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 mount applications or through rilled holes in the board and copper pads for soldering the component leads in thru-hole applications. A board design might have all thru-hole elements on the leading or part side, a mix of thru-hole and surface mount on the top side just, 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 parts on the leading and bottom sides of the board.
The boards are also used to electrically link the needed leads for each part utilizing conductive copper traces. The component pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are ISO 9001 Accreditation developed as single sided with copper pads and traces on one side of the board only, double agreed 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 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 surfaces 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 lined up and after that 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 common four layer board design, the internal layers are often used to offer power and ground connections, such as a +5 V plane layer and a Ground airplane layer as the 2 internal layers, with all other circuit and component connections made on the leading and bottom layers of the board. Very intricate board designs might have a a great deal of layers to make the numerous connections for different voltage levels, ground connections, or for linking the numerous leads on ball grid array devices and other large integrated circuit bundle formats.
There are typically 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 type, typically about.002 inches thick. Core product resembles an extremely thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are two methods utilized to develop the desired 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 material above and another layer of core product listed below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.
The movie stack-up technique, a more recent technology, would have core product as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the final variety of layers required by the board style, sort of like Dagwood building a sandwich. This method allows the maker versatility in how the board layer thicknesses are integrated to fulfill the finished item thickness requirements by differing the number of sheets of pre-preg in each layer. When the product layers are completed, the whole stack is subjected to 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 below for a lot of applications.
The procedure of identifying products, procedures, and requirements to meet the customer's specifications for the board design based upon the Gerber file details 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 conventional procedure of exposing the copper and other areas unprotected by the etch withstand movie to a chemical that gets rid of the unguarded copper, leaving the secured copper pads and traces in location; more recent processes utilize plasma/laser etching rather of chemicals to get rid of the copper material, allowing finer line meanings.
The procedure of aligning the conductive copper and insulating dielectric layers and pressing them under heat to activate 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 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 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 needed when holes are to be drilled through a copper location however the hole is not to be plated through. Avoid this process if possible since it adds expense to the completed board.
The procedure 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 protects versus ecological damage, provides insulation, safeguards versus solder shorts, and secures traces that run between pads.
The procedure of finish the pad areas 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 been positioned.
The procedure of applying the markings for component classifications and component lays out to the board. May be used to simply the top side or to both sides if parts are installed on both leading and bottom sides.
The process of separating several boards from a panel of identical boards; this process likewise permits cutting notches or slots into the board if needed.
A visual evaluation of the boards; also can be the process of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other methods.
The process of checking for continuity or shorted connections on the boards by means using a voltage in between numerous points on the board and figuring out if an existing circulation happens. Relying on the board complexity, this procedure may need a specifically created test component and test program to integrate with the electrical test system used by the board maker.