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Wafer
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Wafer Level Burn In
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(WLBI) -
Wafer Level Burn In is a manufacturing technique where a particular product is burned in as full wafers to take advantage of massive parallelism and higher temperature acceleration factors.
Source: NPTest
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Wafer Map
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A plot of the viable dice on a wafer showing pass/fail information, parameter variation, or some other characteristic.
Source: ATE World
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Wafer Probing
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The process of testing individual integrated circuits while they still form part of a wafer. An automated tester places probes on the device's pads, applies power to the power pads, injects a series of signals into the input pads, and monitors the corresponding signals returned from the output pads.
Source: Maxfield & Montrose Interactive Inc.
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Wafer probe or test is the first time that chips are tested to see if they function as they were designed to do. There are three basic tools used as a set to perform this operation.
First, the wafer prober is a material handling system that takes wafers from their carriers, loads them to to a flat chuck, aligns and positions them precisely under a set of fine contacts on a probe card. Mostly, this test is performed at room temperature, but the prober is increasingly being required to also heat or cool the wafer during test.
Secondly, each input-output or power pad on the die must be contacted by a fine electrical probe. This is done by a probe card, whose job is to translate the small individual die pad features into connections to the tester.
Thirdly, the functional tester or automatic test equipment (ATE) is capable of functionally exercising all of the chip's designed features under software control. Any failure to meet the published specification is identified by the tester and the device is cataloged as a reject. The tester/probe card combination may be able to contact and test more than one die at a time on the wafer. This parallel test capability enhances productivity at wafer probe.
Source: Infrastructure
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Walking Sequence
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A sequence of test patterns at which the test vectors contain only one ‘1’ between all zeros (walking ‘1’) or vice versa (walking ‘0’). This vector shifts through the scan path such that the logical value, either the ‘1’ or the ‘0’, is applied to all nets, one at a time.
Source: Hebrew University of Jerusalem "DFT & JTAG" Course
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Watch-Dog (Watchdog)Timer
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A hardware or software count-down timer that must be repeatedly reset at regular intervals by an operating program to prevent time-out. If the timer is not reset in time (meaning the operating program has stalled or has failed in some way), the timer times-out and alerts the system and/or operator of the failure.
Source: Measurement Computing
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Wave Soldering
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A process used to solder circuit boards populated with through-hole components. A wave generating mechanism maintains a wave of hot, liquid solder traveling back and forth across the surface of a tank. The populated circuit boards are passed over the wave soldering machine on a conveyer belt. The velocity of the conveyer belt is carefully controlled and synchronized such that the solder wave brushes across the bottom of the board only once.
Source: Maxfield & Montrose Interactive Inc.
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Waveform
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A presentation or display of the instantaneous amplitude of a signal as a function of time, as on an oscilloscope or oscillograph. In the time domain.
Source: Vibration and Shock
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The waveform is the shape of a time domain signal as seen on an oscilloscope screen. It is a visual representation or graph of the instantaneous value of the signal plotted against time. Inspection of the waveform can sometimes reveal information about the signal that the spectrum of the signal does not show. For instance a sharp spike or impulse and a randomly varying continuous signal can have spectra that look almost identical, while their waveforms are completely different. In machine vibration, spikes are usually caused by mechanical impacting, while random noise can be caused by the advanced stages of bearing degradation.
Source: Vibration Institute
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Waveform Analyzer
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An oscilloscope-like instrument that displays data as waveforms and contains a comprehensive set of waveform processing functions and operations.
Source: A.T.E. Solutions, Inc.
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Waveform Generation Language
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(WGL) -
( pronounced "wiggle"). WGL is the de-facto standard for ATPG and vector generation. Most pattern development tools support WGL and there are third party tools that specialize in the conversion of WGL to various tester native vector formats.
Source: NPTest
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(WGL) -
An older test program language that is
slowly being replaced by STIL.
Source: Mentor Graphics
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Waveform Generator / Fast Measurement Unit
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(WGFMU) -
A measurement module that can generate arbitrary waveforms (with 10 ns programmable resolution) and measure both current and voltage extremely fast (5 ns sampling rates).
Source: The Paramatric Measurement Handbook
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Waveguide
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A transparent path bounded by non-transparent, reflective areas, which is fabricated directly onto the surface of a substrate. Used in the optical interconnection strategy known as guided-wave.
Source: Maxfield & Montrose Interactive Inc.
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Wavelength
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The distance that an electromagnetic wave travels in one complete cycle.
Source: Xilinx
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Wavelength Division Multiplexing
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(WDM) -
A technology that uses optical signals on different wavelengths to increase the capacity of fiber optic networks in order to handle a number of services simultaneously.
Source: HostPulse
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Weapons Replaceable Assembly
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(WRA) -
A generic term that refers to a part of an equipment which is separately installed/replaced in the aircraft.
Source: McDonnal Douglas Aerospace
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Web Based Diagnostics
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Web-based diagnostics is a type of remote diagnostics where interaction with the diagnostic engine is achieved through a web interface.
Source: Testability.com
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Weber (unit)
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(Wb) -
The weber may be defined in terms of Faraday's law, which relates a changing magnetic flux through a loop to the electric field around the loop. A change in flux of one weber per second will induce an electromotive force of one volt.
In SI base units, the dimensions of the weber are kg·m2·s−2·A−1. In derived units, they are volt-seconds (V·s).
The weber is a large unit, equal to 1 T m2 = 108 maxwells.
It is named after the German physicist Wilhelm Eduard Weber (1804 - 1891) and was established by the IEC in 1930 [1]
Source: Wikipedia
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Wedge
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An optical element with its faces inclined toward each other at very small angles, diverting light toward the thicker parts of the element.
Source: JML Optical
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Weibull Distribution
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A statistical distribution that is widely used for matching field data, due to its versatility and the fact that the Weibull probability density function can assume different shapes based on the parameter (beta factor) values.
Source: Testability.com
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Wetting
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Ability of a liquid to flow across a surface as opposed to sticking to itself. Wetting occurs when the attractive surface energy of the pad or lead is greater than the surface energy of the solder, drawing a molecularly thin layer of solder across itself. Heating solder adds to the surface energy in the solder, so the cooler the solder the better the wetting. Good wetting is indicated by a low contact angle between the fillet and the base metal.
Source: OK International
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