In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic components which have their connection leads soldered onto copper pads in surface area install 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 top or component side, a mix of thru-hole and surface area mount on the top just, a mix of thru-hole and surface area install parts on the top side and surface area install components on the bottom or circuit side, or surface mount components on the top and bottom sides of the board.
The boards are also used to electrically link the needed leads for each element 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 designed as single sided with copper pads and traces on one side of the board just, double agreed copper pads and traces on the top and bottom sides of the board, or multilayer styles with copper pads and traces on the top and bottom of board with a variable number 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 actual copper pads and connection traces on the board surface areas as part of the board production procedure. A multilayer board consists of a variety of layers of dielectric material that has been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All 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 typical 4 layer board style, the internal layers are typically used to offer power and ground connections, such as a +5 V plane layer and a Ground airplane layer as the 2 internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Really complicated board designs may have a a great deal of layers to make the various connections for different voltage levels, ground connections, or for linking the many leads on ball grid variety gadgets and other large integrated circuit package formats.
There are typically two types of product utilized to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, normally about.002 inches thick. Core product is similar to a very thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are 2 techniques utilized to build up the preferred variety of layers. The core stack-up technique, which is an older technology, utilizes a center layer of pre-preg material with a layer of core https://www.smore.com/gw2q9 product above and another layer of core product below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.
The film stack-up technique, a more recent innovation, would have core product as the center layer followed by layers of pre-preg and copper material developed above and listed below to form the final variety of layers required by the board style, sort of like Dagwood constructing a sandwich. This method enables the maker versatility in how the board layer thicknesses are integrated to satisfy the ended up item density requirements by differing the variety of sheets of pre-preg in each layer. When the material layers are finished, the entire stack is subjected to 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 making printed circuit boards follows the actions below for most applications.
The procedure of determining products, processes, and requirements to fulfill the customer's requirements for the board design based upon the Gerber file information provided with the purchase order.
The procedure of moving the Gerber file data for a layer onto an etch resist movie that is placed on the conductive copper layer.
The standard procedure of exposing the copper and other locations unprotected by the etch resist film to a chemical that eliminates the unprotected copper, leaving the secured copper pads and traces in place; newer procedures utilize plasma/laser etching instead of chemicals to get rid of the copper product, enabling finer line definitions.
The process of aligning the conductive copper and insulating dielectric layers and pushing them under heat to activate the adhesive in the dielectric layers to form a solid board product.
The procedure of drilling all the holes for plated through applications; a second drilling procedure is utilized for holes that are not to be plated through. Info on hole location and size is contained in the drill drawing file.
The process of using copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are positioned 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. Prevent this process if possible because it adds expense to the ended up board.
The procedure of applying a protective masking material, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder used; the solder mask secures versus ecological damage, offers insulation, secures versus solder shorts, and safeguards traces that run between pads.
The process of covering 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 put.
The procedure of using the markings for element designations and element details to the board. May be applied to simply the top or to both sides if parts are mounted on both top and bottom sides.
The procedure of separating multiple boards from a panel of identical boards; this process also enables cutting notches or slots into the board if required.
A visual evaluation of the boards; likewise can be the procedure of examining wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The process of checking for continuity or shorted connections on the boards by methods using a voltage in between different points on the board and determining if an existing circulation happens. Relying on the board intricacy, this procedure may require a specifically created test component and test program to incorporate with the electrical test system utilized by the board manufacturer.