In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic elements 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 design may have all thru-hole elements on the leading or element side, a mix of thru-hole and surface area mount on the top side just, a mix of thru-hole and surface mount components on the top and surface mount components on the bottom or circuit side, or surface mount components on the leading and bottom sides of the board.
The boards are likewise used to electrically link the required leads for each component utilizing 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 just, 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 the top and bottom of board with a variable number 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 etched away to form the actual copper pads and connection traces on the board surfaces as part of the board manufacturing procedure. A multilayer board consists of 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 aligned 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 normal four layer board design, the internal layers are typically used to supply power and ground connections, such as a +5 V airplane layer and a Ground airplane layer as the 2 internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Very learn the facts here now complicated board styles may have a large number of layers to make the different connections for various voltage levels, ground connections, or for connecting the lots of leads on ball grid variety gadgets and other large incorporated circuit plan formats.
There are usually 2 kinds of material utilized to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, typically about.002 inches thick. Core material resembles a very thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, normally.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 methods used to build up the preferred number of layers. The core stack-up technique, which is an older innovation, utilizes a center layer of pre-preg material 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 film stack-up method, a newer innovation, would have core product as the center layer followed by layers of pre-preg and copper material developed above and below to form the final variety of layers required by the board design, sort of like Dagwood developing a sandwich. This technique enables the maker versatility in how the board layer thicknesses are combined to fulfill the finished product thickness requirements by differing the number of sheets of pre-preg in each layer. When the material layers are completed, the entire 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 manufacturing printed circuit boards follows the actions listed below for most applications.
The process of determining products, processes, and requirements to meet the customer's specifications for the board design based on the Gerber file details supplied with the purchase order.
The process of moving the Gerber file information for a layer onto an etch resist movie that is placed on the conductive copper layer.
The standard procedure of exposing the copper and other locations unprotected by the etch resist movie to a chemical that removes the unguarded copper, leaving the secured copper pads and traces in location; more recent procedures utilize plasma/laser etching instead of chemicals to get rid of the copper product, allowing 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 material.
The procedure of drilling all the holes for plated through applications; a 2nd 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 procedure of using 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 location however the hole is not to be plated through. Prevent this process if possible due to the fact that it adds expense to the finished board.
The process 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 used; the solder mask safeguards against environmental damage, supplies insulation, safeguards against solder shorts, and safeguards traces that run 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 procedure that will occur at a later date after the elements have been put.
The procedure of using the markings for part classifications and element lays out to the board. May be used to simply the top side or to both sides if components are mounted on both top and bottom sides.
The process of separating multiple boards from a panel of identical boards; this process likewise permits cutting notches or slots into the board if needed.
A visual inspection 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 methods.
The procedure of looking for continuity or shorted connections on the boards by means using a voltage in between numerous points on the board and identifying if a present circulation occurs. Depending upon the board complexity, this procedure might require a specially created test component and test program to integrate with the electrical test system used by the board manufacturer.