Hermetically Sealed Military Relays and Contactors

Updated October 13, 2026

Relay types and where each one is used

Pick the specification from the contact current first, then the package and whether the relay must hold its position with no coil power. The three general specifications split the current range, and each one covers latching and nonlatching designs through its slash sheets.

MIL-PRF-6106 defines a relay contactor as a relay whose main contacts are designed to switch high amperage power, considered to be 25 amperes or more, typically to distribute power from the source to the load bus or between buses. Contactors often carry auxiliary contacts for low current switching, which the same specification describes as 5 amperes or less, driven by the same actuator. When a relay goes into a harness or a power distribution box, see our wire harness sourcing page for how the assembly side is handled.

The specifications that govern military relays

The general specification sets construction, test and quality requirements, and each slash sheet defines one relay family. Revisions below are the latest we read on EverySpec in October 2026; confirm the current revision on ASSIST before you release a drawing.

MIL-PRF-6106P classifies relays by type: Type I is continuous duty, hermetically sealed; Type II is continuous duty, unsealed; Type III is intermittent duty in hermetic, environmentally sealed or unsealed forms; Type IV is continuous duty, environmentally sealed but not hermetic. The same document notes that class O relays from the old MIL-R-6106B no longer meet the specification and that existing class O standards are kept only for government replenishment spares.

How the part number is built: M39016/10-001L

An established reliability relay part number has four fields, and the last letter is the failure rate level. MIL-PRF-39016G gives this exact example, and MIL-PRF-83536D uses the same layout with M83536 in front.

Table I defines the levels in percent failures per 10,000 cycles:

The levels are established at 90 percent confidence for qualification and 60 percent for maintaining qualification, based on 100,000 cycles at +125 °C under rated load. The specification notes the rate assumes an average of 10 cycles per hour for 1,000 hours under MIL-STD-690. With acquiring activity approval, a relay qualified to a better level may be substituted for a worse one, for example P for M, but relays shall not be remarked unless the contract allows it. Qualified relays are marked with a JAN or J brand above or below the M.

MIL-PRF-6106 relays carry no failure rate letter. Its PIN is M6106, the sheet number and a dash number, for example M6106/20-001, and relays still covered by MS or AN standards keep the PIN format of those standards.

Contact ratings and the load you actually switch

A relay rating is only valid for the load type it was tested with, so match resistive, inductive, motor and lamp loads separately. MIL-PRF-39016 and MIL-PRF-83536 define three contact load ranges:

• Low level: 10 microamperes at 50 millivolts to 10 milliamperes at 6 volts.
• Intermediate: 10 milliamperes at 6 volts to 100 milliamperes at 28 volts.
• High level: above 100 milliamperes at 28 volts.

The 25 ampere ratings in MIL-PRF-83536 apply to resistive loads only; motor, inductive and lamp ratings on those sheets are lower. MIL-PRF-6106 adds application cautions a designer should read before choosing a part:

• Capacitive loads. The inrush into a capacitor can weld contacts. The specification recommends analyzing circuit impedance and choosing a relay whose motor load rating is greater than 18 percent of the peak switching current. It also warns that low break current on capacitive dc loads builds up contact material that can lock contacts closed, shortening life.
• 115/200 volt ratings. These mean a three phase system. The relay may not interrupt 200 volts across a single set of contacts; ask the manufacturer before using it that way.
• Transfer contacts. Do not use them to transfer loads between phases or between unsynchronized ac sources.
• Coil voltage. All three specifications carry the caution that any coil voltage below rated will compromise operation. MIL-PRF-39016 adds that pickup, hold and dropout voltages are test values, not design criteria.

Latching relays, construction and mounting styles

A latching relay holds its last position with the coil off, and its main hazard is the magnetically neutral state. The specifications require two coil latching relays to be designed so that energizing both coils at once does not leave the contacts in neutral, and they screen for it. In service, MIL-PRF-39016 and MIL-PRF-6106 say the latch and reset coils should not be pulsed together, should not be pulsed below rated voltage, and the pulse width should be at least three times the specified operate time.

Construction requirements explain why these parts last and why counterfeits fail:

• Hermetic seal. Relays are dried, degassed, backfilled and sealed by welding. MIL-PRF-39016 sets a standard leak rate of 1 x 10^-6 atm cm³/s of air per MIL-STD-883 Method 1014.
• Prohibited finishes. MIL-PRF-39016 prohibits pure tin, zinc plating and cadmium plating inside and outside the relay, because of whisker growth, and prohibits silicone compounds for any purpose.
• Plug-in pins. Gold plating for plug-in terminals is called out to ASTM B488 over a nickel underplate.
• Dissimilar metals. Contact couples are limited to those permitted by MIL-STD-889.

Mounting and termination are set by the slash sheet. MIL-PRF-39016 describes mounting brackets that must be an integral part of the relay, solder pin wire leads, and plug-in pin terminals that mate with a socket. The manufacturer may hot solder dip terminals or shorten leads as optional value added services when the purchase order says so. If you need a bracket, header plate or enclosure machined to carry a relay, that can ride on the same order; see CNC machining.

Space grade screening: EEE-INST-002 Section R1

For NASA Level 1 and Level 2 work, a military relay is acceptable only with added process controls. EEE-INST-002 Table 1 says MIL-PRF-39016, MIL-PRF-6106 and MIL-PRF-83536 relays are acceptable for Levels 1 and 2 if they are procured to failure rate M or better where applicable, the lot was subjected to small particle cleaning and internal inspection during assembly, and the lot passes particle impact noise detection (PIND) afterwards. For Level 2, three random samples may instead pass destructive physical analysis (DPA) per GSFC S-311-M-70, without residual gas analysis.

