mobile | classic
Dataweek Electronics & Communications Technology Magazine

Follow us on:
Follow us on Facebook Share via Twitter Share via LinkedIn


Electronics Buyers' Guide

Electronics Manufacturing & Production Handbook 2019


Eight things to consider when planning a flex or rigid-flex board
EMP 2019 Electronics Manufacturing & Production Handbook, Manufacturing / Production Technology, Hardware & Services

Every day you can read about the Internet of Things (IoT), API, Industry 4.0 and automation in the news. The future is not something seen in movies (like we did back in the eighties when Back to the Future seemed like Utopia) – we know better. The future is now, and all the new products and possibilities it brings will certainly change how we design printed circuit boards (PCB).

Within this context, it is no surprise that there is a trend towards increasing demand in flex and rigid-flex PCBs. The demand for flex and rigid-flex circuits naturally increases when new and advanced technology requires it. The competitive situation also forces companies to bring these new products to market at an ever-increasing rate.

Many products connected to the IoT and flexible displays demand smaller, lighter and more cost-effective products. In these cases the flexible circuit is a viable option. Flexible PCB material is utilised to meet challenging form-factor requirements, eliminate connectors and improve performance.

One positive aspect with flex and rigid-flex circuits is the reduction in assembly time. For rigid-flex, reduced use or elimination of connectors will also increase reliability. Customers often request a reduction in costs, time spent in assembly, fewer cables and sockets. These requirements are in many cases solved with flex and rigid-flex boards.

A huge variety

The adoption of flexible circuits is growing because it offers a huge variety for seamless interconnections, lighter weight, improved reliability and compressed constructions. With the many manufacturing options and material choices available to prospective flex circuit users, the possibilities and processing choices are numerous.

So why do we talk so much about rigid-flex now? Consider the trends in the news: IoT is not just a buzzword tech-bloggers toss around, it’s a completely new industry where rigid-flex boards fit like French cheese and wine. With the rising possibilities IoT brings, it can come in handy to have some advice on what to consider when planning rigid-flex printed circuits.

The following are eight things to consider when planning a flex or rigid-flex board:

1. Weight reduction. The use of flexible circuits can reduce the weight of an electronic package significantly, due to the fact that they do not have reinforcements that are characteristically higher in density than unfilled polymers.

2. Decreased assembly time. Seamless integration of several rigid boards into one rigid-flex, which can be assembled and soldered as one PCB, will save time. Connectors and cables are gone, and reliability is another benefit borne out of this.

3. Purchasing cost. The purchasing cost might be higher when purchasing a rigid-flex PCB, where several pieces are connected together with flex, than purchasing each board separately. However, you do not need to buy any connectors or cables between them. And with the increased system reliability you get by not using connectors and cables, the benefit might outrun the cost.

4. Dynamic flexing or just a bend-and-stay solution. The very thin polyimide with a very thin copper foil is ideal for dynamic flexing applications. For a bend-and-stay application a thicker or multi-layered flex can be used.

5. Heat dissipation. Heat dissipation is normally better on the flat copper tracks you find on a flexible circuit, compared to the round wire surrounded with insulation material. This makes the flexible circuit a preferred choice in areas where resistance to heat is crucial. Stack-up for improved signal integrity is also available when using reference/shielding layers. Flexible circuits are more resistant to heat than printed circuits, such as FR4.

6. Bending radius. This depends on the number of layers to be bent, the thickness of the copper and the total thickness, and whether it is dynamic or just a few bends. Specific figures are available for this, shown in Table 1.

7. Materials. Most common materials are polyimide (PI), but there are also other materials available such as PET (polyester), PEN (polyethylene naphthalate), LCP (liquid crystal polymer) and others. Polyimide is the one used for products where reliability is a top priority.

Polyimide has the advantages of excellent flexibility at all temperatures, good electrical properties, good chemical resistance (except hot alkaline solutions), good tear resistance and high tensile strength, but suffers from high moisture absorption of up to 3%, is expensive compared to PEN, and its high-temperature performance is worse if used with an adhesive system.

