The making of PCB involves different steps, technologies, and terms, and TG is one such term that refers to the Glass Transition Temperature. High TG PCB is the board made at a high temperature. We will discuss this topic in detail, including the TG value, features, applications, materials, parameters, and much more.
What is High TG PCB?
If a PCB’s temperature goes beyond a set TG value, its condition will change. Like, the solid board will turn rubbery, affecting a PCB’s function. Depending on where you use a PCB, the temperature of the application should be at least 10 to 20C less than the PCB temperature.
Understanding TG Value
TG means Glass Transition Temperature like there is a certain limit of this temperature for PCB and that specific temperature is the TG value. TG value helps in understanding the PCB material, and you can find which temperature is required for its service.
Secondly, it helps you to find the condition of the PCB material, like if it’s solid, flexible, or solid-flex.
High TG PCB and Its Features
You have to choose a high TG Printed Circuit Board for your application carefully, because it involves multiple features, including thermal, electrical, mechanical, and chemical features.
Thermal Features: they include the TG or Glass Transition Temperature, thermal conductivity, thermal temperature’s coefficient, and decomposition temperature. TG is the temperature at which the state of the PCB material changes. But, when the board cools down, it gets back to its initial condition.
Electrical Features: they include the surface resistance, electrical power, volume relativity, and the dielectric constant and loss tangent.
Chemical Features: the chemical properties of a high TG PCB include the moisture absorption and the methylene chloride resistance of the PCB material. The TG PCB should be able to resist moisture if it’s near water.
Mechanical Features: the mechanical features are also important to know regarding the TG PCB. They include the flexural and peel strength, and the young’s module.
Suitable Materials for High TG PCB
A PCB has two materials, including laminate and substrate. The substrate includes epoxy resin, glass, or paper weave. The substrate should be compatible with the TG. Some common substrates that we use for a high TG PCB are;
- CEM-1, 2, 3,4, and CEM-5
- G-10 and 11, FR-1 to FR-6
The last three materials are flexible.
The laminates should also be compatible with your TG PCB in terms of strength and temperature. Some common laminates are:
- FR-1, and FR-4
- CEM-1, CCEM-3
Criteria for High TG PCBs
Printed circuit boards with a high TG value are based on certain criteria as described below:
- The selection of a PCB, depending on the components like it can be single or double-sided PCB or embedded.
- The stack-up PCB with a single layer or several layers
- The design of such boards can be based on a module or it can be custom
- The strength of the board also matters, like it should be robust either electrically or mechanically
- PCB’s bendability also helps to classify the TG PCB, like if it’s hard, flexible, or hard-flexible
- The electrical strength also helps classify the TG PC Board
Generally, manufacturers use bendability and strength to classify a TG PCB‘s physical properties.
Where Can You Use The High TG PCBs?
You can use the high TG circuit boards in intense conditions, as the environments with high-vibration devices. They are also suitable for applications with shocks, chemical components, and high temperatures. Like, missiles and car parts often come up with chemicals. So, the suitable industries for high TG PCBs include aerospace, telecommunications, military and defense force, automobile, and down-hole drilling.
What to Consider While Designing a Rigid PCB?
You must hire a professional PCB manufacturer for the right design, manufacturing, and assembly of these boards. The engineer must know the kind of environment that suits a TG PCB to function precisely. Below are a few examples to help you understand it.
Many telecommunication companies use the best materials for mobile devices to enable them to bear high shocks. Like, the phone should not get damaged easily when you drop it.
PCB has to be safe under a car’s hood as it’s mostly vibrating, so a shock or crash might happen. Hence, a rigid PCB is the best solution in this case.
The flying machinery always needs the high TG PCB because there is intense vibration, like in the jet engine, as there are thousands and millions of micro-vibrations in one minute. So, equipment related to aerospace should be able to tolerate extreme temperatures, like from -45°C to 85°C.
