September Tech Focus: Maximizing connections

Serving the role of connecting a device and its tester, test sockets—also known as package probes—play a crucial interconnect role in integrated circuits (IC), and therefore the greater field of semiconductor testing.

Depending on the purpose of the test, IC sockets are categorized into two either 1) test sockets for measuring electrical characteristics, or 2) burn-in sockets for testing reliability. Both types are generally referred to as IC sockets, although their required performance varies depending on the difference in use. IC sockets’ applications include the aforementioned burn-in test, failure analysis, engineering test, production test, and more. Most IC sockets are compression-mounted and can be designed to fit an existing printed circuit board footprint.

Designs of test and burn-in sockets are robust, cutting edge, and are often produced in small quantities but at very high costs. They are typically tested in excess of 100,000 touchdowns before socket rebuild.

Market outlook

According to a report released in June 2019 by Mordor Intelligence, a few of the key factors impacting the IC test socket market include1:

  • The increasing popularity of enterprise technologies like Big Data, and cloud-based services and the dependency on servers and CPUs with high computing power has been increasing significantly over the past few years, further leading to the growth of this market. Companies like Intel and AMD are using new processors. These new processor platforms require socket designs to meet the design requirements and offer higher performance and better system scaling.
  • With the advent of the Internet of Things, coupled with an increasing focus on automation in the automotive and manufacturing industries, the IC socket market is expected to grow during the forecast period.
  • The trend of miniaturization has been a challenge for the IC sockets market, as they tend to occupy additional space and add an extra electrical signal path to the IC device.

That same report forecasts that the IC socket market is expected to see a CAGR of 9.11% between 2019 to 2024, adding that their consumption has witnessed rapid growth over recent years in correlation to the increasing demand for performance and efficiency.

Some of the leading companies in the test socket market include TE Connectivity, Ironwood Electronics, Smiths Interconnect, Mill/Max Manufacturing,

In April of this year, VLSIresearch released a report that detailed 2018’s top five suppliers of test and burn-in sockets in the semiconductor industry, by revenue.2 Those five, in descending order, were Yamaichi Electronics, Cohu, Enplas Corp., ISC, and LEENO. The report noted those five companies accounted for 42% of the total test and burn-in socket market in 2018, up from 39% in 2017. Yamaichi had 2018 sales of $124 million, closely followed by Cohu, which climbed to second place following its acquisition of Xcerra.

VLSIresearch’s report noted that after the exceptional growth in the test and burn-in socket market in 2017, 2018 was a year of digestion, with market growth of only 2.3%.

 “The rollout of 5G over the next few years is going to present multiple technical and cost challenges for suppliers of test and burn-in sockets,” commented VLSIresearch Europe managing director John West. “This may favor the larger suppliers with the resources to overcome these problems, but I wouldn’t rule out the possibility of some smaller companies playing a major role”.

Here's a look at a few recent product introductions in test sockets.

75GHz BGA Socket for NXP's BGA388 Ironwood Electronics

Ironwood Electronics has introduced a new BGA socket design using high performance elastomer capable of 75GHz, very low inductance, and wide temperature applications. The GT-BGA-2105 socket is designed for 15x15 mm package size and operates at bandwidths up to 75GHz with less than 1dB of insertion loss. The socket is designed to dissipate 5 watts using a heat sink compression screw and an axial flow fan. The contact resistance is typically 30 milliohms per pin. The socket is mounted on the target PCB with no soldering and uses very small real estate, allowing capacitors/resistors to be placed close by. Other passive components can be placed on the back side of a PCB by creating custom cutouts in the stiffener plate. The socket is constructed with swivel lid which incorporates a quick insertion method so that ICs can be changed out quickly. The GT-BGA-2105 socket’s temperature range is -55 C to +160 C. It works with ICs such as 388 BGA, 15x15mm with 35x35 array, and mixed pitch (min 0.56mm).
Ironwood Electronics

Extra large array socket series Te Connectivity

In the summer of 2018, TE Connectivity introduced its extra-large array (XLA) socket technology, which it said provides more reliable performance with 78% better warpage control than traditional molded socket technologies. The XLA socket technology allows TE to design enhanced sockets to support high data speeds in next-generation data centers. The utilization of PCB substrates versus other plastic materials results in minimal warpage and enables TE to design the industry’s largest one-piece socket, with sizes up to 110mm x 110mm and a 10,000+ position count capability. Because of such large capacity, these sockets are capable of extremely fast data rates up to 56G bps. According to TE Connectivity, XLA socket technology also offers 33% improved true position on the solder ball and contact, low coefficient of thermal expansion mismatch to motherboard, and mitigates SMT risks during customer application. Two versions are available: the hybrid land grid array/ball grid array (LGA/BGA), and the dual compression LGA/BGA.
TE Connectivity

0.65mm pitch coaxial socket Smiths

In 2018, Smiths Interconnect releaser its new DaVinci 45G 0.65mm pitch coaxial socket, an extension to the DaVinci 45G portfolio, which provides high reliability and superior durability in high speed testing. The socket provides a higher speed, compact solution that supports tighter 0.65mm pitch requirements for testing GPUs/CPUs. The proprietary design ensures long lasting coaxial impedance accuracy because of the signal probe design and patented IM-coated body structure to achieve high reliability and superior durability in high-speed testing. The new DaVinci 45G 0.65mm pitch socket offers a number of benefits: high speed, at >45 GHz/32 Gbps; >3A current carrying capacity; excellent heat transfer property; rigorous design validation, RF measurements, custom electrical, and mechanical simulations at Smiths Interconnect’s lab and engineering facilities.
Smiths Interconnect

References
 1. Mordor Intelligence, “The IC Socket Market: Global Growth, Trends, and Forecast (2019-2024),” June 2019.
 2. VLSIresearch, “Top 5 Test & Burn-In Socket Suppliers for 2018,” April 2019.
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