Printed Circuit boards are significant components of most, if not all, electronic and electrical components. These components dominate the electronic and electrical industry due to their ability to help manufacturers generate compact gadgets that are powerful and efficient. Moreover, due to their compact size, they make the packaging process easier and more effective.
However, out of the many different types of PCBs that exist, flexible PCB top the list in terms of printed circuit boards that offer impeccable space efficiency. Due to their ability to curve into various shapes, manufacturers utilize them to make pretty tiny gadgets such as hand-held gadgets and wearables. However, even though flex PCBs are efficient, their production process can be rather complex due to the flexibility of the components that technicians utilize to make these circuit boards. However, did you know that with the proper guidance, you can make a flexible PCB at home? Here are some instructions to help you generate your flexible PCB in the comfort of your home.
What is a Flexible Printed Circuit Board?
Before we move on to how you can generate a flexible printed circuit board at home, let us first look at what a flex PCB entails.
Generally, flex PCBs feature a combo of different types of PCBs and various flexible materials. Therefore, these popular printed circuit boards go by multiple names, which include flexible circuit boards, flex circuits, flex PCBs, and flex circuit boards. Moreover, technicians utilize the same elements that they utilize to make rigid circuit boards to generate flexible PCBs, only that the elements they use in flexible PCBs are flexible, which results in a flexible PCB.
Types of Flex PCBs
Flex PCBs come in many variations due to various specifications and configurations that technicians make during production. However, when it comes to classification, we classify them according to their configurations and layers as follows:
Flex PCBs as Per Configuration
When it comes to classification via configuration, you can group flex PCBs as follows:
HDI Flex Printed Circuit Boards
HDI (high-density interconnect) printed circuit boards are flex PCBs that cater to applications that require high-performing flex printed circuit boards. Due to their build, they tend to have impeccable performance compared to other circuit board types.
The design of an HDI flex printed circuit board incorporates several features, including micro-vias. Moreover, these circuit boards provide better construction, designs, and layouts.
Generally, these circuit boards use thinner substrates when compared to regular flex-printed circuit boards. Due to these features, these flex PCBs help manufacturers reduce costs in terms of procuring raw materials. Moreover, they also end up having reduced package sizes which helps during shipment and application in generally smaller gadgets.
Rigid Flexible Printed Circuit Boards
Rigid flexible printed circuit boards are typically hybrid printed circuit board that combine the features of a rigid and a flexible printed circuit board.
These variation of flexible printed circuit boards is pretty popular since it bring the best features of both worlds.
Classification of Flex PCBs Using Layers
The classification of flex PCBs using layers groups the various flexible PCB types into the following categories:
Single sided flex Printed Circuit Boards
The single-sided flex PCB is basically among the most basic variation of flex PCBs. That is because this flex PCB variation only has one layer of flex polyimide film and a slim layer of CU (copper). Moreover, the conductive layer is only accessible via the top part of the circuit board.
Single Sided Flex PCBs with Dual Access
Single-sided flex PCBs with dual access are simply single-sided flex circuit boards that are designed such that you can access the conductive layer via both sides of the board.
Double-sided Flex PCBs
Double-sided flex PCBs typically feature two copper conductive layers, which technicians place on either side of the polyimide or substrate layer. To make electrical connections between two copper conductive layers, technicians utilize a method known as THT (through hole).
Multi-Layer Flex PCBs
Multi-layer flexible PCBs are generally a combo of multiple single-sided and double-sided flex circuit boards. To make interconnections within these circuits, technicians utilize various technologies, which include:
- Surface mount technology or SMT
- Through-hole technology or THT
Main Benefits of Working with Flex PCBs
Over time, flex PCBs have become pretty popular due to their multiple benefits. Here are some of the most common benefits of flex printed circuit board:
Reduce Package Size
Generally, flex PCB can easily fit into multiple applications where other PCB types might not work efficiently or at all. That is because these circuit boards are typically lightweight and thin. Moreover, you can easily fold, crease and position these circuit boards in various areas that are space deficient. Moreover, due to their slim size, they end up generating a small package that is easy to ship.
Accurate Designs
Manufacturers primarily utilize automated machinery to effectively assemble and design printed circuit boards. The utilization of these gadgets helps in terms of reducing errors that tend to occur due to harnesses and hand-built cables. Moreover, these gadgets ensure impeccable accuracy, which is crucial when dealing with printed circuit boards.
Design Freedom
The designing process of PCB isn’t limited to merely two layers. Due to their flexibility, these circuit boards provide PCB designers with a lot of freedom when it comes to designing them. Moreover, PCB designers can choose to either go with single-sided flex PCBs, double-sided flex PCB, or multi-layer flex PCBs when generating their designs.
The flexibility that comes with flex PCBs also makes them perfect for applications that require multiple interconnections with complex configurations. Moreover, you can design your flex PCB to cater to both SMT components and THT components.
High-Density Config
Flex-printed circuit boards can encompass a mix of surface mount and thru-hole components. By utilizing this feature, you can easily generate a flex PCB that can accommodate high-density gadgets with narrow separation within the layers. Moreover, you can also design lighter and denser conductors, freeing up space to accommodate additional components.
