Established Reliability Resistors and Capacitors
Established reliability (ER) resistors and capacitors are military passives whose failure rate is proven by ongoing life testing and coded in the part number as a failure rate level. The main specs are MIL-PRF-55342 chip resistors, MIL-PRF-55681 and MIL-PRF-123 ceramic capacitors, and MIL-PRF-55365 tantalum chip capacitors.
Updated
Types and where they are used
Four DLA specifications cover most of the surface mount passives on aerospace and defense boards. Each has qualified sources on a qualified products list, and the part number carries the reliability level.
| Style | Part | Spec | Typical use |
|---|---|---|---|
| RM | Fixed film chip resistor, non ER, ER and space level | MIL-PRF-55342 | Surface mount and hybrid circuits, precision dividers, pull ups |
| CDR | Multilayer ceramic chip capacitor, ER and non ER | MIL-PRF-55681 | Decoupling, filtering and timing on military boards |
| CKS (M123) | High reliability ceramic capacitor, leaded and chip, BX, BR, BP and BG dielectrics | MIL-PRF-123 | Space, missile and other high reliability boards |
| CWR | Solid tantalum chip capacitor, ER | MIL-PRF-55365 | Bulk capacitance on power rails where moisture protection is available |
For commercial and automotive passives, the reference is AEC-Q200, the Automotive Electronics Council's stress test qualification for passive components. It qualifies a part family; it does not assign a failure rate level or screen each lot.
The specifications and their status
| Spec | What it covers | Status as listed on EverySpec |
|---|---|---|
| MIL-PRF-55342 | Fixed film chip resistors: non ER, ER with life failure rates from 1 percent to 0.001 percent per 1,000 hours at 60 percent confidence, and space level | Active, revision H with Amendment 4 (January 2016) |
| MIL-PRF-55681 | Multilayer ceramic chip capacitors, ER levels from 1.0 to 0.001 percent per 1,000 hours at 90 percent confidence, life tested at 200 percent rated voltage with an 8:1 acceleration factor | Active, revision F (September 2004) |
| MIL-PRF-123 | High reliability ceramic capacitors for space, missile and other high reliability uses, life tested at two times rated voltage | Active, revision E (April 2020) |
| MIL-PRF-55365 | Solid tantalum chip capacitors with exponential FRLs at 60 percent confidence or Weibull FRLs down to 1 FIT at 90 percent confidence | Active, revision H (February 2011) |
| AEC-Q200 | Stress test qualification for passive components | Revision E base document per the AEC |
EverySpec mirrors may lag the official record, so confirm the current revision on DLA's ASSIST database and the qualified sources on the qualified products database before you place the order.
Have a part like this?Send it in under a minute. A person replies within 1 business day.Failure rate levels: what M, P, R, S and T mean
The failure rate level (FRL) is the letter that states the proven life failure rate, and each step is ten times better than the last. For MIL-PRF-55342 and MIL-PRF-55681, NASA's parts selection list gives:
| FRL | Failure rate per 1,000 hours | NASA level noted on the NPSL |
|---|---|---|
| M | 1.0 percent | Level 3 (MIL-PRF-55681) |
| P | 0.1 percent | Level 2 |
| R | 0.01 percent | Level 2 |
| S | 0.001 percent | Level 1 |
| T (MIL-PRF-55342) | Space level, see below | Level 1 |
Tantalum chips use a different letter set. For MIL-PRF-55365, NASA lists Weibull grades B at 0.1 percent, C at 0.01 percent and D at 0.001 percent per 1,000 hours, with B at Level 2 and C and D at Level 1. NASA-STD-8739.10 sums it up: Grade 1 passives are FRL T, S or R, and C or D for tantalum; Grade 2 are R, P or B.
Two cautions. The FRL is a statistical rating of the product line under life test conditions, and NASA-STD-8739.10 notes that a manufacturer's reliability value applies to the part as made and may not apply to its use in your system. And not every combination exists: NASA's application notes for MIL-PRF-55342 say all combinations of termination, characteristic, tolerance and failure rate may not be available, so check the QPL before you design one in.
Space level passives
Space level passives add screening on top of the best ER level, or come from a spec written only for space. The two common routes:
- MIL-PRF-55342 T level. NASA's application notes say T level product receives added screening and inspection at the manufacturer, such as power conditioning, and that suppliers must maintain the S failure rate level, qualify the product through 100 thermal cycles and certify outgassing to NASA Publication 1124.
