Kulicke & Soffa looks at how the company has changed and is moving beyond its leading packaging and assembly technology. With decreasing linewidths approaching, they are ready to tackle interconnect package testing.

Despite recent incremental improvements, the package test industry believes that "spring-pin" testing technology will, at some point, reach its performance and reliability limitations. Continual microelectronic development and miniaturisation of package testing demands technological alternatives that must deviate from traditional methods. Kullicke and Soffa have long being a leader within the test market. With a new photolithographic process based technology they aim to become a packaging leader at smaller dimensions. This article looks at some of the future plans for one of the industry's oldest companies.

The market trend towards smaller and more powerful electronic devices keeps driving the demand for more compact electronic packages, with increased functionality. At the same time, the technological requirements for IC packaging are moving at a rate faster than many semiconductor companies can address.

With over 50 years in packaging assembly technology, Kulicke & Soffa have not only kept pace with current semiconductor demands, but is introducing new technologies to keep up with the changing industry. While well known in the back-end assembly semiconductor sector for its assembly equipment, K&S is developing inroads into the IC package test market.

"Our ability to provide both current and future state-of-the-art test contacting technologies stems from our knowledge of the entire "back-end" semiconductor assembly market," explains Jack Belani, K&S Vice President Marketing and Business Units. "Our knowledge and experience gives us a better understanding of the technological requirements needed to address the ever-changing IC market."

Precision photolithography allows highly uniform contact geometries with repeatability of 3-4 µm.

K&S has developed technologies in response to the industry's most critical package test requirements:

* Smaller packages with higher densities and finer pitches (i.e. DSP in CSP);
* IC devices with higher speeds and bandwidth (RF/wireless, network processing, DDRII memory, etc.);
* Thermal management control (IC packages dissipating 25 - 100 W with requirements for liquid-cooling heat sinking, TCUs, etc.).

To provide solutions to these technological issues without compromising performance parameters, K&S has developed new spring-pin technologies that address high-speed applications of 6 - 12GHz, with corresponding lower inductance (nH specs) and CRES (contact resistance ~ mOhm specs) ratings. The company has also developed enhanced technology that operates with lighter contact forces to support higher pin count packages at pitches as tight as 0.4 mm. K&S' three-in-one lid designs and TCU units also offer real design flexibility in thermal management for today's advanced packaging applications.

Design professionals at K&S IC Package Test have developed test components for the industry's most complex and sophisticated IC packages. The company's wide selection of materials, along with a full complement of spring-loaded, scalable contact pins, enable socket designs for BGA/CSP type ultra-fine pitch devices with pin counts of 3000 and more.

"We've developed the most advanced, high-performance test sockets to address all the critical points along the IC testing map," notes Andrei Berar, K&S Vice President of Package Test Business Units. "K&S has all the credentials of a world-class IC package test manufacturer including experience, design expertise and innovative test capabilities. We also have resources to provide worldwide service and manufacturing support."

By taking the lead in developing many of the most advanced, high performance test sockets ( including those for newer LGA and QFN package types ( K&S is establishing itself as a world leader in IC Package Test.

Customisation to standardisation

In a market where customers sometimes must choose from among 140 different pin designs to create a socket, K&S is also leading the way to change the market assumption that every test socket has to be 'custom-built'. The company is currently spearheading design simplification and spring-pin/frame standardisation to simplify socket ordering and to give customers the most optimised designs within minimum lead times.

Through its long-term experience in back-end semiconductor assembly as well as the socket market, K&S has the knowledge to create a standard family of sockets that minimises the number of designs for faster turnaround, greater unit predictability and faster ramp-up. The company foresees that the number of pins can be streamlined to around 15 key designs that will cover the entire spectrum of IC packages. Standardisation will enable customers to order units quickly and design boards faster.

"Based on over a decade of experience in designing sockets and a clear understanding of market trends for package designs, K&S has established a family of products that provide the long needed standardisation in an industry sector notorious for proliferating variations," explains Berar.

Berar also notes that standardisation will provide immediate cost-of-ownership benefits related to:
* Faster design turnaround
* Shorter time to deliver footprints through online availability of standard designs;
* Faster product delivery times due to a reduced, smaller inventory of common parts required at the factory;
* Reduced overall customer inventory levels due to commonality of designs for different functions.

