In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic components 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 may have all thru-hole components on the leading or part side, a mix of thru-hole and surface mount on the top only, a mix of thru-hole and surface mount components on the top and surface area install parts on the bottom or circuit side, or surface mount components on the leading and bottom sides of the board.
The boards are likewise utilized to electrically connect the required leads for each component using conductive copper traces. The element pads and connection traces are etched 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 the 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 engraved away to form the actual copper pads and connection traces on the board surface areas as part of the board manufacturing process. A multilayer board consists of a variety of layers of dielectric material that has been impregnated 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 innovations.
In a normal 4 layer board design, the internal layers are often used to provide power and ground connections, such as a +5 V airplane layer and a Ground aircraft layer as the 2 internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Very complicated board styles might have a a great deal of layers to make the different connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid range devices and other big integrated circuit bundle formats.
There are typically two types of material used to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet form, typically about.002 inches thick. Core material resembles a very thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, normally.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 methods used 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 newer technology, would have core product as the center layer followed by layers of pre-preg and copper product built up above and listed below to form the last variety of layers required by the board design, sort of like Dagwood constructing a sandwich. This approach permits the manufacturer versatility in how the board layer densities are combined to fulfill the finished product thickness requirements by varying the variety of sheets of pre-preg in each layer. When the product layers are finished, the whole stack ISO 9001 Accreditation Consultants 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 producing printed circuit boards follows the steps listed below for a lot of applications.
The procedure of determining products, procedures, and requirements to fulfill the customer's specs for the board style based upon the Gerber file information supplied with the order.
The procedure of moving the Gerber file data for a layer onto an etch withstand film that is put on the conductive copper layer.
The standard procedure of exposing the copper and other areas unprotected by the etch resist movie to a chemical that eliminates the vulnerable copper, leaving the safeguarded copper pads and traces in place; more recent processes utilize plasma/laser etching rather of chemicals to get rid of the copper material, permitting finer line definitions.
The process of aligning the conductive copper and insulating dielectric layers and pressing them under heat to activate the adhesive in the dielectric layers to form a solid board material.
The process of drilling all the holes for plated through applications; a 2nd drilling procedure is utilized for holes that are not to be plated through. Details on hole location 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 placed in an electrically charged bath of copper.
This is needed when holes are to be drilled through a copper area however the hole is not to be plated through. Prevent this procedure if possible since it adds cost to the ended up board.
The procedure 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 used; the solder mask safeguards versus ecological damage, supplies insulation, protects versus solder shorts, and protects traces that run in between pads.
The procedure of finishing the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering procedure that will occur at a later date after the components have actually been positioned.
The process of using the markings for part designations and component lays out to the board. May be applied to just the top side or to both sides if parts are mounted on both leading and bottom sides.
The procedure of separating several boards from a panel of identical boards; this process likewise allows cutting notches or slots into the board if required.
A visual examination of the boards; likewise can be the process of examining wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The process of checking for connection or shorted connections on the boards by ways applying a voltage in between different points on the board and identifying if an existing circulation takes place. Depending upon the board intricacy, this process may require a specifically designed test fixture and test program to incorporate with the electrical test system used by the board producer.