Our companies get a lot of inquiries from our customers regarding the conversion or up-gradation of a current design from its rigid printed current boards’ present configuration interconnected with a wire harness to a rigid-flex printed circuit board. With our vast experience, we can determine rapidly if a conversion option needs further investigation.
There are several reasons why a conversion needs to be investigated to determine the best solution for a specified design finally. Generally, a flex circuit board can always be used with certain exceptions. The exceptions are usually where a flex-based solution does not enhance the design but just increases the cost.
For current designs, converting from wiring to flex circuit for the majority of the cases will need a redesigning of the rigid printed circuit boards for incorporating the flex circuit. Rarely, where headers are used presently, a connector might be available for the flex circuit, letting a direct plugin replacement take place.
Why Should A Design Be Converted?
The three primary reasons seen by experts for converting a printed circuit board design are given below
Decreasing costs
Design enhancement/ requirements:
- Reliability
- Ease of assembly
- Decreased packaging size
- Functionality
For some of the applications, the justification of a flex circuit conversion can be exclusively done through a reduction in costs which can be attained. Usually, these designs have a high number of interconnects between rigid printed circuit boards, which leads to awkward and difficult wiring harnesses.
These harnesses should be hand-assembled and then their attachment needs to be done to the rigid circuit boards. This can be done by using connectors, which cover a lot of space and are bulky or soldered directly to the printed circuit boards. In either case, there is a large amount of manual assembling needed.
Conversion to a flex-based solution eliminates either any additional manual assembly or makes it a quick flex and straightforward plugin circuit operation. An essential factor in making this cost-based conversion decision is summing up “all” the costs of the wired solution.
In the majority of the cases, comparison between the costs of material will generally favor the wired solution, but once the inclusion of assembly labor costs is done the flex-based solutions lead to a reduction in costs. A lesser advantage is simplifying the designing materials’ bill.
Deciding to do the conversion for design enhancements or requirement reasons is involved more as there are design elements now which should be reviewed and addressed beyond design cost alone. In several cases, a design begins as a wired solution for proving the concept.
Once attained, extra design elements should be resolved, indicating that a wired solution might not be the optimum solution. Some of those requirements are given below
- Packaging: Wiring would not fit or fit the needed packaging size easily
- Performance: wires do not meet the electromagnetic interference needs or controlled impedance
- Reliability: Additional points of interconnect and wired solution’s mass affects reliability negatively
A flex-based solution meets the above requirements easily. Flex-based circuits approximately consume ten percent of the wiring space. They have much tighter bending abilities.
In addition to that, they meet all electromagnetic interference needs shielding/impedance needs, enhance reliability by decreasing the number of interconnect points (possible failure points) and decrease mass by up to eighty percent for vibration and shock needs.
Common flex-based options
Three of the widespread flex-based options available for inquiry in their cost structure order are given below
- Rigid printed circuit boards and flex circuit
- Stiffeners and Flex
- Rigid-Flex
- Which of the above options is best depends upon the various variables given below?
- Current rigid circuit board design’s layer count
- Connector types needed
- Shape and size of the complete unit
- Performance needs, impedance, current and electromagnetic interference, current, etc
- Number of interconnects
All solutions have their own strengths and capabilities. Flex circuit technology has an extensive range of available configurations, which creates a very capable interconnect solution.
The rigid printed circuit board and flex-based circuit
This is a practical solution for several applications. Out of the two methods, it is usually the more cost-efficient. The rigid printed circuit boards’ cost remains as it is, which is lower than that of rigid-flex or flex. Then, the flex circuit board as a whole part is connected to the rigid printed circuit board. There are various connectors available depending upon your precise design needs.
The most popular and standard flex connector is ZIF connectors. Their benefit is that they are a cost-efficient one-part connector system that can survive without requiring any connector assembly on the flex circuit.
The flex circuit directly plugs into the ZIF connector. ZIF connectors are available for extensive applications, i.e., mechanical retention tabs, electromagnetic interference shielding, and controlled impedance for highly reliable applications.
Other than ZIF connectors, the attachment of any other connectors which can be soldered to a right printed circuit board can be done to a flex circuit. A disadvantage of this method is that ZIF connectors consume the rigid printed circuit boards. Usually, the flex circuit is limited to three or fewer circuitry layers.
Rigid-Flex Circuit Board
The rigid-flex circuit board option is integrated fully where the lamination of flex layers is done inside rigid areas. No extra connectors are needed. This method is competent but is very expensive. Rigid printed circuit board real estate is freed up, possibly permitting a lesser rigid area. The availability of higher flex layers permits a large number of interconnects between rigid parts.
Electromagnetic interference and controlled impedance needed are met easily. Surface mount technology components can be installed on rigid areas’ both sides. Typically, this solution is applied beforehand that the wired proof of concept will not fulfill the final assembly’s packing requirements.
Summary
How to convert the current design to the flex-based circuit design is a question commonly asked by the customers of Shenzhen Haoda Electronics Technology Co. In most cases, its customers lack the knowledge required to do decision-making regarding such a conversion.
