In electronic devices, printed circuit boards, or PCBs, are used to mechanically support electronic parts 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 style might have all thru-hole components on the top or element side, a mix of thru-hole and surface area mount on the top side only, a mix of thru-hole and surface area install components on the top side and surface 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 utilized to electrically link the needed leads for each component utilizing conductive copper traces. The part 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 only, 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 the top and bottom of board with a variable number of internal copper layers with traces and connections.
Single or double sided See more 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 real copper pads and connection traces on the board surface areas as part of the board production process. A multilayer board consists of a number 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 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 typical four layer board style, the internal layers are typically utilized to offer power and ground connections, such as a +5 V aircraft layer and a Ground airplane layer as the 2 internal layers, with all other circuit and element connections made on the top and bottom layers of the board. Extremely complicated board styles might have a a great deal of layers to make the numerous connections for various voltage levels, ground connections, or for linking the lots of leads on ball grid array gadgets and other big incorporated circuit plan formats.
There are typically 2 types of product utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet form, typically about.002 inches thick. Core product 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, normally.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are 2 methods utilized to build up the desired number of layers. The core stack-up method, which is an older technology, uses a center layer of pre-preg material with a layer of core product above and another layer of core product 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 material as the center layer followed by layers of pre-preg and copper product developed above and below to form the final variety of layers needed by the board design, sort of like Dagwood constructing a sandwich. This method permits the maker versatility in how the board layer thicknesses are combined to fulfill the finished product density requirements by differing the number of sheets of pre-preg in each layer. As soon as the material layers are finished, the entire stack undergoes 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 procedure of manufacturing printed circuit boards follows the steps listed below for the majority of applications.
The procedure of figuring out products, processes, and requirements to satisfy the customer's specs for the board style based upon the Gerber file info offered with the order.
The procedure of moving the Gerber file information for a layer onto an etch resist movie that is put on the conductive copper layer.
The traditional procedure of exposing the copper and other areas unprotected by the etch withstand film to a chemical that gets rid of the unguarded copper, leaving the secured copper pads and traces in place; more recent procedures utilize plasma/laser etching rather of chemicals to eliminate the copper material, allowing finer line definitions.
The process of lining up the conductive copper and insulating dielectric layers and pressing them under heat to trigger the adhesive in the dielectric layers to form a strong board material.
The procedure 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 consisted of in the drill drawing file.
The procedure 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 however the hole is not to be plated through. Prevent this process if possible due to the fact that it includes expense to the completed board.
The process of applying a protective masking product, 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 versus ecological damage, provides insulation, protects versus solder shorts, and safeguards traces that run in between pads.
The process of finish 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 parts have actually been positioned.
The process of applying the markings for part designations and part outlines to the board. May be used to just the top or to both sides if parts are mounted on both top and bottom sides.
The process of separating several boards from a panel of similar boards; this procedure also permits cutting notches or slots into the board if needed.
A visual evaluation of the boards; likewise can be the process of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The procedure of looking for connection or shorted connections on the boards by means using a voltage between numerous points on the board and figuring out if a current flow happens. Relying on the board complexity, this procedure may require a specifically developed test fixture and test program to incorporate with the electrical test system utilized by the board maker.