K&S also anticipates that standardisation will enable the global regional sourcing of "like" products for global Integrated Device Manufacturers (IDMs) at vastly reduced delivery lead times and cost.

"IDMs will be able to place a volume order at one source to address the needs of different locations for better pricing," notes Belani. "However, manufacturers must have the global resources and capabilities to efficiently supply the same product at the same cost for different customer locations."

With manufacturing and support resources and processes already located strategically throughout the world (K&S currently has technology and manufacturing centres throughout the United States, Europe and Asia for test products alone!), K&S has the foundation to provide global sourcing of standardised IC sockets. The company also has service and repair centres around the world to provide faster customer service.

"K&S has already established a global capability to produce "like" products anywhere in the world according to "copy exact" processes," says Belani "With key international support, service and sales locations, K&S can provide true global regional support from an extensive network of customer service representatives and application engineers. K&S personnel are located in key regions to quickly and efficiently service our customers on a local basis."

Next-Generation Test Technology

As spring-pin testing technology matures and reaches its performance and reliability limitations, K&S is breaking away from traditional methods by developing an alternate technology that offers performance unmatched by current IC test technology.

"Our latest innovation is a revolutionary, photolithographic package test technology that serves as an alternative to traditional spring-pin contactor methods for test sockets," states Berar. "Rapid package test microelectronic developments and imperative miniaturisation demands technological alternatives that break from traditional methodologies."

As a single plane of contacts with no moving parts, the Quatrix processor-based technology offers highly consistent dimensional placement tolerances, in conjunction with excellent electrical performances, to meet the most aggressive roadmaps for package test such as LGA, QFN and MLF packages.

Born of a need for a simple and low-profile interconnect solution with a reduced contact path length, photolithographic interconnect technology offers many significant electrical and mechanical advantages over existing methods and allows for a wide range of applications. In addition, the design and manufacturing flexibility using Quatrix technology offers greater potential for providing modular solutions towards a more standardized product offering.

Advanced photolithography techniques provide for the creation of very precise, flexible contact geometries with repeatability of 3 - 4 µm. Shorter paths and more positive contacts than spring pins contribute to an average 20% reduction in resistance. Standard deviation across an array of contacts is on the order of only 3 µm, approximately 3x less than spring pin methods. Accurate positioning tolerance results in very stable and uniform performance for increased reliability and yields.

"As a new photolithography process versus a traditional spring pin machining method, Quatrix provides highly accurate placement from lot to lot, with deviation in the microns instead of mils across an array of contacts," explains Berar. "Its process-based consistency over standard spring pins offers significant reduction in ownership costs, and has direct impact on increasing first path yields."

With lower touchdown forces between the contacts and the package, Quatrix test sockets also eliminate the problems associated with the high combined forces encountered for chips with high-density I/O.

K&S anticipates that Quatrix will take the industry to the next level of testing by eliminating the performance and reliability limitations of spring-pin interconnects. "Quatrix is not just a cutting- edge technology, but a leap frog jump in comparison to existing spring pins," Berar explains.
"This advancement in test sockets provides a new enabling technology with plenty of room for growth in providing new test solutions for emerging packaging types for many years to come."


Expansion of E-Commerce
In addition to technological growth, K&S foresees that e-commerce will also play a greater role in simplifying the design, selection and order process for spring pins, and virtually any K&S product. In addition to ordering and tracking shipments of test sockets on a 24/7 basis, customers will be able to collaborate on designs online and retrieve important documentation. With online access to a footprint design, an engineer can initiate the design process and start loading the board before a socket is even received.

"Using the K&S Connect online business tool, customers can research our products and services, check real-time price and availability, submit orders electronically and track them as well," states Berar. "E-commerce not only simplifies the order process, but reduces order cycle time because time and location are no longer a barrier."

Using the eCollaboration functionality of the K&S e-commerce tool, customers can even ask technical questions, send alerts and provide product requirements for immediate evaluation.

E-commerce, along with product standardization, globalization and advancement, is changing the way manufacturers must do business with customers on a global basis. K&S' customers will benefit from the company's continued investment in these new technologies.

Low profile contacts provide path lengths that are significantly shorter than those of contact pin methods.

Photolithographic production allows for a wide variety of contact forms and design flexibility.

Quatrix' contact resistance stabilizes at a minimum value at a relatively low level of deflection.