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 area mount 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 top or element side, a mix of thru-hole and surface mount on the top just, a mix of thru-hole and surface area mount elements on the top side and surface install parts on the bottom or circuit side, or surface install components on the top and bottom sides of the board.
The boards are likewise used to electrically connect the needed leads for each part using conductive copper traces. The element pads and connection traces are engraved 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 agreed copper pads and traces on the leading and bottom sides of the board, or multilayer styles with copper pads and traces on top and bottom of board with a variable number 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 real copper pads and connection traces on the board surfaces as part of the board production process. A multilayer board includes a number of layers of dielectric product that has actually been fertilized with adhesives, and these layers are utilized to separate the layers of copper plating. All of these layers are lined up 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 common four layer board style, the internal layers are often utilized to supply power and ground connections, such as a +5 V plane layer and a Ground airplane layer as the two internal layers, with all other circuit and component connections made on the leading and bottom layers of the board. Extremely intricate board designs ISO 9001 Certification Consultants might have a large number of layers to make the various connections for different voltage levels, ground connections, or for linking the numerous leads on ball grid array gadgets and other large incorporated circuit bundle formats.
There are normally 2 types of material used to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, generally about.002 inches thick. Core material is similar to a really thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are two approaches utilized to develop the desired 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 2 core layers would make a 4 layer board.
The movie stack-up technique, a more recent innovation, 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 last number of layers needed by the board design, sort of like Dagwood constructing a sandwich. This technique permits the manufacturer flexibility in how the board layer thicknesses are integrated to meet the ended up item thickness requirements by varying the number of sheets of pre-preg in each layer. As soon as the product layers are finished, the whole stack is subjected to 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 steps below for a lot of applications.
The process of identifying products, procedures, and requirements to fulfill the customer's specifications for the board design based on the Gerber file info provided with the order.
The procedure of moving the Gerber file data for a layer onto an etch withstand film that is placed on the conductive copper layer.
The conventional process of exposing the copper and other areas unprotected by the etch withstand movie to a chemical that removes the unprotected copper, leaving the protected copper pads and traces in place; more recent processes utilize plasma/laser etching instead of chemicals to remove the copper material, permitting 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 second drilling procedure is utilized for holes that are not to be plated through. Information on hole place and size is contained 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 since it adds cost to the completed board.
The process of applying a protective masking material, a solder mask, over the bare copper traces or over the copper that has actually had a thin layer of solder used; the solder mask safeguards against ecological damage, provides insulation, protects against solder shorts, and secures traces that run between pads.
The process of finish the pad locations 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 elements have been positioned.
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 components are mounted on both leading and bottom sides.
The procedure of separating multiple boards from a panel of similar boards; this process also enables cutting notches or slots into the board if required.
A visual assessment of the boards; also can be the process of examining wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The procedure of looking for connection or shorted connections on the boards by ways using a voltage between numerous points on the board and determining if an existing circulation occurs. Depending upon the board intricacy, this process may require a specially developed test component and test program to incorporate with the electrical test system used by the board manufacturer.