What is MIL-PRE-55310?

MIL-PRF-55310 is a U.S. military performance specification that defines the general requirements for quartz crystal oscillators used in electronics for military applications. This specification outlines requirements for materials used in oscillator construction, package and lead finishes, interface, and physical dimensions, as well as performance metrics such as frequency stability, accuracy, phase noise, random vibration, harmonic and subharmonic distortion, and environmental resilience (temperature, vibration, shock, humidity, etc.). The MIL-PRF-55310 standard also specifies test methods (e.g., electrical tests, thermal shock testing, vibration testing, acoustic noise testing, etc.) and procedures for screening and qualification inspections to ensure oscillators are suitable for mission-critical applications. 

Manufacturers supplying crystal oscillators to the U.S. military must comply with the MIL-PRF-55310 standard to ensure that their components perform reliably and can withstand the harsh conditions found in military operations. This standard is used by the U.S. Department of Defense (DoD).  

The MIL-PRF-55310 standard applies to the following oscillator types:

• Crystal Oscillators (XO)
• Voltage Controlled Crystal Oscillators (VCXO)  
• Temperature Compensated Crystal Oscillators (TCXO)   
• Oven-Controlled Crystal Oscillators (OCXO)  
• Temperature Compensated/Voltage Controlled Crystal Oscillators (TCVCXO)  
• Oven-Controlled/Voltage Controlled Crystal Oscillator (OCVCXO)  
• Microcomputer Compensated Crystal Oscillator (MCXO)  
• Rubidium-Crystal Oscillators (RbXO)  
• Surface Acoustic Wave Oscillators (SAWO)

This military standard is revised periodically to ensure that it remains current with technological advancements. MIL-PRF-55310F is the current edition (As of October 21, 2024).

Additional information: 

According to the MIL-PRF-55310 specification, oscillator manufacturers are required to have their products listed in the Qualified Products List (QPL) prior to being awarded a contract. To be included in the QPL, the manufacturer must establish and maintain a QPL system that ensures products undergo all required qualification testing, including environmental, mechanical, electrical, and performance tests as specified by the qualifying activity (QA). MIL-STD-790 standard specifies the requirements of the QPL system. 

 The qualifying activity (QA) is generally a government agency or an accredited testing organization that conducts evaluations, tests, and verifications of products to ensure compliance with all qualification requirements specified in this standard. If the product meets all the necessary standards, the QA will issue a certificate authorizing the product's listing in the QPL. 

Also, to retain qualification, the contractor must provide verification of the following requirements every 24 months: 

• MIL-STD-790 program. 
• Oscillator Design has not been modified. 
• Screening tests, conformance tests, and periodic tests have been conducted in accordance with the specifications outlined here. 
• The contractor maintains the capability to manufacture and test oscillators to this specification. 
• Continued qualification to product level C shall be based on continued maintenance of qualification for product level B. 

If no production during this period, the contractor must confirm to the qualifying activity that they still can manufacture and test the QPL oscillator and express their intent to remain on the QPL.