Table 2 of the same section lists the screening flow for relays bought outside those specifications, including:

• Cleaning and small particle inspection to the manufacturer's approved procedure, Levels 1 and 2.
• PIND at all three levels.
• Internal moisture detection: insulation resistance of at least 10,000 megohms before and after energizing the coil at 140 percent of rated voltage for 2.5 minutes.
• High temperature soak and low, high and room temperature run-in with low level contact loads, 2,500 cycles per run-in for Level 1.
• Radiographic inspection per MSFC-STD-355C for Level 1.
• Fine leak at 1.0 x 10^-8 cc/s and gross leak testing, Levels 1 and 2.
• A percent defective allowable of 5 percent for Level 1 and 15 percent for Level 2.

EEE-INST-002 treats relays rated up to and including 2 amperes dc resistive as low level and anything higher as high level. It also prohibits pure tin as a final finish or undercoat and calls for header glass inspection at 10x or more. For how relay grades fit the wider parts program, see EEE parts grades.

What to put on the purchase order

• Full PIN exactly as drawn, including slash sheet, dash number and failure rate letter, for example M39016/10-001L.
• General specification and slash sheet with revision, or a statement that the revision in the contract applies.
• Qualified source: a manufacturer listed in DLA's Qualified Products Database for that sheet, bought from the manufacturer or its authorized distributor.
• Whether failure rate substitution is allowed, and that parts shall not be remarked.
• Lot or date code traceability on the certificate of conformance and the package label, with a single date code if your program requires it.
• NASA level and any added screening, PIND, DPA or lot data, with the data delivered.
• Optional services you want, such as hot solder dip or lead trimming, stated explicitly.
• Packaging that protects leads and headers; ESD packaging when the relay has internal diodes that are not part of the coil circuit, which MIL-PRF-39016 says may be ESD sensitive.
• DFARS counterfeit clauses and any prime flow-downs that apply.

Our certificate of conformance page explains what the cert should state.

Counterfeit and quality risks, and how to receive relays

The common relay problems are remarked failure rate letters, wrong dash numbers with the same footprint, old date codes sold as new, and opened or reworked cans. Military relays are also a long tail item: many slash sheets have few qualified makers, so legacy programs end up buying from brokers. DFARS 252.246-7008 defines electronic parts as integrated circuits, discrete electronic components and circuit assemblies; a relay is not named, so whether your contract treats it as covered is a question for your contracts team, though many buyers apply the authorized source rule anyway. Our counterfeit parts avoidance guide covers the clauses and AS6081 brokers.

At receiving:

• Read the marking character by character against the PO, including the JAN or J brand, failure rate letter and date code.
• Check the circuit diagram on the can against the slash sheet; the specification requires it as a terminal view.
• Inspect header glass and terminals under magnification for cracks, chips and solder rework. EEE-INST-002 lists blisters, foreign material, dark spots, cracks and chips as irregularities to look for.
• Look for evidence of a reopened can, such as a disturbed weld seam or adjunct sealant where the drawing does not allow it.
• Match lot and date code on the part, bag and certificate, and hold parts whose paperwork does not tie to the lot.

See receiving inspection for the dock routine and certs and traceability for the paperwork chain.

How we source relays and contactors

We do not stock relays, publish prices or act as an authorized or franchised distributor for any manufacturer. We source the PIN on your drawing through the manufacturer or its authorized and franchised distributors, flow your failure rate, screening and data requirements down in writing, and check the certificates against the PO before shipment.

• Relays bought alone or kitted with sockets, brackets and harness parts per assembly.
• Relays combined with harness builds, machined brackets or ground support equipment on one purchase order.
• Inactive slash sheets and out of production relays chased under counterfeit-avoidance controls; see obsolete aerospace parts.

Related electromechanical parts: circuit breakers and switches, motors and actuators, sensors and transducers, or the electromechanical overview. For the connectors that usually sit next to them, see circular connectors.

Request relays or a relay kit

Send the full PINs, quantities, NASA level or screening flow, and whether failure rate substitution is acceptable through the harness and electromechanical quote form. Those details decide which qualified sources can supply the part under your contract. A person replies within one business day, and every order ships with a certificate of conformance. For defense and launch programs with controlled drawings, read how we handle files and controlled programs first.

Questions

Related

• Aircraft Circuit Breakers, Toggle Switches and Sensitive Switches
• EEE Parts Grades: From Commercial to Space Level
• Aerospace Circular Connectors: MIL-DTL-38999 and Its Relatives
• How to Buy Obsolete Parts Without Buying Counterfeits

Sources

• MIL-PRF-39016G, Relays, Electromagnetic, Established Reliability (25 Aug 2014), EverySpec
• MIL-PRF-83536D, Relays, Electromagnetic, Established Reliability, 25 Amperes and Below (2 Jan 2013), EverySpec
• MIL-PRF-6106P w/Amendment 1, Relays, Electromagnetic (22 May 2017), EverySpec
• EverySpec FSC 5945 index, Relays and Solenoids (MIL-PRF-28776E listing)
• NASA/TP-2003-212242, EEE-INST-002, Section R1 Relays, Electromagnetic (May 2003)
• Acquisition.gov, DFARS 252.246-7008 Sources of Electronic Parts