Background

Capacitors for space flight use are procured using the requirements set forth in various MIL specifications.  These specifications are specific to the type of capacitor and provide various product assurance requirements.  It is important to select the type of capacitor based on the specific use of the part.  Each type of capacitor has specific advantages and disadvantages for a given application.  

Major Issues

The selection of parts manufactured to the individual military specifications is limited.  Military parts have specific requirements for reliability and various parameters that limit the capacitance and voltage ratings for a given part size.  Commercial Hi-Rel parts offered by manufacturers may provide a higher level of capacitance per volume but this is at the expense of other parameters.  Careful consideration should be given to the limitations of these parts.  Non-military parts should be procured using a Specification Control Drawing rather than relying on manufacturer data sheets.  Data sheets can be changed without notice and are not reliable for defining a part over time.  SCDs should be based on the appropriate military specification in order to obtain the product assurance level desired.

Some of these parts can be damaged during the installation process.  Extreme care should be taken when mounting these devices.  Capacitor manufacturers provide general precautions and instructions for their product and should be contacted when dealing with special mounting conditions. 

Sources of Information

EEE-INST-002 has a section on capacitors.  This publication replaces 311-INST-001.

Documents and References

The following documents detail requirements for military capacitors.

• MIL-PRF-20 Capacitors, Fixed, Ceramic Dielectric (Temperature Compensating), Established Reliability and Non-Established Reliability, General Specification for (CCR)
• MIL-PRF-81 Capacitors, Variable, Ceramic Dielectric, General Specification for (CV)
• MIL-PRF-123 Capacitors, Fixed, Ceramic Dielectric (Temperature Stable and General Purpose), High Reliability, General Specification for (CKS)
• MIL-PRF-14409 Capacitors, Variable (Piston Type, Tubular Trimmer), General Specification for (PC)
• MIL-PRF-39001 Capacitors, Fixed, Mica Dielectric, Established Reliability and Nonestablished Reliability, General Specification for (CMR)
• MIL-PRF-39003 Capacitors, Fixed, Electrolytic (Solid Electrolyte), Tantalum, Established Reliability, General Specification for (CSR & CSS)
• MIL-PRF-39006 Capacitor, Fixed, Electrolytic (Nonsolid Electrolyte), Tantalum, Established Reliability, General Specification for (CLR)
• MIL-PRF-39014 Capacitor, Fixed, Ceramic Dielectric (General Purpose) Established Reliability and Nonestablished Reliability, General Specification for (CKR)
• MIL-C-49464 Military Specification, Capacitors, Chip, Single Layer, Fixed, Parallel Plate, Ceramic Dielectric, Established Reliability, General Specification for (CMS)
• MIL-PRF-49467 Capacitor, Fixed, Ceramic, Multilayer, High Voltage (General Purpose), General Specification for (HVR)
• MIL-PRF-49470 Capacitor, Fixed, Ceramic Dielectric, Switch Mode Power Supply (General Purpose and Temperature Stable), General Specification for (PS)
• MIL-PRF-55365 Capacitor, Fixed, Electrolytic (Tantalum), Chip, Nonestablished Reliability, Established Reliability, General Specification For (CWR)
• MIL-PRF-55681 Capacitor, Chip, Multiple Layer, Fixed, Ceramic Dielectric, Established Reliability and Non-Established Reliability, General Specification for (CDR)
• MIL-PRF-87164 Capacitors, Fixed, Mica Dielectric, High Reliability, General Specification for (CMS)

Check manufacturers web sites for applications and technical information.