High Tg PCBs

At extreme temperatures, standard printed circuit boards can soften, warp, or even melt, and the electrical properties most likely will not work correctly. That’s where high Tg printed circuit boards come in.

What is High Tg PCB?

Tg refers to the high heat resistance in PCB raw materials. Here’s a useful guide to classifying printed circuit boards based on temperature resistance:

Standard copper-clad laminate PCBs: Between 130°C and 140°C
Middle Tg PCBs: Greater than 150°C
High Tg PCBs: Greater than 170°C with a typical range of 180°C to 225°C

There are many materials, such as rigid and flex polyimide material, with an average Tg of 220°C. Hydro-carbon ceramic-filled substrate has a temperature greater than 280°C and Teflon-based laminates have a temperature of >300*C.

A high Tg PCB contains a resin system that’s designed to withstand lead-free soldering and enables higher mechanical strength in harsh, higher temperature environments. Resin refers to any solid or semisolid organic substance that’s often used in plastics, varnishes, etc.

In other words, if your PCB has a higher Tg, it has more stability and a better chance of resisting heat, moisture, chemicals and other characteristics that would otherwise render the PCB ineffective.

In recent years, more and more PCB customers are requesting to manufacture their projects with high Tg due to its resiliency, high mechanical strength, and ability to withstand harsh environments.

Now let’s explore high Tg characteristics, materials, and key considerations when it comes to the two main types of circuit boards: rigid and flex.

High Tg Rigid PCBs

High Tg components are used in both rigid and flex PCBs, and despite the many similarities between the two, there are some distinct differences. A rigid circuit board, as the name implies, means it cannot bend or move out of shape — in other words, inflexible.

Applications for High Tg Rigid PCBs

High Tg printed circuit boards are used in harsh environments — in other words, applications and devices with a lot of vibration and shock, extreme temperatures, or certain chemical components, such as car parts, the inside of missiles, or jet engines.

They are often used in the following industries:

Telecommunications
Down hole drilling
Aerospace
Defense and military
Auto

High Tg Capabilities for Rigid PCBs

Cirexx fabricates and assembles high Tg printed circuits boards with every high Tg material on a regular basis.

Design & Test

2 mil trace width, 3 mil air gap, IPC class 2/IPC class 3, Flying probe net list test, Differential impedance, TDR testing, Automatic optical inspection

Drill & Rout

Counter sinks/counter bores, Scoring/rout and retain, Laser route, Blind vias/buried vias, Stacked vias

Lamination

1-30 layers, Vacuum lamination, Sequential lamination

Plating

Conductive via fill, Non-conductive via fill, Plated edges, Plated radii (castellation), Plated milling cutouts, Hard gold body, Soft bondable gold, Immersion gold, Immersion silver, HAL standard, HAL lead-free (ROHS), ENTEK (OSP)

Materials

Flex and rigid-flex, Kapton™ and non-Kapton, RF and high-speed materials, Mix materials/FR-4-Teflon, Metal back boards (LED/power distribution ), Heavy Cu 6 oz. finish rigid and rigid-flex

Cirexx Fabrication Capabilities

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Key Design Considerations for Rigid PCBs

It’s important to work with the right PCB provider when it comes to the proper layout, fabrication, and assembly of high Tg printed circuit boards. The designer needs to understand what kind of environment is needed for the PCB to work correctly. Here are some examples:

Commercial: Cell phone providers like Apple and Samsung spend considerable amounts of time selecting the right material so that your phone has a better chance of surviving a shock (i.e. being dropped).
Auto: Printed circuit boards need to survive under vehicle hoods since the car is always vibrating and there’s the potential for a great shock, such as a crash.
Aerospace: Any piece of equipment or machinery that flies needs a high Tg printed circuit board; jet engines, for example, produce thousands and thousands of micro vibrations per minute. Aerospace equipment needs to withstands temperatures of -45°C to 85°C.

High Tg Flex PCBs

As the name implies, flex PCBs can be shaped and designed to fit into certain products or systems. There are three types of flexible circuits:

Applications for High Tg Flex PCBs

Flex circuits are designed to withstand harsher environments and higher temperatures than rigid PCBs. Flex circuit boards are used in the following environments and industries:

Aerospace and military
Consumer electronics
Optoelectronics
Medical
Industrial controls
Wireless networks
Auto
Wearable electronics

Key Design Considerations for Flex PCBs

Here are some things to keep in mind as you consider high Tg flexible PCB design:

Operating environment: Is your flex circuit designed for a non-extreme environment, such as a cell phone, or the highest of extremes, such as an explosion?
Assembly: You want to make sure all moisture is removed before the circuit is subjected to high temperatures.

Cirexx has the technology, deep engineering experience, and knowledge to help you design and build a high Tg PCB from the start. If you have questions about a high Tg PCB or what type of resin system you need for your project, contact us, and we’ll get back to you shortly.

Looking for a High Tg PCB Quote?

We use a well-organized process and the right software to provide you with a quote within 24 hours. After you upload your information, including any fabrication drawings or schematics, our system and engineering staff will analyze the data and provide us with a comprehensive document so we can take a closer look at your project.

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