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FAQ
- What is “piezoresistive”?
Piezoresistive literally means electromechanical. Pressure exerted on the sensor causes a mechanical deflection of the silicon diaphragm. In turn, this mechanical deflection (essentially the deformation of the crystal lattice structure of silicon) causes a change to the electrical properties or output of the implanted resistors.
- What are “pressure sensor components”?
Pressure sensor components are die or chips and simple assemblies of the same. Transmitter and transducers are fully packaged and conditioned/calibrated sensors.
- What are the various pressure types?
Gage: pressure relative to atmospheric or ambient pressure
Absolute: pressure relative to a perfect vacuum or sealed reference--zero pressure
Differential: pressure exerted on both side of the diaphragm—the difference between two pressures
Vacuum: negative pressure or pressure applied in reverse
- What is “media”?
Media is the environment to which the sensor is exposed. Generally, this can be liquid, gas or air.
- What is a “waffle pack”?
A waffle pack is a container that houses die that have been singulated from wafers.
- What is “sensitivity”?
This is the electrical output of the sensor to a specified, applied pressure. We state this in terms of microvolts per volt per psi.
- What is “resistance” or “impedance”?
This is the amount of electrical resistance a circuit is experiencing.
- What is “bridge configuration”?
This pertains to a “wheatstone bridge” and determines the number of connection points or pads. Bridge configurations are open (6 contacts), half closed (5 contacts) or closed (4 contacts). The performance of each is the same.
- What is a “constraint”?
Silicon wafers typically have a glass or pyrex support or constraint. Constraints come in gage or absolute configurations.
- What is “offset”?
Offset is the electrical output at zero pressure.
- What is “TCR”?
TCR or temperature coefficient–resistance is a factor used for temperature compensation. It relates to the resistance impact to the output due to temperature.
- What is “TCS”?
TCS or temperature coefficient–sensitivity is a factor used for temperature compensation. It relates to the sensitivity impact to the output due to temperature.
- What is “TCZ”?
TCZ or temperature coefficient–zero is a factor used for temperature compensation. It relates to the impact to the output at zero pressure due to temperature.
- What is “linearity”?
This relates to the output of the die at various pressures throughout the pressure range or span. In general, the output is compared to a straight line. The maximum deviation from the line is expressed as a percent of full-scale output (FSO).
- What is “hysteresis”?
This relates to the output of the die at increasing and then deceasing pressures (or temperature cycles) throughout the pressure range or span. In general, the output is compared against itself for consistency. Hysteresis is expressed as a percent of full-scale output (FSO).
- What is “proof pressure”?
This is an elevated pressure at which the die still functions.
- What is “burst pressure”?
This is the pressure just before the die bursts or ruptures.
- What is a “bond pad”?
The bond pad is an electrical contact point where the die can be connected to a substrate.
- What is “Sentium®”?
This is a proprietary set of processes developed by Merit to achieve a wider operating temperature range, especially at higher temperatures.
- How should the die be handled?
Very carefully. Die are susceptible to static and stress and should be handled with a vacuum pick-up tool to avoid damaging the die.
- How should the die be shipped?
Die should be shipped in an electrostatically discharged (ESD) container (clamshell with wafer on tape, waffle pack, etc.) and protected against shock and vibration.
- How should I mount and connect to the die?
Die should be mounted with a low-hardness silicone glue. Die should be connected to a substrate using an ultrasonic gold or aluminum wire.
- What should I consider when packaging the die?
Packaging-related impacts to the die can be significant. Selected impacts to consider are as follows: package materials (metal, plastic, other), filling (oil or air) and media (gas, liquid and air). Care should be exercised in these and other areas and professionals should be consulted, as needed.
- What is the “topside” of the die?
The topside is the electrical side of the die.
- What is the “backside” of the die?
The backside is the cavity side of the die.
- What is an “SMD”?
An SMD is a “surface-mountable device”—a device that can easily be handled and connected to a substrate. The die down, wire bonding, cap attach and gelling processes have been performed.
- What is “gel”?
Gel is a protective coating to isolate the die from the media. It is made of silicone—not to be confused with silicon. It cannot protect the die against all media.
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