settinginfinidock

ApplicationsEngineeringNote:AEN-0103CADKDOCApplicationoftheTypeCHRHighResistancePrecisionChipResistorsWhenusingtheTypeCHRresistorthreefactorsarekeytooptimizingtheperformanceofthishighresistanceprecisionchipresistor:Temperature,CircuitBoardLayout,andSolderAttachment.
Thesehighresistanceprecisionchipresistorsaredesignedforuseinextremelylowsignaldetection/amplificationcircuits.
Thedesignercanchoosefromanumberofavailablestandardresistancevaluestooptimizethecircuitdesign.
ApplicationsincludePhotodiodesignalamplification,photomultipliers,ionizationdetection,etc.
Theseprecisionhighresistancechipresistorscanalsobeidealforuseastheinputresistorforhighimpedancevoltagedivisionandgainsetting.
OperatingTemperaturevs.
optimizedperformance:TheTypeCHRHighResistancePrecisionChiphasaverylowtemperaturecoefficientrelativetotheoperatingtemperature.
Forresistanceof10Megupto25Megthelow±25ppm/°Cappliesoverthetemperaturerangeof–40°Cto+85°C,referencedto+25°C.
Forresistancevaluesabove25Megthetemperaturecoefficientisdefinedintwotemperaturerangestohelpinoptimizingperformance.
AtemperatureCoefficientof±35ppm/°Cappliesfrom+10°Cto+40°C,referencedto+25°Cand±70ppm/°Cappliesoverthetemperaturerangeof–40°Cto+85°C,referencedto+25°C.
Formaximumstability,theproductshouldbeoperatedinanambienttemperaturebelow+85°C.
OperatingStability,TCperformancevs.
circuitboardlayout:TheTypeCHRHighResistancePrecisionChipResisorhasexcellentTemperatureCoefficientandstabilityspecifications.
Toachievethebestperformanceitisimportanttominimizethecontributionofcircuitboardissuesrelativetohighresistanceleakage.
TooptimizethelayoutforthischipresistorthecircuitboardshouldhaveaslotdesignedintheboarddirectlyundertheresistorelementtoprovideforenhancedcleaningunderReleaseDate:03/12/03,Rev.
A,Rev.
Date:03/12/03Page1of1CADKDOCCaddockElectronics,2003AcopyofthisApplicationNotecanbeobtainedatwww.
caddock.
comthishighresistancechip.
Additionally,theslotwillprovidehighinsulationresistance,providedbythe"slot",theairgap.
Theslotwillalsoreducecapacitivecouplingtothecircuitboardfromthechipresistorelement(theFlipChip"FCStyle"chipresistor'selementfacestowardtheboardsurfaceinthesolderingofthisresistortothecircuitboard).
Thereshouldnotbeanycoppertraceinthelayoutdirectlyundertheresistor(theslothelpstopreventthisdesignerroraswell).
(SeeFig.
#1forcircuitboardlayoutsketch).
StyleFC–FlipChipVersionforsurfacemountapplications.
Thisversionhassolderablemetallizedterminationpadsononesideofthesubstrate,thesamesideastheresistiveelement.
ThebacksideofthesubstrateisbareceramicSolderattachmentnote:Therecommendedsoldersforflipchipsolderattachmentare62Sn/36Pb/2Ag,96.
5Sn/3.
5AgorstandardSn/Ag/Cusolderalloys.
CHIPRESISTORSOLDERPASTE(REFLOWED)FLIPCHIPSOLDEREDONCIRCUITBOARDCIRCUITBOARDCIRCUITBOARDCIRCUITBOARDTypicalslotwidthisaminimumof1.
5timesthechipresistorwidth.
Fig.
1Slotthroughcircuitboard