High Frequency Laminate Measurements
There is no standard platform to evaluate high frequency PWB materials, and there are several methods for measuring properties such as dielectric loss. Furthermore, there is no definition of moisture for any of these tests and moisture can significantly change a test result. Suppliers and OEM’s need to work together to evaluate test methods and characterize materials.
Halogen free materials have become a focus in the PCB industry in the last few years. Many materials have been developed and tested and more are appearing all of the time.
Halogen free materials are attractive not only because of their being "green material" but also because of some of their chairacteristics. Typically halogen free materials have a lower dielectric loss than many other materials. This gives them an advantage in applications where high speed signals are used. They do have one draw back however, they are typically more expensive than FR-4 materials.
One of the problems the industry has been faced with is the multitude of test methodologies used to measure dielectric loss and dielectric constant. The test methodology difficulity is the same for non halogen free and halogen materials.
HDP User Group has run several projects evaluating standard FR-4 material, halogen free material, and lead free material. This project is a continuation of that work. We will use loW loss non-halogen free material and halogen free material in our testing. The purpose of the project however is not to publish another material evaluation, the purpose is to evaluate and characterize the test procedures.
Note: The term “halogen-free” used herein refers to bromine or brominated compounds not being used in the resin formulation (i.e. not added to provide flame retardant properties to the finished laminate material).
Some of the problems with laminate material characterization, halogen free or not, is that there is no industry agreement on the best way to measure the material attributes, particularly dielectric constant and dielectric loss. The industry standards allow for multiple test methodologies and procedures. The material suppliers have different approaches to measurement techniques and the OEM's have different approaches. This leads to general confusion for everyone.
Electrically test commonly used high frequency (< approx. 0.010 Df) laminate materials, including commercial “halogen-free” laminate materials, using all viable electrical test methods. Test at speeds above 2 GHz. for example 3GHz, 5Ghz, 10GHz, and 20GHz. This project will evaluate and compare the 8 or 9 most common test methods, including SPP, SET2DIL, Bereskin, S3, EBW and more.
The team will write a report that describes the test method differences, variances, and capabilities.