As experienced manufacturers of PCB from pcbnet.com, we will share some of our knowledge about the background, history, and design of PCB fabrication. A printed circuit board (PCB) is an independent unit of interconnected components installed in electronic devices like computer systems and mobile phones. The circuits consist of a thin deposit of conducting material, which is “printed” on an insulating board called the substrate.
We place each electronic component on the substrate and solder it to the interconnecting circuits. Along the edges of the substrate, there are contact fingers that function as connectors to external devices or other PCBs.
Major Types of PCB Construction
- Single-sided – has components connected on one side of the board.
- Double-sided – we use this when there is too much number of components for a single-sided board. On each side, we drill holes across the substrate in the right locations and plate the holes using a conducting material to create electrical connections between the circuits.
- Multi-layered – the substrate consists of layers of circuits that are separated by layers of insulation. To simplify the circuit pattern, we connect the electrical components on the surface through plated holes that we drill down to the right circuit layer.
Manufacturing Methods of Printed Circuit Board
Components on a PCB are connected to the circuits electrically with these methods:
- Through-hole technology – every component uses leads or thin wires that pass through holes in the substrate and through soldering, they are attached to pads on the opposite side. Friction and gravity between the sides of the holes and the leads hold the components in position until they are soldered.
- Surface mount technology (SMT) – stubby L-shaped or J-shaped legs on every component directly connect the circuits. A solder paste is put on the point of connection to keep the components steady until the solder is “reflowed” or melted using an oven to construct the final connection. This PCB fabrication method needs better care while placing the components, but it does not involve the drilling process and it does not have connection pads that are essential with through-hole technology.
History of PCB
A printed circuit board was developed from electrical connection systems used in the 1850s. Originally, metal rods or strips were used to connect electrical components attached to wooden bases. After some time, wires that are connected to screw terminals replaced the metal strips, and metal chassis replaced the wooden bases.
However, more compact and smaller designs were needed because of the higher operating needs of products with circuit boards. Charles Ducas from the US applied for a patent in 1925 for a method of making an electrical path on an insulated layer by means of a process of printing across a stencil using electrically conductive inks. “Printed circuit” or “printed wiring” was developed because of this method.
Paul Eisler from the UK submitted a patent in 1943 for a method of etching the circuits or conductive patterns on a copper foil coating that is attached to a non-conductive, glass reinforced base. This method only became popular when the transistor was made available for commercial use in the 1950s.
Prior to that, the sizes of the components were so big that the conventional wiring and mounting techniques were all that was required. However, because of the introduction of transistors, the components became really small. Manufacturers started relying on PCBs to decrease the overall size of the product.
In 1961, a US firm called Hazeltyne patented the PCB fabrication method of through-hole technology, along with the use of this method in a multi-layer printed circuit board. The subsequent growth in closely spaced electrical pathways and component density established a new generation in PCB design. In the 1970s, integrated circuit chips were developed, which were immediately included into the PCB board design and assembly techniques.
Every board has a unique purpose for a certain product and we design it so that it will accomplish that purpose in the space allocated. Our board designers use CAD (computer-aided design) systems that have special software to arrange the circuit pattern. We also lay out the position of the holes for contact points or component leads. This information is converted into commands to a drilling machine that is computer numerical-controlled or the programmed solder paste equipment used in the PCB manufacturing process.
After laying out the circuit pattern, we print out a mask or negative image with the actual size of the printed circuit board using a clear plastic sheet. On this negative image, the circuit pattern appears as clear and the areas in black are not part of the pattern.
If you want to know more about printed circuit board, their basic design and Manufacturing Methods, so you just visit our website pcbnet.com.