Well-seasoned PCB manufacturers know that each circuit board type comes with its thermal, chemical, and mechanical properties. High TG PCBs are intended to work in environments with high operating temperatures (equal to or above 170°C).
The ability to work under extreme temperatures requires High TG boards to have good thermal stress resistance. Let’s find out what makes such PCBs usable for certain types of electronic products.
The basic laminate material used for producing PCB is FR4. It’s a flame-retardant fiberglass reinforced epoxy material regarded as a standard option for PCB manufacturing. It’s cheap, usable, and can withstand up to 115°C only. High TG modification is what enhances its feasible thermal load to new heights.
You probably have heard about the basic classification of FR4 PCBs, based on the number of copper traces in a board:
Standard FR-4 uses bromine, a halogen elemental that is fire resistant. This laminate material offers a good resistance-weight ratio, adequate moisture resistance, good mechanical strength, and an impressive insulating capacity.
FR-4 succeeds in the matters of compatibility with other components, space-saving, design and flexibility, impedance control, and other parameters. Every its strength, especially temperature requirement, may be emphasized by TG modification.
The Glass Transition Temperature (TG) is one of the most essential qualities that resin epoxy material may have. It’s a rather mechanical property in opposite to a chemical or electrical one.
TG designates a transition temperature to a polymer or glass, depending on the base material. This is the point at which the material starts changing from a solid to a rubber state. Materials that exceed their TG points do not melt but rather become that rubbery material by undergoing structural changes on the molecular level.
Here are some of the characteristics that High Glass Transition temperature grants you laminate materials with:
The mentioned are applicable to TG material overall, while High TG PCBs may have additional properties.
Take a look at what the transfer from solid state to rubber state looks like on the example of TG materials in the image below.
Here is the pool of materials that you may use in the production of high TG PCBs:
Other types of materials may also be applicable. Their array is being added on and off.
The natural specificities of TG are crucial. But manufacturers are more interested in what characteristics their High TG PCB should have:
Every of the mentioned parameters of TG boards is superior to regular FR-4 PCBs.
You also should pay close attention to several other characteristics of TG materials. It’s important that they have adequate heat dissipation to avoid getting thermal shocks. Here are the three ways in which heat is dissipated in your electronics:
If you placed your devices with TG PCB in a well-aerated area and took other safety precautions, the lifespan of your device will be prolonged. It’s so because the PCB will be dissipating heat better.
Let’s proceed with reviewing the advantages that High-TG materials and PCBs made of them bring to your manufacture.
Due to excellent TG PCB’s mechanical resistance and chemical resistance, they can stabilize operating conditions within a device. The lifespan of boards and, consequentially, electronics also increases. TG PCBs reduce the risks of short-circuiting and other common ways in which PCBs may fail.
Another interesting thing about High TG boards is that they suit high-density designs perfectly. Such boards usually have issues with heat dissipation, and TG materials help to cope with this problem to a certain extent. So, they can be used in microelectronics having strict temperature resistance requirements.
As a rule, multi-layer and HDI PCB boards have dense circuits that minimize the route along which electricity flows. It results in low levels of convective heat dissipation and, therefore, increases the internal temperature. Once again, TG materials are less prone to such adverse effects.
When you expect a thermal load of more than 25°C below the TG point of PCB, it’s advisable to replace your FR-4 laminates. The same is for cases when a device may be operating with an internal temperature of more than 130°C. For these occasions, you should consider getting high TG boards that would perform perfectly under such conditions.
Another crucial aspect is the technological migration to RoHS PCB. These are board with lead-free soldering. It requires higher temperature levels to melt and flow. Only High TG material can withstand laminating with RoHS solder paste.
Probably you may consider replacing all your FR-4s with high TG boards. But since it’s a costly intervention, here are the industries in which the use of high glass transitions boards is obligatory:
There are additional scopes of application for TG, and you can always find ways to implement them.
High glass transition temperature boards are the modified standard PCBs. They are needed, in the first place, for electronics that operate under high-temperature conditions. The thermal stresses shorten the lifespan of PCBs, while TG materials help to increase board capacity.
There is a vast array of applications in which TG boards are irreplaceable. These include controllers, computer systems, high-frequency electronics, and more. It’s highly advised to get the most out of TG materials in these applications for the best manufacturing outcomes.
Need any help with PCB or PCBA manufacturing? Contact us now.
PadPCB is a professional PCB solution supplier in Shenzhen, China. We help our clients with everything from PCB design to the final mass production….