WHAT IS PCB FABRICATION PROCESS?
Introduction
What is PCB Fabrication？
PCB fabrication, also known as PCB manufacturing or PCB production. It is the process of creating printed circuit boards (PCBs) used in electronic devices. PCBs are thin, flat boards made of insulating materials such as fiberglass or plastic. with conductive pathways etched onto their surface to allow for the flow of electrical currents.
The fabrication of a PCB is a complex process. that begins with the product concept and finishes with the assembly of a functional PCB. PCB design lays out physical circuits. and schematics order electrical components to capture network connections. After soldering and testing, the board is integrated into the system.
STEP BY STEP PCB FABRICATION PROCESS
The PCB fabrication processing involves several steps, including：
- Designing the circuit layout;
- Choosing the appropriate materials;
- Printing the circuit onto the PCB substrate;
- Drilling holes for components and vias;
- Applying a protective layer;
- Testing the finished product;
1. Designing The Circuit Layout
Circuit layout design optimizes performance, reliability, and manufacturability. Here are some general steps to follow when designing a circuit layout:
Start with a schematic:
Understand the circuit’s functionality before constructing a physical architecture. Draw a schematic that includes all of the components and their connections. This will serve as the foundation for the layout.
Determine the size and shape of the board:
Consider the size of the components and the amount of space required for the circuit to function . You’ll also need to determine the shape of the board, including any cutouts or mounting holes.
Place the components:
Using the schematic as a guide, place the components on the board. Consider factors such as component size, thermal considerations, and signal routing.
Route the connections:
Once the components are in place, you’ll need to route the connections between them. This involves creating a network of traces that carry signals and power throughout the board. Consider the length and width of the traces, as well as their proximity to other traces and components.
Add power and ground planes:
To ensure reliable operation, it’s important to create dedicated power and ground planes on the board. These planes provide a low-impedance path for current flow. and help to reduce noise and interference.
Verify the design:
Once the layout is complete, use design rule checks and other verification tools. to ensure that the board meets all necessary specifications. This includes checking for proper clearance, signal integrity, and manufacturability.
Generate manufacturing files:
When the design has finalized, generate the necessary manufacturing files. including the Gerber files, BOM, and assembly drawings. These files used to create the physical board.
2. Choosing The Appropriate Materials
Choosing the appropriate materials for PCB fabrication is important. That to ensure that the board meets its intended specifications and functions . Here are some factors to consider when selecting PCB materials:
Substrate Material:
The substrate material is the core component of the PCB. and provides mechanical support for the copper layers. The most common substrate materials are FR-4 (fiberglass epoxy), polyimide, and Rogers. FR-4 is the most widely used material and is suitable for most applications. while polyimide and Rogers used for more specialized applications. that require high-temperature resistance, flexibility, or high-frequency performance.
Copper Foil Thickness:
As we konw, copper foil laminated to the substrate material and used to create the traces and pads on the PCB. Copper foil thickness typically ranges from 0.5 oz to 6 oz, with 1 oz being the most common. Thicker copper foil provides better current carrying capacity. but also increases the cost of the PCB.
Solder Mask:
Solder mask is a layer of polymer that applied to the PCB to protect the copper traces. and pads from oxidation and to prevent solder from bridging between adjacent pads. The most common solder mask colors are green, blue, black, and white. but other colors are also available.
Surface Finish:
The surface finish is the final coating that applied to the copper traces. and pads to protect them from oxidation and to provide a surface for soldering. Common surface finishes include HASL, ENIG and OSP .
Other considerations:
Other factors to consider when selecting PCB materials include the operating temperature range. the dielectric constant and loss tangent of the substrate material. and the type and thickness of the plating used for the holes.
3. Printing The Circuit Onto The PCB Substrate
Align and expose the artwork:
The PCB artwork placed on top of the coated substrate material. and aligned to ensure accurate transfer of the circuit design. The artwork is then exposed to UV light. which causes the photoresist material to harden. and adhere to the substrate material in the areas not covered by the artwork.
Develop the photoresist:
The coated substrate material developed using a chemical solution. that removes the photoresist material from the areas that were not exposed to light. This exposes the copper layer in those areas and prepares the substrate for etching.
Etch the copper layer:
The exposed copper layer etched using a chemical solution. that removes the unwanted copper. leaving only the traces and pads that make up the circuit design.
Remove the photoresist:
The remaining photoresist material removed using a chemical solution. leaving the completed circuit design on the substrate material.
