOC parts is ensuring the logic in your programmed device(s) is ready for flowing onto the MCM module board assembly so that it can move to the next stage.  Investing in a reliable and custom-tailored test socket for your module helps you test and program with confidence so that potential problems down the road can be avoided before they even arise.

“According to well-known studies, fixing an error early is much cheaper than fixing that same error late in the integration test phase or in the system test phase.” – | Nov. 2011

Integrated custom test sockets to the rescue!

At this point, it’s best to focus on what you do best – develop your product with functionality and footprint in mind. Rather than trying to design around an existing test socket, or retrofit a socket to fit your DUT,  find a highly qualified test socket and test fixture solutions provider.  Your provider needs a solid understanding of your test parameters including electrical, physical/mechanical, and thermal requirements.  Remember that custom test sockets in lower quantities may be more expensive than off the shelf sockets – but consider the overall cost of ownership when it comes to reliability of results and longevity of the product.

MCMs mounted to ridged and flex PCB module devices are becoming more prevalent and customized to meet specific form factors and functionality determined by the final application.  Modules and units continue to demand more power, higher speeds, and tighter tolerances in architecture.  Make sure your test socket is designed with your details in mind.  Here are five capabilities you may consider when qualifying a test socket provider:

  1. Mounting footprints.  Namely, internal vs. manufacturer standard and custom mounting footprints for surface mount (soldered) or compression mount (spring pin/elastomeric) contact sets.  Contact sets are often identified by contact resistance, electrical performance, and type of point of contact – balled, padded, castellated PCB, coaxial, Kelvin, and even micro connectors.  If the test socket needs to mount to an existing eval or programming board, make sure your supplier can accommodate your working area.
  2. Location and type of test points on the DUT.  Test sockets requiring fine-pitch arrays (sub 400micron), interstitial arrays, and custom pin drilled locations should be acceptable by your provider.  Test sockets and lids should also be able to contact DUT modules with test points at different Z-heights and contact one or more surfaces of the device such as the top, bottom, and sides simultaneously.  Precise drilling and manufacturing also allow for contact to plated, castellated pads on a PCB module.
  3. Awareness of additional components while maintaining access to MCMs and SOCs on the module.  Test sockets and lids can include relief cut-outs to accommodate module devices with SMT components such as MOSFETs, diodes, connectors, and more.  Sockets and lids can also include openings at specific areas for physical and optical access to the DUT module.
  4. The longevity of modules using micro connectors.  Some module devices include a low profile high-performance micro connector which have low lifespans (50 or less!).  Connector Saver test blocks reduce wear on these fragile snap connectors.  They use fine pitch pogo pins to safely contact each signal on the mating connector or can contact a flex PCB pad directly.  Precision alignment of the DUT to the socket is crucial so be sure that your module includes non plated alignment holes.
  5. Thermal management.  Test socket and lids can incorporate temperature control and measurement methods at the embedded system on chip and MCM module-level all the way up to the complete PCB sub-assembly level.  Incorporated thermocouples, active and passive heating, and cooling blocks, and airflow cavities may be required to ensure the proper performance of your device under thermal stress.

From a one-person crowdfunded upstart to a small or medium-sized development team, it is easier now than ever to build a unique product that will be the next big thing in our lives, impacting how we interact with the world and each other.  As innovative technology grows, so should your test solutions provider.  Maximize your cost of ownership by investing not only in your embedded software and hardware, multi-chip module, and PCB module devices but also in high-quality test sockets and test fixtures that meet all physical and performance requirements demanded by your DUT module.