Conformity Magazine - July 2008 - (Page 26)

ESD Open Forum Human Body Model Stress Voltage Levels Provided by the ESD Association Q: A: The Industry Council on ESD Target Levels has proposed that OEMs (original equipment manufacturers) reduce their Human Body Model (HBM) minimum passing stress voltages from 2000 V to 1000 V [1]. How does this recommendation affect the existing HBM test standards? The HBM test standards, ESDA STM5.1 or JESD22-A114E, both define how to perform the HBM test, what type of ESD equipment to use, and a method for validating the discharge waveforms. Each standard defines HBM classification levels as a way to compare the electrostatic sensitivity levels between different IC components. Thus, the standards do not set any specific HBM requirements that an IC component must meet. The end customer (OEM) who is purchasing the IC component defines the minimum acceptable HBM voltage level requirements. Q: A: The Industry Council on ESD Target Levels has reported that the customer factory failure rate for IC components that fail at 1000 V do not have any higher customer return rate than components that fail at 2000 V [1]. Does this new HBM data suggest that the existing HBM standard test methods are too restrictive? This is a good question. The existing HBM test methods were first developed in the late 1980s as replacement test method for the MIL-STD 883D, Method 3015.7. When the HBM standard was first developed, the largest IC components tested at that time had at most 64 pins, with one Vcc and Vss pin. Some of the first HBM test simulators were manual two pin testers and all testing was done manually. The same test pin combinations, all signal pins (Inputs, I/O, Control pins) were each stressed to the single power and ground pins. In addition, a new pin combination was introduced that required that each signal pin be stressed to each other signal pin. This test combination was quickly modified when the total number of manual pin stresses became extremely excessive. The signal pin to signal pin stress test was modified to the case where each signal pin was stressed to all other signal pins ganged together and grounded. In today’s semiconductor industry, IC components with more than 512 pins or balls are quite common for both low-cost and 2 Conformity JULy 2008 cost-performance packages [2]. In addition, many of the IC components have a minimum of 4 – 5 independent power or ground pins with as many as 100 power and ground pins or balls. Since the HBM pin combination stress methods have not changed, the total number of HBM stresses for a single test voltage level for this type of device would easily reach 3300 pulses. In contrast, the 64-pin IC component built in early 1990s received approximately 640 pulses. In 1990, the HBM standards required that each signal or I/O pin be stressed 5 times per HBM ESD stress level, instead of existing HBM requirements of 1 stress per polarity and stress level. Even though the existing HBM test method has increased the total number of HBM pulses to a single pin, the HBM Component Level Classification Tables have not changed. All pins in an IC component must pass all pin combinations tests at any given voltage stress level, independent of the number of pins in the package or number of HBM stress pulses. The existing HBM standard classification levels treat a 500pin IC component with 1 or 2 pin failures in the same way as a 64-pin package device with 1 pin failure. The existing test methods describe how to perform an HBM stress, but the test methods are missing an important factor in defining the classification levels. As the number of pins or balls increase in an IC component, the probability that a specific pin combination will have an ESD discharge event is ignored.

Table of Contents Feed for the Digital Edition of Conformity Magazine - July 2008

Conformity Magazine - July 2008 Contents Editor's Note FCC Adopts 6 Million Dollars in DTV Enforcement Orders Commission Enforcement Bureau Adopts V-Chip Consent Decree FDA Seeks 2 Million Dollars from Medical Device Manufacturer FDA Answers Questions About CFLs and UV Radiation EPA Issues Energy Star Specs for TV, Video Boxes Canada Unveils Sweeping Product Safety Legislation How the Evolution of CISPR Standards Continues to Shape the Requirements for Anechoic Chambers ESD Open Forum Reach Compliance for Non-EU Article Manufacturers The iNARTE Informer Preamplifier Considerations for Emission Measurement Systems Effective Shielding in Medical Electronics Applications Product News Focus On...Power Components Buyer's Guide Updated Standards List for the EU's ATEX Directive EOS/ESD Symposium Set for September CPSC Actions in the News Researchers Work to Develop Non-Flammable Batteries Safety Link Launches Redesigned, Enhanced Web Site IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our "You Can't Make This Stuff Up" Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - July 2008

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