M24308/23-5F D-Sub Connector: Engineering Specs and Selection Guide
M24308/23-5FThe M24308/23-5F is a 50-position D-Sub receptacle from Amphenol Interconnect India, designed for panel-mounted, solder-terminated applications requiring a female socket interface. This connector belongs to the MIL-DTL-24308 family, a specification that governs D-Sub connectors for military and aerospace use, and is categorized under D-Sub Connector Assemblies. For engineers specifying high-reliability I/O in harsh environments, the core engineering challenge is balancing contact density, current capacity per pin, and environmental sealing without sacrificing signal integrity. The M24308/23-5F addresses this with a 5-shell size (DD layout) providing 50 signal contacts rated at 7.5 A each, gold-plated for corrosion resistance, and a steel shell with yellow cadmium plating for EMI shielding and galvanic compatibility with aluminum chassis.
Working Principle of the D-Sub Connector Family
D-Sub connectors establish separable electrical connections using parallel rows of pin or socket contacts housed in a D-shaped shield. The asymmetric D-profile ensures polarization, preventing reverse mating. The M24308/23-5F uses stamped and formed female socket contacts that accept male pins from a mating plug. These contacts rely on a spring-beam mechanism to maintain normal force against the pin, ensuring consistent metal-to-metal contact pressure. The steel shell with yellow cadmium plating provides low-impedance grounding and attenuates electromagnetic interference (EMI) when the connector is fastened to a chassis ground. Solder termination transfers the signal from the PCB or wire to the contact body, with the throughput hole mounting stabilizing the connector against mechanical vibration.
Critical Parameter Analysis of M24308/23-5F
When evaluating this connector for a design, engineers should cross-reference datasheet values with system requirements for current derating, contact resistance, and insulation integrity. The table below consolidates the defined specifications and generic engineering interpretations.
| Parameter | Value | Engineering Meaning |
|---|---|---|
| Connector Style | D-Sub | Defines I/O form factor, pin spacing (0.108 inch row-to-row), and polarization via D-shape. |
| Connector Type | Receptacle, Female Sockets | Accepts male pins; rear side of connector is typically installed on fixed panel or PCB. |
| Number of Positions | 50 | Total signal contacts; layout is 2 rows x 25 pins for DD shell size. Higher pin count requires precision alignment. |
| Mounting Type | Panel Mount, Through Hole | Mounting flange with through-holes secures connector to a cutout; solder tails pass into PCB or wire. |
| Shell Size | 5 (DD, D) | Shell size 5 (DD) corresponds to 50-position layout. Mechanically compatible only with same shell size. |
| Contact Type | Signal | Not designed for power or coax; current per contact limited to signal level (7.5 A typical rating). |
| Flange Feature | Housing/Shell (Unthreaded) | Flange holes lack threads; must use separate nuts/bolts for mating. Consult datasheet for screw size. |
| Termination | Solder | Leads are soldered to wire or PCB. Requires proper flux cleaning to avoid corrosion on cadmium shell. |
| Shell Material, Finish | Steel, Yellow Cadmium Plated | Cadmium provides sacrificial corrosion protection and low contact resistance to ground. Note: RoHS compliance may be limited. |
| Contact Finish | Gold | Gold over nickel underlayer ensures low contact resistance (typically under 30 mΩ after 500 cycles). Thickness per MIL-DTL-24308. |
| Material Flammability Rating | UL94 V-0 | Insulator will self-extinguish within 10 seconds. Required for commercial and military safety compliance. |
| Current Rating (Amps) | 7.5 A | Maximum continuous current per contact at 30 °C ambient derated for all 50 contacts energized simultaneously. See datasheet for thermal derating curve. |
| Dielectric Withstanding Voltage | Consult datasheet | Typical MIL-DTL-24308 range is 1000-1500 Vrms between contacts and shell for 60 seconds without flashover. |
| Insulation Resistance | Consult datasheet | Specified at 5000 MΩ minimum per MIL-DTL-24308. Drops sharply with moisture ingress. |
| Contact Resistance | Consult datasheet | Initial contact resistance for gold-plated contacts typically below 7 mΩ. After 1000 cycles, expect below 20 mΩ. |
| Operating Temperature | Consult datasheet | MIL-DTL-24308 parts normally rated -55 to +125 °C. Cadmium finish may outgas if exceeded. |
| Mating Cycles | Consult datasheet | Military-spec D-Sub families are designed for 5000 cycles minimum while maintaining contact resistance. |
The current rating of 7.5 A per pin must be derated when all 50 contacts carry current simultaneously. The standard derating factor for D-Sub connectors is 0.6 to 0.7, meaning a practical per-pin limit near 5.25 A. Exceeding this without forced convection or heat sinking can cause contact temperature rise above the insulator rating of 125 °C, leading to thermoplastic creep and pin retention loss. The gold contact finish is another critical parameter: MIL-DTL-24308 requires a minimum gold thickness of 0.76 μm over a nickel barrier. Thinner gold or missing nickel exposes copper, which oxidizes after 100-200 mating cycles and elevates contact resistance above the typical 30 mΩ limit.
