There are two major classifications for printed circuit boards or PCB, which mainly depends on their substrates. These two classifications are the flexible and rigid printed circuit boards. In this article, the focus is on the flexible PCB.
A flexible PCB assembly is composed of a flexible laminate. The qualities and the raw materials of the laminate to be used are vital not just to the production procedure, but also to the overall functionality of the completed product. The flexible laminate is made up of copper foil and dielectric substrates.
The dielectric materials are classified into two kinds, which are utilized for flexible PCB:
1. Thermoplastics – After solidification, these materials will soften by means of heat stimulant, like polyester, polymers, fluorinated hydrocarbon, and so on.
2. Thermosetting Plastics – Examples of these materials include polyimide, polyacrylate, and many others.
How to choose a specific film depends on these factors:
- Flexible PCB assembly made from polyester films which render efficiency at a cheaper price, but with a decrease on the level of thermal resistance.
- Ultra High performance flexible PCB, particularly those intended for military purposes, are produced with polyimide films since they provide the finest functionality.
- Aramid non-woven fiber is inexpensive and carries a great electrical and mechanical attribute. This material, though, easily absorbs moisture.
- Fluorocarbon, is a high priced material and quite challenging to deal with.
This, however, provides the greatest dielectric qualities. This is largely used for controlling electrical resistance purposes.
Why is a flexible PCB needed?
The earlier versions of printed circuit boards were mainly rigid. However, in this contemporary period where technology has advanced significantly, the majority of people have already been crawling towards scaled-down objects. It is for this same reason that manufacturers of PCB felt the need to make their circuit board lightweight, slim, small, and densely wired. Flexible type of printed circuit boards had come to exist to resolve these needs and requirements. These are PCB that could be wired in a 3 dimensional manner and could be adjusted to fit into the available area.
How to make Flexible PCB assembly
- Acquire thin polyimide sheets which are plated with on the two sides.
- Cut the polyimide sheet into the necessary size. Make certain that the copper does not have any spot or smudge. The edges should not be bumpy or irregular as it could damage the printer in the future.
- Get a solid ink printing device which is able to print using melted wax. Wax produces a coating on the copper, which subsequently serves as its shield while etching.
- With the use of the CAD (Computer Aided Design) software, users can now draw the circuit diagram.
- Utilize the printing device to print out this diagram on the polyimide sheet material. The printed parts are going to show up as copper tracks. Make use of dark colors that can be quickly distinguished like magenta or black.
- Let this printed sheet be soaked in ferric chloride. This is called the etching stage. This is where ferric chloride becomes a copper etchant. The process may require around 30 minutes for the copper remnants to melt and for the polyimide to appear.
- By this time, the circuit can already be installed. If necessary, cut it into smaller circuits or use it as is. Using lasers, drill some holes to be able to attach electronic parts. The circuit is currently prepared to solder.
Flex PCB assembly is easy to create and adaptable to use. However, complex equipment calls for first class printed circuit boards that can hold together for an extended period. The correct materials, correct drill, and technical know-how make a huge difference. For that reason, entrust the task solely to a specialist.