Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

industrial length for the microstrip transmission line

industrial length for the microstrip transmission line

industrial length for the microstrip transmission line

hi all I made a design and in it after optimization I had a microstripp transmission with width 0.3 mm , can this be manufactured plz inform me

RE: industrial length for the microstrip transmission line

On FR-4 material you can get down to about 0.10 mm (4 mil, 0.004") trace widths.  

RE: industrial length for the microstrip transmission line

OH, and the tolerance is about +/-1 mil (0.025 mm) so make sure you take that into account on the transmission line.  

RE: industrial length for the microstrip transmission line

A microstrip of 0.3mm (.012 mil) is no problem on FR-4 for in a general use RF design (I assume you are on FR-4). Actual width may depend even upon how old the gerber photoplotter your board vendor uses, and how consist his process is from run to run.

Other factors for FR-4 (which I assue you are using) are dielectric variations lot-to-lot, the actual frequency of the signal (dielectric varies slightly with frequency), actual weight of the copper (copper thickness) and the prepreg glass content of a multilayer board.

Assuming your 0.3mm is on a multilayer (would have to be if it's 50 Ohm) the required width may vary with how much the copper is pressed in the prepreg in the lamination phase, which then again is dependent upon the glass/resin ratio for the particular prepreg(s) used to obtain the desired thickness. Then again, dielectric constant can vary slightly from one FR-4 manufacturer to another

Then again, many of the forumulas used to calculate the width of a microstrip are only approximations, and they vary when compared against each other.

What I'm trying to get at is there are a lot of approximations in getting to a solution for impedance matched traces on a PC board. You get close and that's fine for 90% of all designs. Unless you are working on a Teflon substrate, and measuring afterwards with a network analyzer to adjust your design, what you end up with is only a approximation.

RE: industrial length for the microstrip transmission line

It is OK to manufacutre such a width.

The only think you have to consider before you will order your PCB is what type of software did you use for optimization. If it wasn't any real 3D or at least 2.5D simulator so You have to expect that measured results compared with simulations will be more or less (depending on working freq.) shifted.

RE: industrial length for the microstrip transmission line

This all sounds like good information here so I would like to ask a question without starting a different post.
What do you think the advantages and disavantages of FR-4 vs polyimide for microstrip work in the sub 2 GHz range?  Also, is there something other than a genenric FR-4 to get lower variation in RF properties between batches or even vendors on FR-4?

RE: industrial length for the microstrip transmission line

Well, the only advantages of FR-4 is that it is cheap and it is good enpugh for RF circuits.
Disadvantages are changing RF properties depending on vendor. Problem is that every vendor prepare the whole material itself. Compared with for example ROGERS materials, which are very stable despite the vendor, all materials needed for preparing of PCB needs to be bought from ROGERS.

You should also keep in mind that FR-4 is more lossy then other materials. But it is nothing wrong sometimes. Thanks to it You can achieve better backward isolations, better return loss in wider freq. range, spurious signals on higher freq. are more attenuated etc. etc.

Other alternative which is a bit better then FR-4 and not so expensive as ROGERS and other teflon materials is BT-epoxy. But, sincerly, I have no idea who is using it nowdays. MAybe someone from this forum have same info?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close