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 mount applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board style might have all thru-hole components on the leading or element side, a mix of thru-hole and surface mount on the top side just, a mix of thru-hole and surface mount elements on the top and surface area install components on the bottom or circuit side, or surface install parts on the top and bottom sides of the board.
The boards are also utilized to electrically link the required leads for each component using conductive copper traces. The element pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed as single agreed copper pads and traces on one side of the board only, double sided with 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 consist of a core dielectric product, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is etched away to form the actual copper pads and connection traces on the board surface areas as part of the board manufacturing procedure. A multilayer board includes a variety of layers of dielectric material that has been fertilized with adhesives, and these layers are utilized to separate the layers of copper plating. All these layers are lined up 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 common 4 layer board style, the internal layers are often utilized to offer power and ground connections, such as a +5 V aircraft layer and a Ground plane layer as the two internal layers, with all other circuit and part connections made on the top and bottom layers of the board. Really complicated board designs might have a a great deal of layers to make the various connections for various voltage levels, ground connections, or for linking the many leads on ball grid array devices and other large integrated circuit bundle formats.
There are usually 2 types of product used to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, usually about.002 inches thick. Core product resembles an extremely thin double sided board in that it has a dielectric product, such as Click here 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 design, there are two approaches utilized to build up the desired number of layers. The core stack-up technique, which is an older technology, utilizes a center layer of pre-preg product with a layer of core product above and another layer of core material below. This combination of one pre-preg layer and two core layers would make a 4 layer board.
The movie stack-up method, a more recent innovation, would have core product as the center layer followed by layers of pre-preg and copper product developed above and listed below to form the final variety of layers required by the board design, sort of like Dagwood developing a sandwich. This technique allows the maker flexibility in how the board layer densities are integrated to satisfy the finished item thickness requirements by differing the variety of sheets of pre-preg in each layer. As soon as the product layers are completed, the whole stack is subjected to 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 process of making printed circuit boards follows the actions below for many applications.
The process of determining products, processes, and requirements to satisfy the consumer's specifications for the board design based on the Gerber file info provided with the order.
The process of transferring the Gerber file information for a layer onto an etch withstand movie that is placed on the conductive copper layer.
The conventional process of exposing the copper and other locations unprotected by the etch resist film to a chemical that removes the vulnerable copper, leaving the secured copper pads and traces in place; newer procedures utilize plasma/laser etching rather of chemicals to get rid of the copper material, allowing finer line definitions.
The procedure 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 product.
The process of drilling all of the holes for plated through applications; a second drilling process is used for holes that are not to be plated through. Details on hole area and size is included 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 however the hole is not to be plated through. Prevent this procedure if possible due to the fact that it adds cost to the completed board.
The process of using a protective masking material, 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 protects versus ecological damage, provides insulation, secures versus solder shorts, and secures traces that run between pads.
The process of finishing the pad areas with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will occur at a later date after the parts have actually been positioned.
The process of using the markings for component classifications and element lays out to the board. Might be applied to just the top or to both sides if parts are mounted on both leading and bottom sides.
The process of separating numerous boards from a panel of similar boards; this process also enables cutting notches or slots into the board if required.
A visual evaluation of the boards; also can be the process of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other methods.
The process of checking for connection or shorted connections on the boards by means using a voltage between numerous points on the board and figuring out if a present flow occurs. Relying on the board intricacy, this procedure might require a specifically developed test fixture and test program to incorporate with the electrical test system used by the board maker.