- MIL-PRF-123. NASA-STD-8739.10 names it as a specification that applies only to space grade ceramic capacitors. NASA's EEE-INST-002 lists the CKS style at all three levels for use as is, with no failure rate letter needed.
Tantalum adds surge current testing. MIL-PRF-55365 offers optional surge testing at 25 °C (option A) or at -55 °C and +85 °C (options B and C). EEE-INST-002 calls for the -55 °C and +85 °C method from MIL-PRF-55365/4 at Level 1 and the 25 °C method at Levels 2 and 3, so put the option letter on the PO rather than leaving it blank.
How the part numbers are built
Each of these decodes comes from NASA's parts selection list ordering pages.
M55342K02B10E5S, a chip resistor: M55342 is the specification prefix (the RM1206 style uses D55342); K is a ±100 ppm/°C temperature characteristic; 02 is specification sheet /2, style RM0505; B is a solderable barrier termination; 10E5 is 10.5 kilohms at 1 percent, with E acting as both decimal point and multiplier; S is the 0.001 percent failure rate level.
CDR01BX100AKSR, a ceramic chip capacitor: CDR01 is the style from MIL-PRF-55681/1; BX is ±15 percent capacitance change over -55 °C to +125 °C; 100 is 10 pF; A is 50 Vdc; K is ±10 percent; S is a solder coated final termination; R is the 0.01 percent failure rate level.
CWR11CB225JBA, a tantalum chip: CWR11 is the molded chip style from MIL-PRF-55365/8; C is the rated voltage code from the specification's voltage table; B is a gold termination, 50 microinches minimum; 225 is 2.2 µF; J is ±5 percent; B is the 0.1 percent Weibull level; A is surge current tested at 25 °C.
M123A01BPC4R7CW, a MIL-PRF-123 capacitor: M123A01 identifies the specification and detail sheet; B is the -55 °C to +125 °C rated range and P the temperature characteristic, which together NASA lists as BP, ±30 ppm/°C; C is 100 V; 4R7 is 4.7 pF; C is ±0.25 percent; W is a solder coated copper clad steel lead.
Terminations, pure tin and tin whiskers
Pure tin finishes can grow whiskers that short adjacent conductors, so space programs ban them and many military specs require lead in the finish. EEE-INST-002 states that pure tin, cadmium and zinc shall not be used as a final finish on EEE parts. NASA-STD-8739.10 treats finishes under 3 percent lead by weight as Pb-free and lists tin, tin alloys, zinc, cadmium, indium, antimony and silver among metals that form whiskers.
The specs differ, which is why the termination letter matters. NASA's tin whisker reference table records:
| Spec | Pure tin per NASA's table |
|---|---|
| MIL-PRF-55342 | No pure tin allowed, minimum 3 percent lead |
| MIL-PRF-55365 | No pure tin allowed, minimum 3 percent lead |
| MIL-PRF-123 | Pure tin allowed on chip capacitor terminations only |
| MIL-PRF-55681 | Pure tin allowed |
For MIL-PRF-55681, NASA's ordering notes say the tin based termination codes W and Y are prohibited for space flight use. For MIL-PRF-123 chips, the Z termination is a barrier metallization with tin lead plate containing at least 4 percent lead. NASA's table reflects the date it was last updated, so read the termination paragraph of the current spec too.
GEIA-STD-0005
NASA-STD-8739.10 points programs to a lead free control plan under J-STD-001 and to SAE GEIA-STD-0005-1 for guidance. GEIA-STD-0005-2, the standard for mitigating the effects of tin whiskers in aerospace and high performance electronic systems, was first published in 2006 and revised in 2012 as SAE GEIASTD0005_2A. CALCE describes it as guidance, not a qualification standard, that assigns a control level by product criticality. Its accepted mitigations include hard potting, physical barriers, tin lead soldering with validated complete coverage, and conformal coating with validated coverage over minimum gaps that grow from Level 2B to Level 2C. Our conformal coating page covers the coating side.
Ordering checklist
- Full military part number including characteristic, termination letter, tolerance and failure rate level, plus the specification and slash sheet revision.
- Qualified source from the QPL for that spec, and manufacturer name and CAGE code.
- Termination finish stated explicitly, with a pure tin prohibition when your program requires one.
- Surge current option for tantalum, and space level options such as T level for MIL-PRF-55342.
- Manufacturer certificate of conformance and lot data, with lot date code limits and a single lot rule when your parts plan calls for them.
- Reel or tray packaging with ESD protection, labels that carry the full part number and lot, and outgassing certification where your contract requires it.