Comparatively, PET polyester is low-cost and offers good flexibility and tear resistance, low moisture absorption, good electrical properties and good chemical resistance. Since it is a thermoplastic, it can also be formed. However, it is not suitable for soldering and is unsuitable for extreme cold as it becomes brittle.

8. Design possibilities. Finally, and quite simply, designers benefit from an increase in design possibilities when using flexible circuits.

For more information visit

  Share on Facebook Share via Twitter Share via LinkedIn    

Further reading:

  • Designing PCBs for Mil Spec
    29 May 2019, Cirtech Electronics, Manufacturing / Production Technology, Hardware & Services
    In the field of electronics, Mil Spec – or Military Specification – has a very clear and understood meaning. It denotes equipment designed and made to exacting standards, in accordance with precise rules ...
  • Continued success for Zetech’s stencils division
    30 April 2019, Zetech, This Week's Editor's Pick, News, Manufacturing / Production Technology, Hardware & Services
    Best known for supplying SMT (surface mount technology) equipment and consumables for printed circuit board assembly for 33 years, Zetech is enjoying success with its more recently established stencils ...
  • How to analyse blind via hole failures
    27 March 2019, This Week's Editor's Pick, Manufacturing / Production Technology, Hardware & Services
    It has become common practice to use blind, filled and stacked vias in many portable electronics products. Experience has shown that this method of interconnection is reliable, provided the fabrication process is well defined and controlled.
  • PCB microsectioning – paying attention to detail
    27 March 2019, Cirtech Electronics, This Week's Editor's Pick, Manufacturing / Production Technology, Hardware & Services
    In our high-tech world, it’s easy to overlook the importance of the humble printed circuit board (PCB). Buried in each electronic gadget or appliance there’s always at least one PCB and each one has ...
  • X-ray dose considerations
    27 March 2019, MyKay Tronics, Manufacturing / Production Technology, Hardware & Services
    The benefits of using X-ray technology in the electronics industry to inspect printed circuit board assemblies are well proven. This article summarises X-ray radiation dose, and the techniques that ...
  • Product development issues explored in new video
    27 March 2019, Manufacturing / Production Technology, Hardware & Services
    Printed circuit broker, Elmatica, recently released a new film about product development, explaining why cooperating with an experienced partner could be a smart move. “We have several times seen the ...
  • Flux management system earns APEX award
    27 March 2019, MyKay Tronics, Manufacturing / Production Technology, Hardware & Services
    BTU International was awarded a 2019 NPI award in the reflow soldering category for its new Aqua Scrub flux management technology. The award was presented to the company during a ceremony that took place ...
  • Solder dross recovery system
    27 March 2019, Electronic Industry Supplies, Manufacturing / Production Technology, Hardware & Services
    Stannol’s Solder Saver is a mechanical device to reduce dross, which occurs as an unavoidable side effect in wave soldering systems. According to its manufacturer, solder consumption can be reduced by ...
  • Water-soluble solder paste
    27 February 2019, Techmet , Manufacturing / Production Technology, Hardware & Services
    Indium has released Indium6.6HF solder paste – a new water-soluble, halogen-free solder paste that is compatible with both tin-lead and lead-free alloys. It is designed to provide enhanced stencil printing ...
  • Affordable soldering station
    27 February 2019, Electronic Industry Supplies, Manufacturing / Production Technology, Hardware & Services
    The Industa 550 soldering station, available from Stannol, is an affordable unit characterised by easy operation and universal fields of application. The temperature is easy to set using a potentiometer, ...
  • Stencil underside cleaning and manual post-cleaning
    27 February 2019, Testerion, Manufacturing / Production Technology, Hardware & Services
    According to experts, between 60 and 70% of all defects and failures during or after the soldering process are attributable to defects in the printing process (Figure 1). In general, these are faulty ...
  • What you need to know about the Hermes standard
    EMP 2019 Electronics Manufacturing & Production Handbook, Manufacturing / Production Technology, Hardware & Services
    Taking advantage of modern TCP/IP communication and XML data format technologies, Hermes is effectively a replacement of the more than 20-year-old SMEMA standard.

Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronics Buyers’ Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Terms & conditions of use, including privacy policy
PAIA Manual


    Classic | Mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.