MPXM2102AS datasheet(26/670 Pages) MOTOROLA

26 / 670 page

1–20

Motorola Sensor Device Data

www.motorola.com/semiconductors

“C” is intended to swell polymeric materials. Contaminants in

actual gasoline can result in corrosion or material degradation,

so chloride ions or formic acid with distilled water are added

to create an aggressive fuel media. Gasoline can decompose

by a process called auto–oxidation that will form aggressive

substances that can dissolve polymers or corrode metal. Copper

is added as a trace metal to accelerate the formation of free

radicals from the hydroperoxides. Table 2 details the various

gasoline/methanol mixtures with additives recommended by

the task force from Chrysler, Ford, and General Motors.

Table 2. Fuel Testing Methods

Elastomer

Polymer

Metal

Alcohol/Fuel Blends

CMO

CM15

CM30

CM50

CM85

Aggressive Fuel, Add

Chloride ion

Distilled water

Formic Acid

Chloride ion

Sodium Chloride

Formic Acid

Auto Oxidized Fuels, Add

t–Butyl Hydroperoxide

Cu+

Recommended gasoline/methanol mixtures for material testing. The recommended testing for metals should include immersion in the liquid as

well as exposure to the vapor. The coding for the alcohol/fuel blends, CMxx is: C for Fuel C; M for methanol; and xx indicating the percentage of

methanol in the mixture.

The

general

question

for

the

appliance

industry

compatibility issues is not whether the media will contain

ions (as it most assuredly will) but at what concentration.

Tap water with no alkali additives contains ions capable of

contributing to a corrosive reaction [14]. A typical

application of a pressure sensor in the appliance industry is

sensing the water level in a washing machine. The primary

ingredients of detergent used in a washing machine are:

surfactants, builders, whitening agents and enzymes [15].

The surfactants dissolve dirt and emulsify oil, grease and

dirt. They can be anionic or cationic. Cationic surfactants

are present in detergent–softener combinations. Builders

or alkaline water conditioning agents are added to the

detergent to soften the water, thus increasing the efficiency

of the surfactant. These builders maintain alkalinity that

results in improved

cleaning. Alkaline

solutions at

temperatures indicated by the appliance industry range can

etch bare silicon similar to the bulk micromachining

process. Thus bare silicon could be adversely affected by

exposure to these liquids [16].

FAILURE MECHANISMS

The failure mechanisms that can affect sensors and

actuators are similar to that for electronic devices. These

failure mechanisms provide a means of categorizing the

varIous

effects

caused

chemical,

mechanical,

electrical, and thermal environments encountered. An

understanding of the potential failure mechanisms should

be determined before media testing begins. The typical

industry scenario has been to follow a set boiler plate of

tests and then determine reliability. This may have been

acceptable

for

typical

electronic

devices,

but

the

applications for sensors are more demanding of a

thorough understanding before testing begins. The

sensitivity of the device to its physical environment is

heightened for a pressure sensor. Any change in the

material properties results in a change of the sensor

performance. Failure mechanisms for pressure sensors in

harsh media application are listed below. The pressure

sensor allows a format for discussion, though the

mechanisms discussed are applicable in some degree to

all sensor and actuator devices.

Corrosion

Corrosion has been defined as any destructive result of

a chemical reaction between a metal or metal alloy and its

environment [17]. Several metal surfaces exist within a

pressure sensor package: metallic lines on the die,

trimmable resistors, bonding pads, wires, leadframes, etc.

Much of the die–level metal is protected by an overlying

inorganic passivation material (e.g., PECVD silicon

nitride);

however,

unless

some

package–level

encapsulant is used, bondpads, wires, and leadframes are

exposed to the harsh media and are potential corrosion

sites. Furthermore, an energized pressure sensor has a

voltage difference between these exposed metallic

surfaces, which compounds the corrosion problem.

Generally, corrosion problems are organized into the

following

categories:

uniform

corrosion;

galvanic

corrosion, and localized corrosion (including, crevice

corrosion, pitting corrosion, etc.) [17]. The factors that

contribute to corrosion are: the substrate (metallic)

material and its surface structure and composition; the

influence of a barrier coating, its processing conditions

and/or adhesion promotion; the cleanliness of the surface,

adhesion between a coating and the surface, solution

concentration,

solution

components

(especially

impurities and/or oxidizers); localized geometry and

applied potential. In addition, galvanic corrosion is

influenced by specific metal–to–metal connections.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

MPXM2102AS 数据表(PDF) 26 Page - Motorola, Inc

MPXM2102AS 数据表(HTML) 26 Page - Motorola, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载