Certain factors or parameters are worth putting into perspective to help the decision-makers decide on the best way to go about something. In terms of circuit board design, you want to take into account the Bill of Materials, the schematics for the board and the deliverables.
Read this article to the end to find out in details, the most important factors to consider before you make a Printed Circuit Board (PCB).
1. Consider the Schematic Details
Schematics are the different elements that come together to bolster the functionality of the PCB. These elements work along the lines of routing and making the layouts of the circuit board.
The following are some of the special requirements making up the layout notes required to make the net items:
- High frequency
- High current
- High voltage
- The minimum and the maximum spacing
- Controlled impedance
- Star grounds
- Differential pairs
- The sensitive analog circuits
2. Circuit Stacking Method
This refers to the method of stacking the layers of the Printed Circuit Board (PCB). It also involves the desired levels or height to which the PCB is expected to attain.
Determining the accurate stackup is a major way to determine the types of materials needed for the job. This will, in turn, influence what you will have in the Bill of Material (BOM).
3. Bill of Materials
This is a “bill” dedicated to highlighting the different components or materials required for the printable PCB design.
Certain parameters worth considering when drawing up the BOM include:
- Component List: this refers to the parts or components needed for the circuit board design. To simplify the process, it is important to add extra details, such as the source or part number of the PCB.
- Cross-Referencing: is there any need to cross-reference the components/parts in the BOM? If so, specify if cross-referencing is allowed.
- Datasheet: do you have access to some of the datasheets for these components? If so, you can provide those to help the PCB printer to spend less time researching about them.
- Component Quantity: this refers to the number or quantity of the components needed for the printable PCB design.
4. Vias Selections
Vias refers to the connections used between the several layers in a PCB. There are a wide range of options to choose from. Such options are micro, through-hole, buried and blind vias.
Note that the vias selection is directly correspondent to the type of PCB and its thickness. You can choose between a mono (one) to a multilayered PCB, based on the thickness.
5. Printable PCB Design & Layout Format
This refers to the format or process of making the layouts and diagram of the Printed Circuit Board (PCB). For the best results, you want to choose from any of the different software options out there. It is also possible to submit an image file.
The following are important considerations for a printable PCB, based on the design and support format:
- Software: the type of circuit board software used is important. Although the functionalities differ from the software, the basics should be extensively harnessed. The software helps in the making of initial designs of the circuit board.
- Signal Integrity: what is the quality of the signals transmitted and how reliable are they? The following factors tend to influence the quality of the printable PCB’s signal: drive strength, the rise and fall times of the signal, the length of the tracks and impedances.
6. Thickness Measurement
The thickness of the PCB impacts the selection of vias, which will be used to connect the layers. To that end, you must make an accurate measurement of the thickness.
Here are some of the things you need to know about the process:
- Measurement Procedure: it is common to use ouncers of copper to measure how thick a printable PCB. You can use between an ounce or two ounces of copper for the measurement. However, it is also possible to increase the ounces to 6, if you are looking to get higher thickness values.
- Board Requirements: just as you are measuring the thickness, make sure to balance that with the printable circuit board’s requirements. The reason is that if the wrong trace thickness is used for the design, it triggers both soldering and laminating issues.
7. Design Rules
These are the dedicated guidelines on how to make the circuit board. Your printable PCB manufacturer requires this before working on the board, as it serves as a guide to designing circuit boards that match your requirements.
The following are some of the important pieces of information to provide for the design rules:
- Lead Time: this refers to the length of time or how long it is expected for the engineering and manufacturing of the printable PCB should take. Some of the factors that could decide the potential lead time are the numbers of circuit boards to be printed and the strenuous design of the entire process.
- Component Positioning: make sure to include the positionings or where the parts/components are to be placed or mounted on the PCB’s surface.
- Layering: this has to do with the layer allocation – how many layers are to be used and where are they to be used?
- It is also important to include an analysis of the time of flight.
8. Manufacturer’s Deliverables
These are the items the manufacturer expects of you to provide before the designs start. The most popular deliverable is the Gerber file.
The following are some of the additional items to provide when requesting a quotation for your printable PCB design:
- PCB Diagram: this is a construction or construction drawing of the circuit board.
- The Gerber files. It is common to have this submitted in the RS274X format.
- BOM: the Bill of Materials (BOM) must be submitted, as it includes the different parts required for the design. You can submit it in different file formats, including Comma Separated Value (CSV) text file.
- Positive layers
- A pick and place file should be provided for the bottom and top layers of the printable PCB.
- You should also provide the drill tool and drill job files.
Steps to Making Your Printable PCBs
You can now make your Printed Circuit Boards (PCBs) on your own. This DIY process shows you how to get started.
