High Frequency Flex minutes-040915

Minutes of April 9, 2015 Meeting(10:00 AM Central)


Project Leader:  Geoffrey Hazelett, Polar Instruments.


Project Facilitator:    John Davignon, HDP


Present on the call:

Geoffrey Hazelett, Polar (Lead)

Joe Smetana, Alcatel-Lucent

Glenn Oliver, DuPont

Swapan Bhattacharya, Engent

John Davignon, HDP

Holle Galyon, Multek

Farhad Razavi, MFlex

Neil Chamberlain, Polar

Ken Thomas, Polar


Next Meeting:  April 23, 2015 @ 10 AM CT


Meeting Agenda:

 ·         Continue discussion on Problem Statement and start to focus project goals/objectives.

·         Decide if we are going to evaluate both flex and rigid-flex designs

New Action items:

·         Glenn will send to me some material property information and Johnd will upload to the website.

·         Glenn will ask Tony Senese if he will share some materials data with the team.

·         Johnd will contact Vicki Ragogna, Rogers about Non-Flow adhesives and interest in the project


  Johnd opened the meeting and explained the ground rules for participating, including the IP and non- disclosure rules of HDP User Group.


Geoffrey started the discussion with the Problem Statement. This sparked a lot of good conversations about the problems seen in the industry and which ones we might want to address first.

It was mentioned that there are 4 projects stated in our present Problem statement, we will need to rank these as we progress.

The four statements from the project proposal are as follows:

1.       Controlling the geometries of flexible materials as they differ from rigid PWBs.

2.       The differing properties of the materials (Dk, Df etc.) involved and the fact that some dielectrics and adhesives are very hygroscopic.

3.       Cross hatch GND planes. Simulating the effect of the non-contiguous plane and the effect of various shapes.

4.       The use of Tatsuta shielding and other shielding approaches like metalized films. Used as an EMI shield in many applications but has effect on the signal integrity of the transmission line.

 Design/Geometry Questions:

Geometries are much smaller in the Flex industry. Some work in this area has already been done by Glenn. The objective data for #1 is very hard to come by.

Polar is interested in controlling the characteristic impedance through geometry.

The frequency and the length of the trace is very important. Short lines do not worry about impedance.

 The fabricators use cross hatch to limit the ground plane due to the thin laminate and thin lines and for controlling the impedance.  Return paths are a big problem with cross hatch planes, hard to model. Most use a solid plane. Cross hatching in flex is mostly done for impedance, but in the US it is also done for flexibility (Military applications).

Glenn said that crosshatching is tribal knowledge and approach to do this is often proprietary.

Polar has the ability to validation to models with various structures and designs.  Glenn stated that the industry needs this information as he sees a lot of homegrown designs.

 Joe asked if there was a literature search done or information of what has been done to date? Glenn said that it is mostly proprietary and he cannot share his data.

 Materials Properties:

Farhad said that the issue we have been discussing are ones that he has seen and is seeing. He is interested in the #2 statement, the differing materials properties part. He does not see that the data sheets match the real life.  He would like to validate the models and the materials.

 The copper profile and etching really effects the signal and that this is often wrongly contributed to the laminate material. Glenn thinks this is not a laminate issue but a copper/fabrication implications.

 Glenn has some material property information that he has (published and non-published) up to 10 GHz (using a resonator). He has transmission lines data also on RA vs. ET copper. Note: Rolled copper surface profile has the same roughness as Electrodeposited but has better signal integrity. Glenn will share this with the team.

 The hygroscopic nature is also very hard to get. The water moves very quickly in and out of the adhesive.  In the 10 minutes of testing the property can change in moisture %. (1-1.5 GHz is where water gets to be a concern)

 Swapan would like to define the frequency range we are interested in evaluating.


Next Meeting:  April 23, 2015 @ 10AM CT