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 element leads in thru-hole applications. A board style might have all thru-hole elements on the top or component side, a mix of thru-hole and surface mount on the top side only, a mix of thru-hole and surface area install parts on the top and surface install components on the bottom or circuit side, or surface area mount components on the leading and bottom sides of the board.
The boards are also 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 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 include 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 real copper pads and connection traces on the board surface areas as part of the board manufacturing procedure. A multilayer board consists of a variety of layers of dielectric product 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 normal four layer board design, the internal layers are typically used to provide 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 element connections made on the leading and bottom layers of the board. Very complex board styles might have a large number of layers to make the different connections for different voltage levels, ground connections, or for connecting the lots of leads on ball grid array devices and other large integrated circuit package formats.
There are typically two types of product utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, generally about.002 inches thick. Core material resembles an extremely thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 approaches used to develop the wanted variety of layers. The core stack-up approach, which is an older innovation, utilizes a center layer of pre-preg material with a layer of core material above and another layer of core material listed below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.
The movie stack-up approach, a newer technology, would have core material 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 design, sort of like Dagwood developing a sandwich. This technique allows the producer flexibility in how the board layer thicknesses are integrated to fulfill the finished product thickness requirements by differing the number of sheets of pre-preg in each layer. Once the product layers are finished, the whole stack undergoes 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 Click here of manufacturing printed circuit boards follows the steps below for most applications.
The process of identifying materials, procedures, and requirements to satisfy the consumer's specs for the board design based upon the Gerber file information offered with the order.
The procedure of transferring the Gerber file data for a layer onto an etch withstand film that is placed on the conductive copper layer.
The traditional procedure of exposing the copper and other areas unprotected by the etch resist movie to a chemical that gets rid of the unguarded copper, leaving the protected copper pads and traces in location; newer processes use plasma/laser etching instead of chemicals to remove the copper product, permitting finer line meanings.
The procedure of lining up 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 procedure of drilling all the holes for plated through applications; a second drilling process is utilized for holes that are not to be plated through. Info on hole location and size is consisted of 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 area but 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 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 applied; the solder mask secures against ecological damage, supplies insulation, secures versus solder shorts, and safeguards traces that run between pads.
The process of finishing the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will happen at a later date after the components have actually been put.
The procedure of applying the markings for part designations and component describes to the board. May be used to just the top or to both sides if elements are installed on both top and bottom sides.
The procedure of separating numerous boards from a panel of identical boards; this procedure also allows cutting notches or slots into the board if needed.
A visual assessment of the boards; also can be the process of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other methods.
The procedure of checking for connection or shorted connections on the boards by ways using a voltage between various points on the board and identifying if a present circulation happens. Depending upon the board intricacy, this process may require a specially designed test fixture and test program to incorporate with the electrical test system utilized by the board producer.