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 area install applications or through rilled holes in the board and copper pads for soldering the element leads in thru-hole applications. A board design might have all thru-hole parts on the leading or component side, a mix of thru-hole and surface area mount on the top side only, a mix of thru-hole and surface area mount elements on the top side and surface area install elements on the bottom or circuit side, or surface mount elements on the leading 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 component pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed as single sided with 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 include 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 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 of 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 common four layer board style, the internal layers are typically utilized to supply power and ground connections, such as a +5 V aircraft layer and a Ground aircraft layer as the 2 internal layers, with all other circuit and element connections made on the top and bottom layers of the board. Really complicated board designs may have a a great deal of layers to make the numerous connections for different voltage levels, ground connections, or for connecting the lots of leads on ball grid variety gadgets and other big incorporated circuit plan formats.
There are usually two kinds of product used to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, typically about.002 inches thick. Core material is similar to an extremely thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, normally.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 techniques utilized to build up the preferred variety of layers. The core stack-up approach, which is an older technology, uses a center layer of pre-preg product 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 technique, a newer innovation, would have core material as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the last variety of layers required by the board style, sort of like Dagwood developing a sandwich. This approach enables the maker versatility in how the board layer thicknesses are combined to satisfy the finished item density requirements by differing the variety of sheets of pre-preg in each layer. When the material layers are completed, 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 process of making printed circuit boards follows the actions below for the majority of applications.
The process of determining products, processes, and requirements to satisfy the customer's requirements for the board design based on the Gerber file info supplied with the purchase order.
The process of transferring the Gerber file information for a layer onto an etch resist movie that is placed on the conductive copper layer.
The standard process of exposing the copper and other locations unprotected by the etch resist movie to a chemical that removes the unguarded copper, leaving the safeguarded copper pads and traces in location; more recent processes use plasma/laser etching rather of chemicals to eliminate the copper material, allowing 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 material.
The procedure of drilling all of the holes for plated through applications; a 2nd drilling process is utilized for holes that are not to be plated through. Information 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 positioned in an electrically charged bath of copper.
This is required when holes are to be drilled through a copper location however the hole is not to be plated through. Prevent this procedure if possible since it includes expense to the completed 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 applied; the solder mask safeguards versus environmental damage, supplies insulation, safeguards against solder shorts, and protects traces that run in between pads.
The process of finishing the pad locations 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 elements have actually been positioned.
The process of applying the markings for part classifications and part describes to the board. May be applied to simply the top or to both sides if parts are mounted on both leading and bottom sides.
The procedure of separating numerous boards from a panel of identical boards; this procedure also permits 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 [source] sources tell me applying a voltage in between various points on the board and determining if a current flow occurs. Depending upon the board intricacy, this process might need a specially designed test component and test program to integrate with the electrical test system utilized by the board producer.