1. Gather the Tools and Materials
The tools you need range from eye protection, mini drill, latex gloves and flat iron. You also need either a photocopying machine or laser printer.
For the materials, you need glossy paper or magazine paper, an etching solution, a small piece of cloth and the PCB board. You also need a sanding paper, a fine tipped marker, plastic straws/plastic tweezers and a ruler (this is optional).
2. Make the PCB Layout
The layout is a diagram of the Printed Circuit Board (PCB). It forms the main board’s configuration, as it has to do with turning the schematic into the PCB software for designing.
3. Print the PCB Layout
After the schematic has been turned into the software and the design made, you can then print it out. This is where you need the photocopying machine or the laser printer.
A couple of considerations should be held higher when doing this. They include:
- Use either magazine papers or a glossy paper. They provide to hold the ink, unlike using them with the water-soluble Inkjet Printers that make the ink transfer to the PCB impossible.
- Make sure that the printing is done on the magnificent side of the glossy paper.
4. Transfer the Ink & Cut the Copper Plate
The ink can be transferred faster to the PCB by using the flat iron to press it onto the circuit board. The temperature of the iron also makes the process faster – you can use the highest temperature if you are working with a thick, glossy paper.
Once that is done, you can then start the copper plating process, by cutting the copper board to the right size.
5. Smoothen the Surface
Due to the copper plate cutting size, it is possible for the edges to be rough. It is therefore expedient to smoothen the surface. This can be done via using a sharp brush to scrub the copper side of the circuit board until it smoothens.
You can also use the sanding paper to smoothen the board’s edges so has a finer finish.
6. Restore the PCB
Circuit board restoration, in this case, refers to the process of fixing some of the issues that may arise after the surface has been smoothened. Ideally, you will notice that some of the inked areas on the PCB might have been removed, in the process of sawing or smoothening out the rough edges.
If that is the case, as it usually is, you have to restore the PCB by using a ruler and the tipped marker to restore those areas.
7. Etch the PCB
Etching a PCB refers to the processes involved in removing the undesirable copper from the circuit board. To actualize this process, an etching solution, usually Ferric Chloride is to be used.
The procedures to etching a chip/PCB include:
- Pour the etching solution (Ferric Chloride) into the plastic container.
- You can dip the PCB board into the solution and allow it to sit there for up to 45 minutes.
- During the etching process (while the PCB board is sitting in the etching solution), the solution will be interacting with copper unmasked. At the same time, it eliminates or removes the undesirable copper from the PCB board.
- Note that allowing the board to sit in the board for a longer time might expose it to getting rid of some of the inked areas. Therefore, any time between 30 and 45 minutes maximum is sufficient for the etching process to be completed.
- However, if on removal from the etching solution and you discover some undesirable copper still left behind, you can consider putting the board back into the solution until the copper is fully removed.
- The best way to remove the board from the solution is by using either the plastic tweezers or plastic straws. You must not make a direct contact with the board either. You must put on latex gloves before getting into contact with the solution and when cleaning the PCB board.
8. Thorough Board Cleaning
The PCB board must be thoroughly cleaned. The process includes using a laundry soap to brush the remaining inked areas on the board.
This process exposes the board’s copper areas and helps you see if they are well-aligned.
9. Hole Drilling
Drilling holes on the printable PCB makes a lot of sense if you are working on a multilayer board. Drilling holes can be done with the mini drill.
Make sure to rinse the circuit board after drilling the holes. Note also that the drilling must also be on the side where the copper is inserted on the PCB.
10. Solder the Components
The drilling of the holes is meant to create a pathway for the inserting the components or leads through the holes. You can now solder these leads through the holes you drilled on the PCB.
Comparing Traditional Printable PCB with 3D Print PCB
These are two (2) different ways to make prints of circuit boards. Unlike the traditional PCB designs that deal with diagram transfer of the designs, the 3D print PCB has to do with the making of a three-dimensional (3D) design of the board.
To further compare the two, here are some of the differences between traditional circuit board printing and 3D PCB printing:
- Traditional circuit board printing uses either a photocopying machine or a laser printer while the 3D printing format uses the Inkjet Printer.
- Three-dimensional (3D) PCB printing is economical, in the sense that generates less waste material and minimizes the errors, unlike the traditional PCB printing process.
- While the traditional PCB printing method involves the etching of the copper tracks on the substrate, the 3D printing method doesn’t support that.
Conclusion
Finally, you need to learn how to make a PCB, as well as the different processes that go into it. A professional printable PCB manufacturer will help transfer the ideas you have into a finished Printed Circuit Board (PCB), specially designed for the desired applications.
