For more than half a century, the semiconductor industry has been governed by a commonly known principle described as Moore’s Law. This “law” predicts that through technological advancement a doubling of the number of transistors per integrated circuit will occur within a given geometric area on regular 18 month intervals. The realization of this doubling effect over time has resulted in an ever-widening range of semiconductor (IC) devices exhibiting increases in functionality and processing speed, combined with an increased demand for power and effective thermal management. This doubling effect has also driven a matching rapid evolution in IC package types (microprocessors, LEDs, memory packages, etc.) and I/O interface configurations.

Figure 1 – Six stages of IC product life cycle.
LEDs are in high demand lately due to their established position in backlighting of portable devices and their increasing use in mainstream backlighting for large-sized LCDs. LEDs gained their market position due to features like energy-efficiency, environmental friendliness, long life, and low maintenance. LED driver circuits play a major role in this area, depending on the application, as they have to supply constant current with minimal fluctuations as well as low power consumption. LED controllers/drivers come in standard IC packaging formats, and these ICs have to be tested for functionality before being incorporated into the final production systems.

altThe typical life of an IC starts with the concept/prototype phase, moves to the design validation phase, leaps into the application development phase, soars into the marketing/sales phase, rides into the production phase and ends with the upgrade/replacement phase (Figure 1). During these phases innovative interconnects have kept pace with the rapid evolution in semiconductor technology. IC sockets have been developed for a complete range of performance requirements and I/O configurations for each of those phases. This article will describe the form, fit and function requirements of IC sockets in each of those phases.

Concept/Prototype Phase

The important step in this phase is to verify whether the prototype functions as per the design intent. Since there can be revisions to the IC, an IC socket in the development board helps to avoid the routine of soldering and de-soldering devices.

The IC socket plays a major role in determining whether the device meets design intent or not. Because of this, the IC socket has to be carefully selected. The number one factor is bandwidth. Because the IC has to perform certain functions at specific speed, the signal loss has to be minimal.

Since additional socket interface introduces losses in the signal loop, either the socket has to have sufficient bandwidth to pass signals without insertion/return losses, or the socket specifics have to be de-embedded in the functional verification. Since it is very complex to de-embed specific parameters, a safer solution is to find a socket with higher bandwidth.

Next to bandwidth, DC series resistance plays an important role. Socket technology that can provide low and consistent contact resistance is preferable to avoid false failures.