Decreasing Bend Radius and Improving Reliability—Part I


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 phrase "reducing bend radius." Here are two of the seven design strategies (please see Part II and Part III for more tips):

1. Reduce overall thickness:

IPC guidelines typically list minimum bend radius of 6X the circuit thickness for single-sided flex, 10X for double-sided flex, and 20X for multiple layer flex. The area of focus is the thickness where flexing or bending will occur, which should be only in a location with conductors and not plated through-holes. Thickness can best be reduced by:

A. Using thinner copper

B. Using adhesive-less base materials

C. Stagger conductors

D. Specifying button plating or pads only plating

Any flex circuit with plated through-holes will need to be either panel plated or button plated. Button plating is preferred because it only plates the vias and leaves the conductors un-plated and which does not increase the thickness.

2. Use only rolled annealed (RA) copper:

There are two common types of copper; rolled annealed (RA) and electro-deposited (ED) copper.

A. Rolled annealed copper is best for achieving a tighter bend radius.

B. It is also important for you to put on your drawings the direction of the grain in relation to where the tight bending will occur.

flex.jpg

Go to Part two of this article.

Share

Print


Suggested Items

The iNEMI 2019 Roadmap: Flexible Hybrid Electronics

06/04/2020 | Pete Starkey, I-Connect007
The emerging trend for “electronics on everything, everything with electronics” was the theme of iNEMI’s webinar presentation of the highlights of its recently published Flexible Hybrid Electronics Roadmap Chapter, delivered by Girish Wable, senior engineering services manager with Jabil. Pete Starkey provides an overview.

Improving Copper Distribution in Pattern Plating Using Simulation Software

04/28/2020 | Pete Starkey, I-Connect007
Technical Editor Pete Starkey had the opportunity to sit in on a webinar presented by Robrecht Belis, manager of the surface finishing business unit at Elsyca—a Belgian company specialising in the simulation of electrochemical processes.

I-Connect007 Survey Details Concerns About Future of Industry

04/28/2020 | I-Connect007 Research Team
I-Connect007 continues to monitor the current worldwide economic situation by seeking input from our market leaders. Here’s what we discovered: If you’re feeling the pressure, you’re not alone. In a recent survey, we asked about your primary concerns for the future of our industry. The number one concern (26%) indicated a belief that sales will be affected negatively in the coming months.



Copyright © 2020 I-Connect007. All rights reserved.