A double layer pcb board provides greater circuit integrity by limiting signal lengths. Longer traces cause parasitic resistance and capacitance which can degrade signal quality through interference coupling from adjacent signals.
With a second copper layer, engineers have increased flexibility when positioning ICs and placing components. This enhanced layout versatility unlocks more complex architectures for prototyping designs.
Top Layer
The top layer of a double-layered PCB is used for routing signals to and from the bottom layer. It is also useful for adding shielding to sensitive signal traces and for distributing power to components. These benefits, coupled with their compact size and low weight, make double-layer circuit boards a popular choice for industrial control systems and power supplies.
The first step in designing a double-layer PCB is to accurately capture the schematic. This is essential for proper layout design and will ensure that the board complies with all electrical and physical requirements. This requires Tetris-like precision, and a good CAD system, like Eagle or CircuitMaker, will assist in capturing accurate symbols and connectivity.
Once the schematic is captured, the layout design begins. This is where the complexities of a double-layer PCB come into play. The layout must take into account:
Using the schematic, the LAYER1 mechanical layer is designed. This includes the mechanical dimensions, data marks, assembly instructions and other mechanical information. The etching solution is then mixed according to the manufacturer’s instructions. It is important to follow all safety precautions, including the double layer pcb board use of gloves, eye protection, a gas mask or respirator and full-sleeve clothing. The etching process can release toxic vapors, so it should be performed in a well-ventilated area. The finished product is inspected for defects, such as solder bridges, wrong placement of components and misaligned drill marks.
Bottom Layer
The bottom layer, also known as the ground and power layer, is an actual copper layer that carries signals between layers. Unlike the top layer, which is colored red for reference, the bottom layer is tinned and conductive. The tinned copper is used to connect the components on the board to each other and to the ground and power source.
It is crucial to properly inspect double-layer PCBs, as a minor mistake can have devastating consequences. Inspectors should check the quality of the boards by visually examining them for scratches, cracks and solder bridges, among other defects. They should also test the electrical connections between layers using an ohmmeter or multimeter.
The process of printing a double-layer PCB involves several steps, including applying the copper layer and photoresist film and printing the circuit board design. Then, the board is immersed in etching solution. This solution contains hydrochloric acid and hydrogen peroxide, so it is important to use proper safety measures. This includes wearing gloves, eye protection and a face mask or respirator. In addition, the etching solution must be stored in a well-ventilated area. To prepare the solution, add 120ml of hydrochloric acid and 480ml of distilled water to a glass container. Then, slowly add 60ml of hydrogen peroxide and stir with a plastic spoon. After the solution has reached a light yellow-green color, it is ready to use.
Vias and Through Holes
Vias are holes that connect traces across multiple layers in multilayer PCBs. They can be categorized into three major types based on their size, position and depth. Thru-hole vias are larger and are used for the electrical connection of through-hole components like connectors. Blind and buried vias are smaller and can’t be seen by the naked eye. These are mostly used for signal routing in PCBs.
These are also referred to as “pad-to-pad” connections. Unlike plated thru-holes, these can’t be inspected for defects, so they must be designed and fabricated properly in order to ensure reliable connections. To control the quality of your double-layer PCBs, you can use Visual Inspection and Connectivity Testing to identify defects like scratches, solder bridges, incorrectly positioned components, misaligned drill marks and unconnected traces.
To make a double-layer circuit board, you need premium-quality dielectric materials like FR-4, copper, epoxy-based pre-pregs and conductive tracks. Pre-pregs are semi-cured sheets of material that bind the individual layers together and act as insulation. They’re also useful for creating PCB layout stencils and printing a CAD design on them.
Once you’ve got your material ready, you can start making your double-layer PCB. You’ll need a dark box for the photolithography process, a decent laser printer and some UV exposure chemicals. It’s important to wear an ESD strap while handling your materials so you don’t get charged with static electricity.
Electroplating
With copper on both sides and an insulating layer in between, double-sided PCBs enable circuit connections across the board. These are commonly used in double layer pcb board manufacturer industrial controls and power supplies. This type of PCB also improves signal routing compared to single-layer boards.
Electroplating is a common manufacturing process that uses an electrical current to deposit coatings like zinc, aluminum, nickel and chrome on metals such as steel, copper or brass. It’s used for adding corrosion resistance, aesthetic appeal and other mechanical properties to parts and surfaces. There are different types of plating including rack, continuous and autocatalytic.
In rack plating, the parts are mounted to a “rack” and then immersed in the plating solution. This method provides uniform distribution of the coating since all the parts are plated at the same time. It’s typically used for parts that are difficult to plate using other methods, such as brittle or large pieces.
Etching is a crucial step in the PCB fabrication process. Before the double layer pcb is etched, it’s important to ensure that the photoresist film on the surface is removed and all traces are properly placed. It’s also necessary to carefully mix the etching solution and submerge the circuit board in it until it’s completely etched. Then, it must be rinsed thoroughly to remove all traces of the etching solution.