Key Takeaways (Executive Summary)
- The Standard: Aerospace and Defense contracts almost universally require IPC/WHMA-A-620 Class 3workmanship—the highest standard for "High Performance Electronic Products."
- Security: Manufacturing for defense often requires ITAR (International Traffic in Arms Regulations) registration to ensure technical data is not shared with foreign nationals.
- SWaP: The engineering priority is Size, Weight, and Power (SWaP). We use lightweight Tefzel (ETFE) wire and composite connectors to shave off grams.
- Traceability: Counterfeit avoidance is critical. Every component must have a verifiable paper trail back to the franchised distributor.
- Where Failure is Not an Option
In consumer electronics, a bad cable is a warranty return. In the automotive industry, it's a recall. In Aerospace and Defense, a failure can result in the loss of a mission or the loss of life.
Manufacturing Mil-Spec (Military Specification) cable assemblies is the pinnacle of the interconnect industry. It requires a manufacturing environment that goes beyond "quality" and focuses on absolute reliability and strict legal compliance.
If you are sourcing harnesses for avionics, drones (UAVs), or defense systems, generic manufacturing standards do not apply. Here is the framework you need to understand.
IPC/WHMA-A-620: Class 2 vs. Class 3
The global standard for cable assembly workmanship is IPC/WHMA-A-620. It is divided into three classes. Most industrial products are Class 2. Aerospace is strictly Class 3.
Class 3 Definition: "Products where continued high performance or performance-on-demand is critical, equipment downtime cannot be tolerated, end-use environment may be uncommonly harsh, and the equipment must function when required."
Comparison Table: Class 2 vs. Class 3 Criteria
How strict is the inspection?
|
Inspection Criteria |
Class 2 (Industrial/Auto) |
Class 3 (Aerospace/Mil) |
|---|---|---|
|
Solder Fill |
50% vertical fill of the barrel is acceptable. |
75% minimum vertical fill is required. |
|
Wire Damage |
Minor nicks in insulation allowed if verified. |
Zero insulation damage or burns allowed. |
|
Strand Damage |
Some nicked/scraped strands allowed (<5%). |
Zero nicked or scraped strands allowed. |
|
Shield Termination |
Flexible criteria for pigtails. |
Strict criteria for 360-degree shielding. |
|
Visual Inspection |
Sample based (AQL). |
100% Inspection of every connection. |
The Regulatory Landscape: ITAR and AS9100
Building a cable for a tank or a fighter jet involves legal hurdles that normal manufacturers cannot clear.
- ITAR (International Traffic in Arms Regulations): This is a US government regulation. If a drawing is marked "ITAR Restricted," a manufacturer cannot share that file with anyone who is not a US Person. The facility must be registered with the Directorate of Defense Trade Controls (DDTC).
- AS9100: This is the aerospace equivalent of ISO 9001. It adds specific requirements for configuration management (handling revision changes) and FOD (Foreign Object Debris) control.
SWaP: The Obsession with Weight
In aerospace, every ounce of weight costs fuel to lift. Therefore, Mil-Spec harnesses look very different from industrial ones.
- Wire Insulation: We rarely use PVC. We use ETFE (Tefzel) or PTFE (Teflon). These materials are incredibly tough, allowing for extremely thin insulation walls that save weight and space.
- Connectors: Instead of heavy stainless steel, we use Composite (high-grade plastic) circular connectors or Aluminum with Cadmium or Nickel plating.
- Small Gauge: It is common to work with 26, 28, or even 30 AWG wire to transmit data, requiring microscopic crimping precision.
- Counterfeit Avoidance and DFARS
The defense supply chain is a target for counterfeit parts. A fake $50 connector can ground a $50 million aircraft.
To combat this, we adhere to DFARS 252.225-7014.
- We buy exclusively from Authorized/Franchised Distributors (like Powell, TTI, Avnet).
- We require a CoC (Certificate of Conformance) for every component.
- We never buy from the "grey market" or unauthorized brokers, even if the part is out of stock elsewhere.
Frequently Asked Questions (FAQ)
Q: What is "Outgassing"? A: In the vacuum of space (or high altitude), standard plastics release gases (outgas) that can fog up sensor lenses or optical equipment. Space-grade cables must use low-outgassing materials (verified by ASTM E595 testing).
Q: What is FOD control? A: Foreign Object Debris (FOD) control means keeping the manufacturing area spotless. A tiny snipped piece of wire or a solder splash left inside a connector shell can cause a short circuit during flight. We use specific "Clean as you go" protocols.
Q: Do you use lead-free solder for Mil-Spec? A: Surprisingly, No. Many Mil-Spec contracts explicitly require leaded solder (Sn63/Pb37). Why? Because lead-free solder can grow "tin whiskers"—microscopic crystals that can cause short circuits over time. Lead suppresses this growth, making it safer for long-term mission reliability.
About the Author
Michael Wang
Senior Technical Engineer
As the technical lead at TeleWire, Michael bridges the critical gap between complex engineering requirements and precision manufacturing. With deep expertise in Design for Manufacturing (DFM) and signal integrity, he oversees the technical validation of custom interconnect solutions for mission-critical automotive, industrial, and medical applications.