Counterfeit and quality risks for passives
Many chip resistors and capacitors carry no marking at all, so the reel label, packing slip and certificate are the part's identity. That makes a broken chain of custody harder to detect than on a marked IC. Watch for commercial parts relabeled with a military part number or a better failure rate letter, a requested combination that the QPL shows nobody makes, and reels split from their original packaging. NASA-STD-8739.10 requires buying from the manufacturer or authorized distributors unless parts are unavailable, and requires receiving inspection against the procurement documents. If a part must come from outside that chain, the testing and documentation rules on our counterfeit parts avoidance page apply, and our receiving inspection page covers dock checks.
How we source passives
We do not keep stock or publish prices. We source ER and space level passives with traceability through authorized and franchised distributors or the manufacturer, flow your failure rate, termination and lot rules down, and check every cert against the PO. Passives can be kitted with the active parts from our integrated circuits and discretes page and the bare boards from our printed circuit boards page, or shipped with a harness order. Grade selection is covered on EEE parts grades, and the full family list is on electronic components.
Quote your ER passives
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Questions
What does failure rate level S mean on a resistor or capacitor?
S is the established reliability level of 0.001 percent failures per 1,000 hours, the best of the four exponential letters M, P, R and S, each ten times better than the one before. NASA lists S as a Level 1 rating for MIL-PRF-55342 resistors and MIL-PRF-55681 capacitors. The rating comes from ongoing life testing of the qualified product line, not from testing each lot you receive.
Why do tantalum capacitors use B, C and D instead of P, R and S?
MIL-PRF-55365 offers Weibull failure rate grading, rated at 90 percent confidence, alongside the older exponential levels. NASA lists Weibull B as 0.1 percent, C as 0.01 percent and D as 0.001 percent per 1,000 hours. NASA-STD-8739.10 places C and D tantalum parts at Grade 1 and B at Grade 2. Add a surge current option letter too, since EEE-INST-002 specifies the surge method by level.
Is MIL-PRF-123 the same as MIL-PRF-55681?
No. Both cover ceramic capacitors, but MIL-PRF-123 is written for high reliability uses such as space and missiles and NASA-STD-8739.10 says it applies only to space grade parts. MIL-PRF-55681 covers ER and non ER multilayer chips graded by failure rate letter. NASA also notes that 55681 allows pure tin terminations and that its tin based codes W and Y are prohibited for space flight.
What is T level on a MIL-PRF-55342 resistor?
T is the space level option in the failure rate position. NASA application notes say T level parts get added screening and inspection at the manufacturer, such as power conditioning, and that suppliers must hold the S failure rate level, qualify through 100 thermal cycles and certify outgassing to NASA Publication 1124. Confirm qualification status with the supplier and the QPL before ordering.
How do I keep pure tin off my passives?
Specify the termination letter, not just the base part number, and add a pure tin prohibition to the PO when your program requires it. MIL-PRF-55342 and MIL-PRF-55365 already require at least 3 percent lead per NASA's table, while MIL-PRF-55681 allows pure tin and MIL-PRF-123 allows it on chip terminations. If tin finished parts are unavoidable, GEIA-STD-0005-2 lists mitigations such as coating and tin lead solder coverage.
Are AEC-Q200 passives acceptable for defense hardware?
They can be, if your program allows commercial grade parts. AEC-Q200 is a stress test qualification of a passive part family for automotive use. It does not assign a failure rate level, screen each lot or provide a QPL source. NASA-STD-8739.10 places screened automotive parts at Grade 3, so expect added screening or approval for flight or critical ground equipment.
Related
Sources
- NASA Parts Selection List, MIL-PRF-55342 part number explanation
- NASA Parts Selection List, MIL-PRF-55342 application notes (T level)
- NASA Parts Selection List, MIL-PRF-55681 part number explanation
- NASA Parts Selection List, MIL-PRF-55365 part number explanation
- NASA Parts Selection List, MIL-PRF-123 part number explanation
- NASA GSFC tin whisker site, pure tin status of EEE part specifications
- NASA-STD-8739.10, EEE Parts Assurance Standard (grades, whiskers, procurement)
- NASA/TP-2003-212242, EEE-INST-002 (capacitor requirements, surge current, pure tin)
- MIL-PRF-55342H with Amendment 4 (EverySpec listing)
- MIL-PRF-55365H (EverySpec listing)
- MIL-PRF-123E (EverySpec listing)
- CALCE, University of Maryland, Tin Whisker Mitigation webinar (October 2015), GEIA-STD-0005-2
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