In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic elements which have their connection leads soldered onto copper pads in surface install applications or through rilled holes in the board and copper pads for soldering the element leads in thru-hole applications. A board style might have all thru-hole parts on the top or element side, a mix of thru-hole and surface area mount on the top side just, a mix of thru-hole and surface install parts on the top and surface area install elements on the bottom or circuit side, or surface area mount parts on the top and bottom sides of the board.
The boards are likewise used to electrically link the required leads for each component using conductive copper traces. The component pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed as single sided with copper pads and traces on one side of the board only, double agreed copper pads and traces on the leading and bottom sides of the board, or multilayer designs 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 include a core dielectric product, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is engraved away to form the real 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 product that has actually been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All these layers are lined up and then bonded into a single board structure under heat and pressure. Multilayer boards with 48 or more layers can be produced with today's technologies.
In a normal 4 layer board design, the internal layers are frequently used to offer power and ground connections, such as a +5 V airplane layer and a Ground plane layer as the 2 internal layers, with all other circuit and component connections made on the leading and bottom layers of the board. Very intricate board designs may have a large number of layers to make the numerous connections for different voltage levels, ground connections, or for linking the numerous leads on ball grid selection devices and other big incorporated circuit package formats.
There are usually 2 types of material used to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, normally about.002 inches thick. Core product 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 density dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are 2 techniques utilized to build up the wanted variety of layers. The core stack-up method, which is an older technology, 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 two core layers would make a 4 layer board.
The movie stack-up approach, a more recent innovation, would have core material as the center layer followed by layers of pre-preg and copper product developed above and listed below to form the final number of layers required by the board style, sort of like Dagwood constructing a sandwich. This approach allows the manufacturer versatility in how the board layer thicknesses are combined to meet the completed product thickness requirements by differing the number of sheets of pre-preg in each layer. As soon as the product layers are finished, the entire stack goes through heat and pressure that causes the adhesive in the pre-preg to bond the core and pre-preg layers together into a single entity.
The process of manufacturing printed circuit boards follows the actions below for a lot of applications.
The process of identifying products, processes, and requirements to meet the customer's specs for the board design based upon the Gerber file info supplied with the order.
The process of transferring the Gerber file More interesting details here data for a layer onto an etch resist film that is placed on the conductive copper layer.
The conventional process of exposing the copper and other areas unprotected by the etch resist film to a chemical that gets rid of the vulnerable copper, leaving the protected copper pads and traces in location; newer procedures utilize plasma/laser etching instead of chemicals to get rid of the copper product, allowing finer line meanings.
The process of aligning the conductive copper and insulating dielectric layers and pushing them under heat to trigger the adhesive in the dielectric layers to form a strong board material.
The process of drilling all the holes for plated through applications; a second drilling process is used for holes that are not to be plated through. Details on hole place and size is consisted of in the drill drawing file.
The procedure of applying copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are put in an electrically charged bath of copper.
This is needed when holes are to be drilled through a copper location but the hole is not to be plated through. Avoid this process if possible because it includes cost to the ended up board.
The process of using a protective masking product, a solder mask, over the bare copper traces or over the copper that has actually had a thin layer of solder applied; the solder mask safeguards versus environmental damage, provides insulation, protects against solder shorts, and secures traces that run between pads.
The process of finish the pad locations with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will occur at a later date after the parts have been placed.
The process of applying the markings for component classifications and component describes to the board. Might be used to just the top side or to both sides if components are mounted on both top and bottom sides.
The procedure of separating multiple boards from a panel of similar boards; this procedure likewise allows cutting notches or slots into the board if required.
A visual evaluation of the boards; likewise can be the process of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The process of checking for connection or shorted connections on the boards by means using a voltage between numerous points on the board and determining if a present flow occurs. Depending upon the board intricacy, this procedure might require a specially created test component and test program to integrate with the electrical test system used by the board producer.