Flexibility
Flex PCBs can easily connect with various planes when operational. Doing so helps in terms of reducing space and weight issues that most people face when working with rigid printed circuit boards.
Steps to Generate a Flexible PCB at Home
If you are looking to generate a flexible printed circuit board at home, here are the steps to follow:
Get a Copper Coated Film
To start off, you’ll need to purchase a thin sheet of polyimide bearing copper on either both sides or simply one side depending on the type of flex PCB you want to generate. Typically, polyimide sheets are yellow, and they have high melting points. Moreover, people sometimes refer to this component as Kapton. Furthermore, copper-coated polyimide tends to come in many variations, but the most common type is DuPont material.
DuPont sheets also generally come in different variations due to varying copper thicknesses, adhesive thicknesses, and polyimide thicknesses in general. CU or copper thickness is usually given in mils, where one mil is typically equal to 0.001 inches.
For this project, you can utilize a Dupont LF7062, which has 0.5 mils of adhesive, 0.5 oz of copper, and about one mil of Kapton. However, you can still go for more variations since this type of film tends to be crinkly and a bit thin. For instance, you can go for the Dupot LF9210, which contains one mil of Kapton, one mil of adhesive, and 2 oz of copper.
Other variations include double-sided CU with rough surfaces. These variations are typically denoted by the letter R.
After obtaining the sheet, you have to cut it to fit the following dimensions:
- 8.5 by 14 inches
- 8.5 by 11 inches
Do not smudge the copper using oil or fingerprints during the cutting process. Doing so can easily block the etching solution later on. Moreover, to shield the printer from damage, try to flatten the sheet’s edges.
Utilize a Solid-Ink Printer
To print directly onto the CU film, you must work with a solid-ink printer. These printers look pretty similar to laser printers. However, they usually utilize melted wax to print rather than ink. Moreover, the wax that this printer utilizes to print makes a perfect shielding layer for CU (copper) etching. And unlike most laser printers, this printer does not rely on charging the paper’s surface since this could lead to issues when you change the paper and replace it with copper sheets.
Here are some solid-ink printer models that you can find in the market:
- Xerox Phaser 8860, 8560, 8500, 8400 and 8200
- Tektronix Phaser 860, 850 and 840
Most Phaser solid-ink printers also function like regular laser printers. However, they do have a hood that contains a solid ink block.
If you can’t access a solid ink printer, you can use the toner transfer method, which utilizes laser printers.
Print your Design on the Pyralux
Once you have your solid ink printer up and running, it is time to print your design on the copper film. To do so, you must first draw the design using a graphics program like CAD. Once the design is ready, you can utilize the manual feeding tray to effectively print the design onto your copper sheet in black. You can also utilize various color variations, which include:
- Yellow
- Magenta
- Cyan
- Green
- Red
However, you should avoid colors that have light shades. These colors will not bring out your design clearly on the board.
During the printing process, you should utilize photo or high-resolution mode, which is usually available in the setup area of your graphics program. Generally, the high-resolution mode tends to print in a slow manner when compared to the standard printing mode. However, it is more efficient and promotes impeccable adhesion of the wax to the copper.
Most phaser printers usually print the copper sheet with the copper side facing down. However, when it emerges at the other end, it does so with the copper sheet in an upside-down position.
If the printer’s feed cog faces some issues grabbing the sheet, you can give it a slight shove to help it out. However, it would help if you were gentle to avoid damaging the copper sheet.
Etch your Copper Sheet
Once you are done with the printing step, you then have to insert the copper sheet inside the ferric chloride for about 5 minutes. When using the etchant, avoid getting the chemical on your skin or eyes.
The etching time typically depends on various conditions, which include:
- The thickness of the copper
- The temperature and more
Due to these variations, you should keep checking on the board when it is inside the etchant to ensure that the polyimide film shows up in the necessary areas. The etching process can sometimes take over 25 minutes, depending on the conditions specified above.
Utilizing an aquarium pump to bubble the solution and heating up the solution to around 400C can help you speed up the etching processes and gain a more evenly etched printed circuit board.
Populate your Flex Printed Circuit Board
Once you are done with the etching process, your flex-printed circuit board is now ready for the next phase. For the next part, you can choose to cut the circuit board into small circuits, then solder your components, or you can simply solder components onto the circuit board without cutting the board at all. It all depends on how you are looking to utilize your printed circuit board.
When working on your flex printed circuit board, you can attach it to a fiberglass PCB or a metal block to keep it steady during placement.
You can utilize a nickel plating solution to make the soldering process easier. However, freshly cleaned and etched flexible printed circuit boards tend to be easily solderable without adding more solutions.
Since the flex-printed circuit board in this article is one-sided, without holes, you can utilize it as a PCB for SMT parts or as a simple cable. In addition, you can use jumpers for traces if you deem it necessary.
Conclusion
Flexible printed circuit boards are pretty efficient due to their flexibility. Using these circuit boards, you can easily generate pretty powerful compact gadgets that function impeccably. However, the production processes of flex printed circuit boards can be tricky due to their flexibility. But using the proper guidance and the right tools, you can quickly achieve functional, flexible printed circuit boards without breaking a sweat. Therefore we hope this article will help you generate a practical, flexible printed circuit board at home.
