In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic parts which have their connection leads soldered onto copper pads in surface mount applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board style may have all thru-hole parts on the leading or component side, a mix of thru-hole and surface area install on the top just, a mix of thru-hole and surface area install elements on the top and surface mount parts on the bottom or circuit side, or surface area mount components on the leading and bottom sides of the board.
The boards are likewise used to electrically link the needed leads for each part using conductive copper traces. The component pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed as single agreed copper pads and traces on one side of the board only, double agreed copper pads and traces on the top and bottom sides of the board, or multilayer styles with copper pads and traces on top and bottom of board with a variable variety of internal copper layers with traces and connections.
Single or double sided boards consist of a core dielectric material, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is engraved away to form the actual copper pads and connection traces on the board surfaces as part of the board manufacturing process. A multilayer board consists of a number of layers of dielectric material that has been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All of these layers are aligned then bonded into a single board structure under heat and pressure. Multilayer boards with 48 or more layers can be produced with today's innovations.
In a normal 4 layer board style, the internal layers are typically used to provide power and ground connections, such as a +5 V aircraft layer and a Ground airplane layer as the 2 internal layers, with all other circuit and part connections made on the top and bottom layers of the board. Very intricate board styles might have a large number of layers to make the numerous connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid variety gadgets and other large incorporated circuit package formats.
There are usually 2 kinds of product utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, usually about.002 inches thick. Core material is similar to an extremely thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, normally.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are two approaches used to develop the wanted number of layers. The core stack-up approach, which is an older innovation, uses a center layer of pre-preg product with a layer of core product above and another layer of core product listed below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.
The movie stack-up method, a newer technology, would have core material as the center layer followed by layers of pre-preg and copper material developed above and listed below to form the last number of layers required by the board style, sort of like Dagwood building a sandwich. This technique allows the maker versatility in how the board layer densities are integrated to fulfill the completed item thickness requirements by differing the variety of sheets of pre-preg in each layer. When the material layers are completed, the entire stack goes through heat and pressure that triggers the adhesive in the pre-preg to bond the core and pre-preg layers together into a single entity.
The procedure of producing printed circuit boards follows the actions below for many applications.
The procedure of figuring out products, processes, and requirements to fulfill the customer's specs for the board design based upon the Gerber file info provided with the purchase order.
The procedure of transferring the Gerber file information for a layer onto an etch resist movie that is put on the conductive copper layer.
The standard process of exposing the copper and other locations unprotected by the etch resist film to a chemical that eliminates the unprotected copper, leaving the protected copper pads and traces in location; newer procedures utilize plasma/laser etching instead of chemicals to remove the copper material, enabling finer line meanings.
The procedure of aligning the conductive copper and insulating dielectric layers and pressing them under heat to trigger the adhesive in the dielectric layers to form a strong board material.
The process of drilling all of the holes for plated through applications; a second drilling process is utilized for holes that are not to be plated through. Information on hole area and size is contained in the drill drawing file.
The process of applying copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are placed in an electrically charged bath of copper.
This is required when holes are to be drilled through a copper area but the hole is not to be plated through. Click here Prevent this process if possible due to the fact that it adds cost to the finished board.
The process of using a protective masking material, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder applied; the solder mask safeguards against environmental damage, supplies insulation, secures versus solder shorts, and protects traces that run between pads.
The procedure of coating the pad locations with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering process that will take place at a later date after the components have been put.
The procedure of using the markings for element designations and element describes to the board. May be used to just the top or to both sides if parts are installed on both leading and bottom sides.
The process of separating multiple boards from a panel of identical boards; this procedure also permits cutting notches or slots into the board if needed.
A visual inspection of the boards; likewise can be the process of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The process of looking for connection or shorted connections on the boards by ways applying a voltage between various points on the board and figuring out if a current circulation happens. Depending upon the board intricacy, this process might require a specially designed test fixture and test program to incorporate with the electrical test system used by the board manufacturer.