The Ultimate Operating Phenomena of Mil Spec PCB

21 Jan, 2022

By ren

When military PCBs are manufactured, they are divided into several classes based on their quality. Any board produced for IPC Class III has satisfied the most stringent criteria for mission-critical PCBs used in industries such as aerospace, military equipment, military arms regulations, and medical applications, based on tight minimum tolerances and extremely high accuracy standards.

Reaching these specified criteria assures that the PCB will last a long time, tolerate difficult situations, and function at a high level without fail. As a result, these boards are incredibly dependable, as they are built with extreme accuracy and little tolerance.

Military Spec printed circuit board

A military-spec board must be built from the ground up, according to military specifications or IPC 6012 class 3/A. The design, layout, material selection, and manufacturing procedures should all adhere to strict guidelines. Qualified manufacturers create military PCBs and can deal with exacting specifications and tolerances.

Mil Spec Pcb Industry and DoD Standards

The military standard covers the requirements for DoD standards. An interface, standard procedures, design criteria, test technique, and the production process are all part of this.

If you don't account for essential PCB design layout issues, you can wind up with a design that doesn't transition well to the real world. Furthermore, if you don't get the layout right the first time, you'll have to redo it, leading to production delays and additional expenditures.

Board Size and Functionality

You'll need to make sure there's enough room on the printed circuit board. The size of the board is determined by the size of the final product, the functionality the board must provide, and other variables. Electronic devices, as well as the printed circuit board on which they are built, are shrinking. Estimate the board's size before you begin the design process. If a more conventional design does not provide enough room for all of the functionality necessary, you may need to utilize a multilayer or high-density interconnect (HDI) architecture.

Reliable for Harsh Conditions

Because of the demanding working circumstances, Printed Circuit Boards (PCBs) used in aerospace and military applications must be highly reliable. These circuit boards, unlike conventional PCBs, are subjected to harsh environments, chemicals, pollutants, and other impurities.

These PCBs must comply with IPC-A standards, which are designed for high-performance

electronic devices. The requirements demand that electrical equipment work continuously in hostile settings with no downtime. As a result, military and aerospace PCBs require particular production, design, and assembly considerations. These concerns and uses of these PCBs in military and aerospace equipment are discussed in this essay.

Applications of Mil-spec PCBs

These have vast applications in:

·       Vehicles that are not crewed

·       Navigation and communication systems for the military

·       Automated systems

·       Embedded processors in satellite subsystems

·       Computers that have been toughened

·       Mortars and artillery

·       Protection and security at the base/camp

Design Considerations for Military and Aerospace PCB Assembly

Any PCB construction follows a pre-determined layout. It's the same with aircraft and military PCB assembly. However, some unique design considerations are considered to achieve IPC requirements.

All components should meet Mil-spec requirements. The tolerances on these components are incredibly tight, ranging from 1-2 percent. Tolerances of 5-10% are standard in commercial grades, which is not advised.

How the PCBs are built to withstand the highest current load possible?

Low-frequency and high-frequency components are distinguished clearly. Waveforms are produced

by some high-frequency components, which may alter the low-frequency components. The waveforms add noise to the signal and lower its quality, unsuitable for military and aerospace applications. Clock signals should be protected and free of interference. Physical shielding is created at the design stage to achieve this.

Material enclosures composed of aluminum or similar materials generate physical shielding. Because it helps to survive high temperatures, quality heat resistant materials are utilized. Wherever heat dissipation is required, thermal compounds should be employed. Pre-layout simulations and impedance is performed to understand how the PCB will operate in actual situations.

Thermal Management

Components that produce a lot of heat require more clearance space than typical components. As a result, while mounting, care should be given to improve their clearance space. It preserves the PCB by preventing neighboring elements from overheating.

For enhanced solderability, braided and stranded wires should be pre-tinned. To prevent vibration, press-fit components are soldered. Before starting the assembly, double-check the thermal profiles for the wave and reflow soldering procedures. During the assembling process, this helps to avoid component damage.


The finishing material is chosen so that it aids the PCB's performance in hostile environments. The following are some of the most commonly used finishing products for this purpose:

·       Nickel and gold electrolysis

·       Immersion Gold Coated Electroless Nickel (ENIG)

·       HASL without lead

·       Silver Immersion

·       Gold that can be electrolytically bonded

·       HASL

For PCB conformal coating, acrylic-based sprays are utilized. This aids in the protection of the final PCB.

Validation of design

To validate these PCB design, high-quality software simulation programs should be employed. This aids in verifying loads at various areas and understanding design changes that need to be performed.

PCB routing should be kept at 45-degree angles or slightly less. This aids in the smooth transfer of electricity across the circuit.

Manufacturing Processes

It would help if you also thought about the manufacturing methods you want to make the board. Each approach has its own set of limits and constraints. You'll need to utilize reference holes or locations on the board that is compatible with the manufacturing process. Always make sure there are no components in the pits. Keep the mounting technique for the board in mind as well. Depending on your strategy, you may need to leave different panel portions open. Using several technology types, such as through-hole and surface mount components, can raise the cost of your boards, but it is sometimes required. Always double-check with your fabrication to be sure they can build the sort of board you require.

Material Component

Consider the materials and components you want to employ for your board during the layout step. You must first ensure that the requested goods are available. Some materials and parts are complex, while others are prohibitively expensive. Different components and materials may have varying design requirements.

Ground and Power Planes

One of the most essential PCB layout design principles is to keep your power and ground planes within your board. They should also be centered and symmetrical to prevent your board from bending and twisting. Due to bowing, components may shift out of place, potentially damaging the board. Using standard rails for each supply, ensure you have dependable, comprehensive traces, and avoid forming daisy chains to connect components.

Voltage Dependency and Mil Spec boards

Low-voltage and current control circuits can be harmed by high voltage in power circuits. You may reduce interference by strategically placing your power ground and control ground. Separate the settings for each power supply step as much as possible.

Signal Integrity and Radio Frequency Issues

PCB layout design is critical for maintaining signal integrity and avoiding electrical

like radio-frequency interference or electromagnetic interference.


The way you route your traces has a lot to do with avoiding these issues. Avoid running tracks parallel to each other to prevent signal problems. Parallel tracks will have increased crosstalk, leading to complex issues once the PCB is completed. If paths cross over one another, ensure that they do so at right angles. As a result, the capacitance and mutual inductance between the lines will be reduced, lowering crosstalk. Signal integrity is improved by using semiconductor components that emit less electromagnetic radiation.

Thermal Problems

Thermal concerns might impact many different aspects of the design process. Larger boards with higher component density and processing rates are more prone to heat-related issues. They may not be a problem for smaller boards, but they can be a significant difficulty for more complex ones.

Allowing heat to disperse is necessary to avoid heat-related disorders. Identify components that produce a lot of heat first. The thermal resistance values for each element should be listed in its datasheet. Then, follow the specified rules to deflect heat away from that component.

Technetronic Advantages

When it comes to Military Circuit Boards, you can't just trust any PCB Assembler. Long development cycles need the use of a military systems PCB Manufacturer with substantial experience in military PCB fabrication and quality control systems. It is what Technetronic offers.


Take your time to make sure you've picked the best materials and components for your board, as well as designing a board that makes use of their qualities. We are preferred Military PCB providers with over four decades of experience in both manufacturing and assembly of complicated PCBs. Besides, we have a collection of industry best practices in PCB fabrication, board thickness, quality solder mask manufacture, solder support, the business manufactured project, and edge project.


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