Isola Fr408hr: Its Mechanical Properties and Applications

In PCB manufacturing, thermal reliability and high performance are crucial. The demands for boards that offer these features are increasing. More advanced electronics are produced overtime.

Therefore, there is the need for a thermally and electrically stable board. This article focuses on Isola FR408hr and its impacts in electronics production.

What Type of Board is Isola fr408hr?

Isola FR408hr is a high-performance prepreg system for multilayer PCB applications. FR408hr laminate are specifically produced with Isola’s high performance resin system reinforced with E-glass fabric. Also, the fr408hr is a UV blocking and laser fluorescing for great compatibility with AOI.

The fr408hr system provides 25% more electrical bandwidth. Also, it offers a 30% improvement in its z axis expansion. Also, fr408hr has great moisture resistance at reflow. Therefore, this laminate closes the gap from an electrical and thermal perspective.


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Mechanical Properties to Consider in Isola fr408hr

Flexural strength

This measures the capacity of fr408hr to withstand mechanical stress without breaking. Also, the IPC-4101 is a standard that specifies the recommended least flexural strength of various PCB materials. Therefore, Isola fr408hr’s flexural strength is 58.0 ksi in cross direction and 72.5 ksi in length direction.

Delamination time

This describes how long a PCB material can resist delamination. Delamination is the separation of resin from the laminate at a given temperature. Also, several factors are responsible for delamination. These factors include poor lamination process and thermal shock. Furthermore, Isola fr408hr’s delamination time is 60 minutes at T260. However, it is more than 30 minutes at T288.

Peel strength

This describes the bond strength between the copper conductor and fr408hr. Also, peel strength can be expressed in average conductor/load width or force for each linear inch required for separating bonded materials. Therefore, fr408hr’s peel strength after thermal stress is 5.5 lb/inch. After process solutions, the peel strength of fr408hr is 5.1 lb/inch.

Tensile Modulus

This determines the strength of fr408hr. However, it determines the stress ratio in a particular direction. Also, its measurement unit is unit/force area. Sometimes the material strength is expresses as tensile modulus. Therefore, fr408hr laminate’s tensile modulus is 3315 Ksi along cross direction.


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Other Properties of Isola fr408hr

AOI Fluorescence and UV blocking

The Isola fr408hr laminate features laser fluorescence and UV blocking. Therefore, this ensures great compatibility with automated optical inspection (AOI). Also, it provides maximal compatibility with photo-imageable solder mask imaging. Therefore, there is high accuracy during isola fr408hr fabrication and assembly.

Improved Z-axis expansion and lower loss

The Isola fr408hr system offers a 30% improvement in the Z-axis expansion. Also, it provides lower loss when compared to its counterparts.

Great thermal performance

Isola fr408hr features low CTE that ensures reliability. Also, this laminate has a 190 degree Celsius glass transition temperature. This is very high. In addition, fr408hr has a decomposition temperature of 360 degrees Celsius.

Applications of Isola fr408hr Laminate

Isola fr408hr laminate is commonly used in high-performance applications. Some of these applications include:

Aerospace and defense

Isola fr408hr plays a crucial role in aerospace and defense electronics. Also, this laminate has got features which make it highly reliable for this application. Isola fr408hr’s lead-free assembly compatibility is a great benefit for this application.

Industrial and instrumentation

The fr408hr system is ideal for use in the industrial system. This laminate is widely used for designing huge machines. Also, this laminate has great thermal and mechanical properties. Furthermore, it can also survive thermal stress. In the industrial system, most machines undergo thermal stress. Therefore, a board that can withstand thermal stress is very crucial in this application.

Communication and networking industry

The communication industry needs electrical grade boards. One of the benefits of the fr408hr not really spoken of is its signal integrity. This board has proved to eliminate signal integrity issues. Therefore, this PCB is widely used in the communication and networking industry.

Medical industry

This is another industry that uses Isola fr408hr. Some medical devices feature fr408hr. The need for high-end and high-frequency laminates in the medical industry is increasing. The Isola fr408hr offers high reliability and thermal performance.


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Desmear Process in Isola fr408hr

Desmearing is a crucial process in Isola fr408hr. This process removes debris and provides the hole walls great texture. The PCB material will generate little smear when drilled and cured properly. Also, it is easy to achieve electroless copper deposition with a well drilled hole.

In addition, resin cure impact and PCB design considerations impact the creation of debris-free hole walls. Therefore, remove 7628 to enhance the drilled hole’s quality. Also, ensure drill parameters are properly adjusted on cured fr408hr laminates.  This helps to reduce smear production. Therefore, this improves desmear performance and minimizes copper wicking in the long run.

Plasma desmear

There are different desmear methods. However, plasma desmearing is the best desmear method for Isola fr408hr. This is because it enables resin system etching with chemical resistance. Also, you can carry out this plasma desmear with a permanganate pass. However, be careful of excessive resin removal when using permanganate and plasma.

Isola fr408hr plasma desmearing, ordinary plasma gas combinations is sufficient. The plasma desmear  method provides enhanced hole quality.

Chemical desmear

Isola fr408hr features high chemical resistance. However, the absorption of solvent swellers result in fiberglass cracking between holes. Therefore, PCB manufacturers should perform chemical desmear without using solvent swellers.  However, alkaline butyl carbitol swellers are a great option.

Rules for Isola fr408hr PCB Lamination

During fr408hr lamination process, there are some rules you need to adhere to.

  • Control heat up rate within the laminating press. This helps to ensure melt flow.
  • Regulate cool down to prevent warpage.
  • Ensure the lamination temperature you are using is appropriate.
  • Ensure fr408hr prepreg is dry before lamination. Also, maintain the inner layers of fr408hr.
  • Ensure the cure time is enough to develop Tg (glass transition temperature).


Isola fr408hr laminate is widely used in various applications. This laminate employs RTF copper foil and HTE grade 3. Also, this laminate is specifically designed for circuitry applications. Isola is ideal for broadband circuit designs due to its low dissipation factor and low dielectric constant. This laminate is highly compatible with the majority of FR4 processes.

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