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 install applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board design may have all thru-hole parts on the top or part side, a mix of thru-hole and surface install on the top side only, a mix of thru-hole and surface area mount components on the top and surface install parts on the bottom or circuit side, or surface mount elements on the leading and bottom sides of the board.
The boards are likewise utilized to electrically link the required leads for each part utilizing conductive copper traces. The component pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are created as single agreed copper pads and traces on one side of the board just, double sided with copper pads and traces on the top 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 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 surface areas as part of the board production procedure. A multilayer board includes a variety of layers of dielectric material that has actually been impregnated with adhesives, and these layers are utilized 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 ISO 9001 Certification Consultants normal four layer board design, the internal layers are often utilized to provide power and ground connections, such as a +5 V aircraft layer and a Ground plane layer as the 2 internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Really complicated board designs may have a large number of layers to make the different connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid variety gadgets and other big integrated circuit package formats.
There are generally two kinds 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 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, typically.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 approaches utilized to build up the desired number of layers. The core stack-up approach, which is an older technology, utilizes a center layer of pre-preg material with a layer of core product above and another layer of core material below. This mix 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 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 needed by the board style, sort of like Dagwood constructing a sandwich. This technique allows the producer versatility in how the board layer densities are integrated to satisfy the ended up item thickness requirements by varying the variety of sheets of pre-preg in each layer. Once the material layers are finished, the whole 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 procedure of producing printed circuit boards follows the steps below for many applications.
The procedure of determining materials, procedures, and requirements to fulfill the client's requirements for the board style based on the Gerber file info offered with the purchase order.
The procedure of moving the Gerber file data for a layer onto an etch resist film 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 unguarded copper, leaving the protected copper pads and traces in place; newer procedures utilize plasma/laser etching rather of chemicals to remove the copper material, permitting finer line definitions.
The process 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 solid board product.
The procedure of drilling all of the holes for plated through applications; a 2nd drilling procedure 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 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. Prevent this process if possible since it includes expense to the finished board.
The procedure 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 used; the solder mask protects against ecological damage, supplies insulation, protects versus solder shorts, and secures 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 occur at a later date after the components have actually been placed.
The process of using the markings for element classifications and element lays out to the board. May be used to simply the top or to both sides if parts are mounted on both leading and bottom sides.
The process of separating multiple boards from a panel of similar boards; this process likewise enables cutting notches or slots into the board if needed.
A visual examination 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 procedure of checking for continuity or shorted connections on the boards by means applying a voltage between numerous points on the board and identifying if a present flow happens. Depending upon the board complexity, this process might require a specially developed test fixture and test program to incorporate with the electrical test system used by the board manufacturer.