PCB Materials – Variables to Consider

There are multiple variables to consider when selecting a material for your design. From material producer to datasheets and key values, to a few additional key rules – we will provide you with a few variables to consider when selecting PCB materials.

Material Producer

The material producer refers to the company which produces the specific material which you want to use, for example, Dupont, Isola and Shengyi. The material producer becomes important when considering the type of board you wish to create.

High-tech prototype PCBs and complex HDI builds are often ordered through western PCB producers, where higher volume series production is often ordered through manufacturers in China. This is important because PCB suppliers in different regions have different standard material producers that they use. Specifying a Western-originated or European/US based material for a series production in China could lead to long lead times and delays in production.

Datasheets and Key Values

Datasheets for PCB materials are often easily accessible online through a simple google search of the material type. They can be quite confusing to look at as there are large amounts of information that you may not understand. So here are a few outlined key values to look out for:

First is the Tg value. This is the glass transition temperature which indicates at what temperature the base material will become unstable. Common Tg values to specify are 130, 150 and 170 degrees Celsius. It is important to consider this because if your PCB will be operating in a hot environment, then specifying an appropriate Tg could increase the longevity of the PCB.

It is also wise to consider the Td value of the material as well. This refers to the decomposition temperature of the material caused by the resin. It is often presented in a data sheet in a table along with the Tg value and other material properties.

In addition to thermal properties, it is also important to look at the electrical characteristics of the materials such as the Dk value, the dielectric constant. This is especially important to look at if you have a design with high-speed signals which requires controlled impedance traces. Additionally, it is also advisable to indicate the Dk value.

Finally, we will look at the CTI value. CTI stands for comparative tracking index and is a measure, in voltage, for the breakdown of a material. It is commonly presented as a PLC unit which is a simplified scale of voltage ranges, as seen in the table below.

When the material starts to breakdown it will lose its insulating properties and can eventually lead to short circuits in the PCB. If you are making a high voltage board or a board with potentially surging voltages, then it is important to select a higher CTI material.

Additional key rules:

Here are a few additional key rules to consider when selecting PCB materials:

·??????What do you require in construction

·??????UL approved in factories

·??????Considering lead time, materials that are too specific

To conclude, there are multiple variables to look at when selecting a material for your design. If you are designing a PCB and are unsure which materials will be best for your product, please contact us at NCAB and we can help you select the right material. This can also help us streamline the production and get the boards to you faster.

Want to know more about PCBs? Head over to our blog and read some of our latest PCB blog posts: www.ncabgroup.com/blog/

Learn more about NCAB Group, a leading global producer of printed circuit boards, by heading over to our page: www.ncabgroup.com

#pcbmaterials #materialofpcb #pcbmaterialselection #pcbarticles #pcbinformation #pcbeducation #pcbpost #pcbblog