Electronics use printed circuit boards (or PCBs) to mechanically support electronic component. The connection leads are soldered onto copper pads in surface-mount applications, through rilled holes on the board, or soldered to copper pads for soldering in through-hole applications. One board design could have all through hole components on its top or component side. Another board design might have a mixture of through-hole or surface mount components only on the top, circuit side or both.
These boards can also be used to connect each component’s required leads using conductive copper trace. Copper sheets are laminated onto a nonconductive substrate to create the component pads and connection tracks. The printed circuit boards can be designed with copper traces and pads on one side only, double-sided with copper traces and copper pads on both the top and bottom, or multilayer with copper traces and copper pads on the top and the bottom with a variable amount of copper layers with traces, connections, and trace.
Boards can be single- or double-sided. They are made from a core dielectric material such as FR-4 epoxy glass fiber with copper plating on either one or both. This copper plating is removed during board manufacturing to create the copper pads and connections traces on the board surface. Multilayer boards are made up of several layers of dielectric material, which have been coated with adhesives. These layers can be used to separate copper plating layers. Under heat and pressure, all of the layers are aligned then bonded together to form a single board structure. Today’s technology can produce multilayer boards with 48 layers or more. For more info about Circuit Board Protection Potting, Visit our website.
The internal layers of a four-layer board are used to provide power connections. For example, a +5V layer and a ground layer can be used as power connections. All other connections and circuit connections will be made on the top or bottom layers. Complex board designs might have many layers for making connections to different voltage levels and ground connections.
A multilayer board can be made from two types of materials. Pre-preg material consists of thin layers made from fiberglass that have been pre-impregnated using an adhesive. It is usually in sheet form and about.002 inches thick. The core material is similar in appearance to a thin double-sided board. It has a dielectric material such as epoxy fiberglass with a copper layer. This layer is usually.030 thick with a 1 ounce copper layer. There are two ways to make a multilayer board. Core stack-up, an older technology, uses a core layer of pre-preg material, a layer above, and another layer below. A four-layer board would be made from this combination of one core layer and two pre-preg layers.
A newer technology is the film stack-up. This would use core material as the central layer, followed by layers pre-preg or copper material that are built up to form the required number of layers for the board design. It’s a bit like Dagwood making a sandwich. The manufacturer can adjust the thickness of the layers to meet their product thickness requirements. This allows them to vary the number of pre-preg sheets in each layer. After the material layers have been completed, the whole stack is heated and pressurized to cause the adhesive in pre-preg to bond core and prepreg layers together to form one entity.
For most applications, the process for manufacturing printed circuit boards is as follows:
The Basic Steps to Make Printed Circuit Boards
1. Setup is the process of determining the materials, processes and requirements needed to meet the customer’s specifications for the board design. This is based on the Gerber data provided with the purchase order.
2. Imaging is the transfer of Gerber data for a layer onto an Etch Resist Film that is then placed on the conductive Copper layer.
3. Etching is the traditional method of exposing copper and other unprotected areas to a chemical. The unprotected copper remains in place. Newer processes use plasma/laser to remove copper material. This allows for finer line definitions.
4. Multilayer pressing – This is the act of aligning the conductive and insulating copper layers, and pressing them under heat in order to activate the adhesives in the dielectric layer to form a solidboard material.
5. Drilling is the process of drilling all holes for plated-through applications. A second drilling process can be used for holes that cannot be plated through. The drill drawing file contains information about hole size and location.
6. Copper plating is the process of applying copper plating on the pads, traces and drilled through holes that will be plated through. Boards are then placed in an electrically charged copper bath.
7. If holes need to be drilled through copper, but not plated through, this is called second drilling. This process is not recommended as it can increase the cost of the finished board.
8. Masking is the application of a protective masking material (a solder mask) over copper traces. The solder mask protects from environmental damage, provides insulation and protects trace between pads.
9. Finishing – This is the process of covering the pad areas with a thin layer solder to prepare for wave soldering and reflow soldering processes that will be performed after the components are placed.
10. Silk Screening is the process of applying markings to the board for component designations or component outlines. If components are mounted on both the top and bottom sides, they can be applied to either one or both sides.
11. Routing is the process of separating multiple boards out of a panel of identical boards. This process allows for cutting slots or notches into the board, if necessary.
12. Quality Control – This is a visual inspection of boards. It can also be used to inspect wall quality for plated holes in multilayer boards using cross-sectioning, or other methods.
13. Electrical Testing – This is the procedure of testing for continuity and shorted connections by applying voltage to various points on the board. The current flow is determined. This process can be complicated depending on the board’s complexity. A specially designed test fixture or program may be required to integrate with an electrical test system used for this purpose by the manufacturer. Get more info about Conformal Coating Adhesive, Visit here: www.deepmaterialcn.com
All leads are connected electrically by the Printed Circuit Board. Copper traces are used to do this. The copper traces on the board are conductive, but not the board. When the first PCBs were invented, they were only one-sided. Copper engravings were only present on one side of the board when they first appeared. Modern PCBs now have copper engravings on both the sides of their boards. This allows them to hold more components in a smaller space. Multi-layered PCBs, which are currently in production, are also available.