These boards are also ideal for solar power equipment, such as power inverters and cogeneration equipment. As these boards resist temperature, they work well in many industries. Like, one of its applications involves Lead technology, like the medical, computer, and telecommunication industries.
The TG PCB is also used in broadcasting, like booster stations. Besides, the fire detectors and burglar alarms also need such boards.
Use of High TG Flex PCB
It is clear from the name that a flex PCB can adapt any design or shape to get compatible with certain products. Like, they can tolerate intense environments better than rigid PCBs. You can use the high TG flex PCB in defense and military, aerospace, medical equipment, consumer electronics, auto, wireless networks, as well as industrial equipment.
What To Consider While Designing a Flex PCB?
You must hire a professional PCB manufacturer for the right design, manufacturing, and assembly of flex PCB. The engineer must know the kind of environment that suits a TG PCB to function precisely. You should see if:
- You need a flex PCB for an ordinary environment or an extreme environment like an explosion. Whereas the cell phone has a normal environment.
- The environment should be free from any moisture before installing a high TG circuit board.
The Design Process
The design of a high TG PCB involves different steps, such as
- Using the right software, like CAD, Eagle, Altium Designer, etc.
- You must know the power requirements to suit different components on the PCB. You should also consider a specific plan for noise reduction caused by a TG PCB.
- Preparation of the stack-up plans documents as it is essential for making the best TG PCB.
- The floor layout for a PCB with proper sections, including components. Like you can place them together or separately.
- TG PCB should be complete in terms of a power plane and ground details. These details ensure proper routing for signals.
- The board should be compatible with patterns in terms of sizes. All components should be well-placed to help a PCB function the right way.
- It is important to design routs for high-frequency signals, as the route should be clear for a flawless signal transfer. This step involves vias, as they help in proper signals. You need the reverse via and signal via in this case.
- You must follow the 3W-rule to increase the traces’ distance which helps to reduce the coupling effect.
- Another rule to reduce the coupling effect is the 20 H rule.
- In the end, check the routing guidelines to see if you are doing everything the right way.
Specs and Design Parameters
The fabrication of a high TG PC Board Fabrication involves certain parameters and specs, depending on the application. Some standard parameters are described below.
How Many Layers Do You Need
Designers prefer the even number of layers while developing the high TG PCBs. But, the odd numbers of layers are also suitable in certain applications.
Dimensions of PCB
The PCB dimensions depend on its application. Like, you need a large circuit board for a broader application. Besides, there should be enough space on the board to place the electrical components.
The high TG PCB should be well-finished, and the material depends on where you want to use this board. Like, some common materials are;
HASL, or hot air leveling – It is ideal as it is cheap and can be stored for longer.
OSP, or organic protective surface
Immersion silver – It gives a smooth surface, and it is cost-effective. It has many storage limitations
Immersion tin – It suits the SMT
Immersion gold – It can be stored for longer with a few limitations.
ENEPIG, nickel palladium – It can be stored longer, but it involves a complex process.
Solder mask – It protects the PCB from environmental elements.
Weight of copper – You must also consider the weight of copper like it includes both initial and finishing copper. Generally, the weight is 1 oz. to 1.5 oz. or 5 oz. It also depends on the layer and board thickness.
Assembled PCB thickness – The TG PCB thickness depends on its material and type. Like, if it’s flexible, hard, or a hard-flex board.
Distance between layers – The distance or spacing of electrical components and layers should be equal for high-frequency signals. As it reduces the coupling effect.
Via sizes – The drill aspect ratio and the hole size should also be appropriate. Generally, the PG PCB can have either plated-through or non-plated through holes, depending on the placement and layout design.
Board quality – The board should have a high-grade material to ensure an effective function during application. Besides, you must check the quality of the TG PCB to evaluate its performance in terms of specs. Like, you should test its lamination, vias, copper plating, solderability, finishing, components, and cleanliness.
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