Selection Methodology for High-Reliability D-Sub Connectors
Selecting the correct D-Sub connector for an application involves matching shell size, contact density, termination style, and environmental protection. The M24308/23-5F fits the DD shell layout (50 positions in 2 rows) with a row-to-row pitch of 0.108 inches and contact spacing of 0.090 inches. For designs requiring 7.5 A per pin, confirm that the total power dissipation (P = I2R × N contacts × derating) stays under the connector's natural convection limits. If the system involves hot-swapping, specify gold-over-nickel plating to prevent arcing degradation. For outdoor or salt-fog environments, specify the cadmium-plated shell for corrosion resistance, but verify local RoHS and REACH regulations since cadmium is restricted in many consumer and automotive applications.
Real-World Applications and Industries
The MIL-DTL-24308 family, including the M24308/23-5F, is extensively used in defense electronics such as radar systems, avionics LRUs, and portable communication terminals where high pin count and vibration resistance are required. In industrial automation, D-Sub connectors appear on PLC I/O cards, servo drive interfaces, and test equipment backplanes. The 50-position layout is common for parallel data buses and multi-channel analog signals. Aerospace applications include cabin management systems and flight deck instrumentation, where the cadmium shell ensures electromagnetic compatibility with aluminum airframes. However, for new designs in Europe, yellow cadmium is being phased out in favor of tin-zinc over steel; engineers should consult the latest M24308/23-5F datasheet for alternatives.
Common Field Pitfalls with D-Sub Connectors
Premature failure in D-Sub connectors often arises from incorrect crimping or soldering, moisture ingress, or counterfeit plating. For solder-terminated parts like the M24308/23-5F, flux residue left on the cadmium plating can promote galvanic corrosion. Always post-clean with isopropyl alcohol and verify with ionic contamination testing. Moisture ingress through unsealed shell flanges degrades insulation resistance from 5000 MΩ to under 100 MΩ; if outdoor installation is planned, apply a gasket or specify a sealed backshell. A common counterfeit indicator is gold plating that flakes after 50 mating cycles — measured contact resistance exceeds 50 mΩ. Engineers should inspect the mating face under 10x magnification for a distinct yellow hue from the nickel barrier under bright gold. For high-speed serial signals above 1 Gbps, the D-Sub's unshielded contacts can radiate EMI; ensure a 360° shielded backshell is used.
Frequently Asked Questions About M24308/23-5F
Frequently Asked Questions About M24308/23-5F
What is the difference between M24308/23-5F and M24308/24-25F?
The M24308/23-5F is a 50-position receptacle (female socket), while the M24308/24-25F is a 50-position plug (male pins). Both share the same DD shell size and solder termination, but the plug has pins that mate with the receptacle sockets.
Where can I find the M24308/23-5F datasheet?
Download the current M24308/23-5F datasheet from your distributor's product page. The datasheet includes the mechanical drawing, contact layout dimensions, temperature derating curve, and recommended PCB hole pattern.
Can the M24308/23-5F be used in RoHS-compliant designs?
This part has a yellow cadmium-plated steel shell. Cadmium is exempt from RoHS only for certain aerospace and defense applications. For RoHS-compliant designs, consider equivalent parts with tin-zinc plating or black tin-nickel finish.
How do I verify that an M24308/23-5F connector is genuine?
Authentic parts have laser-etched part numbers on the shell, smooth gold contact surfaces with distinct nickel underlayer, and insulator material marked with UL94 V-0. Counterfeits often show irregular die-cast edges, thin gold (<0.5 μm), and missing corner radius on the D-shell.
Technical Takeaway for Design Engineers
The M24308/23-5F is a well-characterized military-grade D-Sub receptacle offering 50 gold-plated contacts in a cadmium-steel shell. When integrating this part, derate the 7.5 A per-pin rating to 5.25 A for full population, ensure solder flux removal to avoid galvanic attack on the cadmium finish, and verify that your application's signal frequency stays below the D-Sub's typical 100 MHz bandwidth. For cross-reference, the M24308/23-5F is mechanically interchangeable with other MIL-DTL-24308 DD-shell receptacles from Glenair and ITT Cannon, but verify contact position numbering before ordering. Always request the manufacturer's test report for contact resistance and dielectric strength when lot acceptance is critical.
