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Thick Film Materials
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96% ALUMINA- The moat widely used hybrid circuit substrate material is aluminum oxide. It has excellent dielectric insulating properties mechanical strength, a relatively high degree of chemical inertness and good surface texture characteristics and it is easy to fabricate.
BERYILLIA- Beryllia (BeO) is another substrate that has long been in use for hybrid applications. The high thermal conductivity and the low electric constant make it attractive for high power and high frequency applications. However the use of BeO has been limited by two factors, the relatively high cost compared to alumina and the toxicity of BeO dust when sawed, ground or machined.
ALLUMINUM NITRIDE - The primary advantages of alliminum nitride (AIN) are the high thermal conductivity and it's close TCE match with silicon. AIN can draw heat away from a silicon device better than alumina beryllia which will substantially reduce mechanical stresses.
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General Conductor Parameters
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Gold
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.007-.007
.004-.004*
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Multilayers
Chip & Wire Inductors Au or Al Wire Bonding
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Platinum Gold
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.007-.007
.005-.005*
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Solder & Au or Al Wire Bonding
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Palladium Gold
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.007-.007
.005-.005*
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Solder * Au or Al Wire Bonding
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Palladium Silver
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.010-.010
.005-.006*
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Solder & Surface Mount
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Platinum Silver
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.010-.010
.005-.006*
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Solder & Surface Mount
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Platinum
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.010-.010
.005-.006*
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Solder & Sensors
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General Resistor Characteristics
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Parameter
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Standard
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Special**
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Resistivity Range
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10 ohm - megohm
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1 ohm - 1 Gigohm
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Tolerance
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Untrimmed
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±20%
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±10%
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Trimmed
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±1%
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±0.25%
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TCR - Absolute
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±100 ppm/C
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±50 ppm/C
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TCR - Tracking
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±50 ppm/C
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±25 ppm/C
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Resistance Ratio
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±1%
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±.5%
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Power Dissipation
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50 watts/sq. in.
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200 watts/sq. in.
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It is cost effective to use standard resistor characteristics wherever possible.
Resistors can be printed on both sides of a substrate.
Printed on top of multilayer dielectrics.
Trimmed to any value using computer-controlled laser trimming systems. Resistors can also be ratio-trimmed.
*Temperature Range: -55C to + 125C
** Technically feasible within the specific guidelines of the material used.
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Typical Properties Of Dielectrics
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There are many Dielectrics available to meet the needs of all types of circuits. They are used to build multilayers, crossovers, seal rings and solder stops.
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Dielectric Constant 1 Khz:
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6 - 15
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Dissipation Factor:
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.02% - 0.4%
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Breakdown Voltage per 25 micron thick:
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400 - 600 VAC
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Insulation Resistance:
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>1010 - >1010
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Colors:
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Blue, White & Pink
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Encapsulation
- Protects thick film resistors from environmental conditions encountered in subsequent processing, reactive organic potting compounds and overspray from air-abrasive trimming.
- Acts as a barrier to prevent wire, solder and epoxy shorts in assembly processes.
- May be used in a wide range of colors to code look-alike circuits.
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