Decreasing Bend Radius and Improving Reliability- Part II


Reading time ( words)

 
Application: Design guidelines to improve the flexibility and reliability of flexible circuits.
 
Many of the issues that arise when using a flex circuit come from a lack of knowledge about how to properly design one, especially when the circuit is required to bend. Many novices will design a circuit that calls for bending the flex in too tight of a bend radius, which can cause damage to the circuit and lower the reliability of the end product. This series of articles will focus on the seven key aspects to consider when designing for maximum durability and maximum “flexibility”. It is important to know that because flexibility is a relative term this study will instead use the term reducing bend radius. Below are two of the seven design strategies. Please see Part I and Part III for more tips!
 
3. Do not allow electroless copper as a seed layer prior to plating vias.
 
  • Also, an area to be concerned about is the type of plating your vendor uses. Some copper plating requires a seed layer of electroless copper. This seed layer becomes an ED copper layer and can lead to conductor cracking. For a tight bend radius direct metallization is the preferred plating method.
 
4. Use only Polyimide covers in the flexing area.
 
  • There are two options for applying dielectric material over copper:
A. Polyimide cover material: This is the preferred material in areas where parts will be bent. As a general rule, you will want to specify a dielectric thickness and adhesive thickness separately. A rule of thumb is that for every 1 ounce of copper thickness there is 1 mil of adhesive thickness.
 
B. Flexible Solder Mask: Flexible solder mask has a minimum bend radius of 0.4” and is not recommended for any dynamic flexing application or application where the bend radius will be tighter than 0.4”
 
Flex Circuit with soldermask after flexing

Share

Print


Suggested Items

EIPC Technical Snapshot: 5G and Loss Minimisation

03/26/2021 | Pete Starkey, I-Connect007
Bringing a specialised technical area into sharp focus, this month’s topic was “5G and the understanding of loss minimisation at the PCB level,” with papers on dielectric material, copper foil, and modelling solutions. The webinar was moderated by EIPC board member Paul Waldner managing director of Multiline International Europa, who admitted that he had managed to get a haircut especially for the occasion!

PCB Requirements for E-Mobility

03/23/2021 | I-Connect007 Editorial Team
Nolan Johnson, Barry Matties, and Happy Holden speak with Christian Klein, section manager for PCBs in the automotive electronics division, about Bosch’s recent presentation on PCB requirements of the future in regard to automotive and electro mobility trends and challenges.

With Pluritec, it’s All About Automation

03/23/2021 | Real Time with...IPC
Lino Sousa, vice president of sales with Pluritec, reviews the company’s specialist equipment ranges and discusses the benefits of automation of drilling, solder mask application and wet processing in small-batch, quick-turnaround PCB production.



Copyright © 2021 I-Connect007. All rights reserved.