Global Standards for the Microelectronics Industry
Dictionary U
U
See "upper byte".
References:UART
See "universal asynchronous receiver transmitter".
References:UB
See "upper-byte enable".
References:UJT
See "unijunction transistor".
References:ultraviolet-erasable programmable read-only memory (UV-EPROM)
Synonym for "erasable programmable read-only memory (EPROM)".
References:JESD100-B, 12/99
uncased device
A device with some portion of the die exposed.
NOTE Usually the chip has bonding pads, bumps, etc. that may be bonded to pads or lands on a lead-frame, tape, substrate, or printed wiring board.
References:JESD30D, 7/06
uncommitted logic array
Synonym for "gate array integrated circuit".
References:uncorrectable bit-error rate (UBER)
A metric for data corruption rate equal to the number of data errors per bit read after applying any specified error-correction method. References: JESD22-A117B, 3/09under-bump metal (UBM)
The metal layers located between the solder bump or column and the die. References: JEP156, 3/09under-bump metallization (UBM)
A patterned, thin-film stack of material that provides 1) an electrical connection from the silicon die to a solder bump; 2) a barrier function to limit unwanted diffusion from the bump to the silicon die; and 3) a mechanical interconnection of the solder bump to the die through adhesion to the die passivation and attachment to a solder bump pad. References: JEP154, 1/08under-bump metallurgy (UBM)
The metal layers located between the solder bump and the die. References: JESD22-B109A, 1/09undercut
The reduction of the cross section of a material caused by etching action spreading beneath the edge of the photoresist or other masking films.
References:JESD99B, 5/07
underfill
The adhesive material applied between the solder bump side of the flip chip die and the substrate.
References:JESD22-B109, 6/02
underplate
Plated layers between the base metal and the outer surface finish.
References:JESD201, 3/06
undetectable fault
A functional fault for which no test pattern can be created that will cause the effects of the fault to be observable at an externally accessible node.
References:JESD12-5, 8/88
undetected fault
A functional fault that causes effects that are not observed at an externally accessible node when the circuit is exercised by the existing test pattern.
References:JESD12-5, 8/88
unidirectional ABD
A two-terminal ABD with a voltage-current avalanche breakdown characteristic in one direction and either a forward or a blocking characteristic in the otherNOTE Large transient currents will be clamped for positive cathode-to-anode voltages when driven into the avalanche breakdown region with one or more p-n junctions placed in series or parallel with each junction connected in the same direction. Large transient currents may also be clamped for negative cathode-to-anode voltages at significantly lower voltages with the typical forward-conducting characteristics of a single p-n junction (or of multiple p-n junctions connected in the same direction). The most common type of unidirectional ABD has a forward-conducting characteristic.
Unidirectional-conducting ABD Unidirectional-blocking ABD References: JESD77C, 10/09
JESD210, 12/07
unidirectional thyristor surge protective device
A thyristor surge protective device (TSPD) that can switch in only one quadrant.
NOTE The two types are forward-conducting TSPDs and reverse-blocking TSPDs.
References:JESD77-B, 2/00