SA20Crash Sensor

* Millions On The Road* Proven Reliability

SA20 Crash Sensor

GeneralThe SensoNor SA20 CrashSensor is used by a number ofair-bag system manufacturingcompanies and has madeSensoNor the world’s no. lindependent manufacturer ofelectronic crash sensors. TheSA20 represents SensoNor’s2. generation of crash sensorsand is based on our experiencesince the mid 80ties as a crashsensor supplier.We commit 100% to ourcustomers goals regarding costs Interior Viewand reliability. In practice thismeans that SA20 is produced in afully automated, high volume, element, it will be interfaced to apurpose built production line. range of well proven signalA carefully developed control conditioning interfacing circuits.plan is utilized to safeguard theproduction. An innovative concept of barcode

marking the sensitivity onto theSince the production start SA20 package of each individual sensorhas been installed in millions of makes it easy to automaticallysystems. During these years SA20 calibrate the sensor duringhas proven its exceptionally good system assembly at our customers.reliability. In addition, our worktowards continuous improve- The excitation can be eitherment has paid off in improved voltage or current. By currentyields and improved effectiveness. excitation of a piezoresistiveThese facts in addition to the semiconductor strain gage a welltechnical approach in utilizing known "intrinsic" temperaturewell proven technology makes compensation can be achievedSA20 the first choice in crash since the positive TCR of thesensing. bridge resistor compensate, for

the negative TCS of the piezoApplication resistivity.SA20 is well suited for a range ofsystem realizations. Due to a A diagnostic resistor is coveringflexible production set-up a variety the rim of the elastic element.of pin configurations are possible; Monitoring the electricalRanging from a DIL concept for consistency of this resistor makessensitive direction normal to the it possible at all times to verifyPCB, to a SIL concept meant for the mechanical consistency ofsensitive direction horizontal to the device.the PCB, to special pin bendingmeant for surface mount. Since Conceptthe SA20 includes a simple full SA20 utilizes only a singlebridge piezoresistive sensing (no sandwitch) very small

Photo of Cantilever Chip(50x magnified)

SA20 Crash Sensor

(2.5mm times 0.9mm) single process makes the sensing resistors and it will be extremely linear incrystal silicon element. This insensitive to surface effects like the specified range to +/-50g.element is directly forming a contamination.cantilever beam made possible Transportation Packagingby the combination of anisotropic Function SA20 is shipped in ESD proofetching and diamond saw dicing. When exposed to an acceleration plastic magazines in customized

field the inertia of the seismic mass shape and length according to theOnto the tip of the silicon beam will cause the silicon beam to mechanical pin configuration anda ceramic seismic mass is bend. The piezoresistors located customer specifications.bonded using a slit design. The near the surface of the beam willpiezoresistive bridge consists of feel a high mechanical stress andtwo transversal and two long- they will change their value due toitudinal piezoresistors located in the piezoresistive effect in dopedthe maximum stress region. silicon. The change will be with

opposite sign for the transversalThe sensing element is housed in and the longitudinal resistors,a high reliability low cost welded giving a full bridge output. Due toPPS plastic housing. The inside the full bridge design, zero-pointcompartment is filled with shift as a function of temperature isinstrument grade silicone oil for low. The output signal. is directlycontrolled dynamic damping. As ratiometric to the excitation signal.an integrated part of the housinga thinner plastic area acts as a The silicone oil viscosity is chosendiaphragm to equalize the inside to achieve critical damping at roompressure over the operational temperature.temperature range.

Cross axis sensitivity is low due toReliability is optimized by avoiding the ceramic mass which is symme-mechanical overload stops which trically located as referred to themay cause internal fractures and bending plane.by the moisture preventingsurrounding silicone oil. The output signal will have aIn addition a “ buried”-resistor good linearity even above +/-500g

Electrical Schematic

Magazine Package

SA20 Crash Sensor Specifications

SensoNor asa P.O.Box 196. N-3192 Horten Norway, Tel: +47 33 03 50 00, Fax: +47 33 03 51 05E-mail sensonor@sensonor.no

Specifications may be subject to alteration without prior notice.