Add the solder mask and surface finish:
The completed PCB coated with a layer of solder mask material. and the surface finish applied to the exposed copper areas. to protect them from oxidation and provide a surface for soldering.
4. Drilling Holes For Components & Vias
Drilling holes for components and vias in a PCB
That involves creating precise holes in the substrate material . to fit the leads of the components or to link different layers of the board. Here are the general steps involved in the drilling process:
Prepare the drill files:
The PCB design software should include drill files. that specify the location, size, and type of each hole that needs to drilled. These files are typically in the Excellon format.
Choose the appropriate drill bit:
The size of the drill bit used will depend on the size of the holes and the required accuracy. Standard drill bits range in size from 0.2mm to 6mm. Carbide drill bits are commonly used for drilling PCBs. because they are durable and can maintain their sharpness over time.
Set up the drilling machine:
The drilling machine programmed to drill the holes according to the drill files. The machine will need to calibrated to ensure that the holes drilled and to the correct depth.
Load the PCBs:
The PCBs loaded into the drilling machine. on a vacuum table or clamping mechanism, to hold them in place during the drilling process.
Begin drilling:
The drilling machine is activated. and the drill bit lowered onto the substrate material to create the holes. The machine will move the drill bit to each hole location. specified in the drill files and drill the holes to the required depth.
Inspect the holes:
Once the drilling process is complete. the PCBs inspected to ensure that all of the holes have drilled to the correct size, location, and depth. Any errors or defects identified and corrected . before proceeding to the next step in the fabrication process.
5. Applying a Protective Layer
After drilling the holes and placing the components. the final step in PCB fabrication is to apply a protective layer. to ensure the reliability and durability of the board. There are several types of protective layers that applied to a PCB. including conformal coating, solder mask, and silkscreen.
Conformal Coating:
This is a thin, protective layer that applied to the surface of the PCB. to protect it from environmental factors such as moisture, dust, and temperature fluctuations. The coating material can be silicone, acrylic, or polyurethane. and it applied using methods such as spraying, dipping, or brushing.
Solder Mask:
This is a layer of polymer that applied to the surface of the PCB. to protect the copper traces from oxidation. and to prevent solder bridges from forming between adjacent pads. The solder mask applied using screen printing, spray coating, or curtain coating methods.
Silkscreen:
This is a layer of ink that printed on the surface of the PCB. to identify the components and to provide more information. such as logos, part numbers, and warning labels. The silkscreen applied using screen printing or inkjet printing methods.
6. Testing the finished product
Before applying any components or protective layers to a PCB. it is important to test the bare board . to ensure that it meets the required specifications . and that there are no defects or errors in the manufacturing process. Here are some common methods used for testing a bare PCB board:
Visual Inspection:
A visual inspection is the first step in testing a bare PCB board. The board inspected for any visible defects. such as scratches, cracks, or incorrect markings.
Electrical Testing:
Electrical testing involves using a tester to measure the conductivity of the copper traces. and to verify that there are no short circuits or open circuits on the board. This is typically done using a multimeter or a dedicated PCB tester.
Impedance Testing:
Impedance testing used to measure the impedance of the traces on the board. and to ensure that they meet the required specifications. This is particularly important for high-speed and high-frequency applications.
X-ray Inspection:
X-ray inspection used to detect defects or errors. that may not be visiblePCB Fabrication Capabilities to the naked eye, such as voids in the solder joints or hidden shorts.
Functionality Testing:
Functionality testing involves connecting the bare PCB board to a test fixture. or a prototype device and verifying that it performs as expected.
CONSIDERATIONS FOR THE PCB FABRICATION PROCESS
PCB fabrication is a detailed process. and even minor errors can cost businesses money due to faulty construction. Consider using PCB fabricators with a track record of success. when selecting your PCB fabrication company. GESP TECHNOLOGY manufactures aerospace-quality PCBs . and is capable of handling both the fabrication and assembly processes. Our credentials include the following: Our qualifications include:
- Turnaround in as little as 24 hours
- High mix low-to-mid volume
- Class II and Class III inspection
- Leaded and lead-free RoHS assembly
- 100% on-time guarantee
- Design services (Outsourced)
- Full box build
If you’re looking for the best quality PCB fabrication company. look no further than GESP TECHNOLOGY. Our pricing is competitive, and our speed can’t be beat. Get a quote for PCB fabrication now.