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 mount applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board design may have all thru-hole parts on the leading or element side, a mix of thru-hole and surface mount on the top side just, a mix of thru-hole and surface area mount parts on the top side and surface mount components on the bottom or circuit side, or surface area mount elements on the leading and bottom sides of the board.
The boards are also used to electrically link the required leads for each component using conductive copper traces. The component pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed as single agreed copper pads and traces on one side of the board just, double agreed 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 surfaces as part of the board production process. A multilayer board includes a variety 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 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 common four layer board design, the internal layers are frequently used to supply power and ground connections, such as a +5 V plane layer and a Ground aircraft layer as the two internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Very complex board designs may have a a great deal 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 integrated circuit plan formats.
There are generally 2 types of product utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, typically about.002 inches thick. Core product resembles a very thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 approaches utilized to build up the desired number of layers. The core stack-up approach, which is an older innovation, utilizes 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 more recent innovation, would have core product as the center layer followed by layers of pre-preg and copper material built up above and below to form the final number of layers needed by the board design, sort of like Dagwood building a sandwich. This technique permits the producer versatility in how the board layer densities are integrated to satisfy the completed product thickness requirements by differing the variety of sheets of pre-preg in each layer. When 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 actions below for most applications.
The procedure of determining materials, processes, and requirements to satisfy the client's specifications for the board design based upon the Gerber file details supplied with the purchase order.
The process of moving the Gerber file information for a layer onto an etch resist film 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 place; newer processes utilize plasma/laser etching rather of chemicals to remove the copper product, enabling finer line definitions.
The procedure of aligning the conductive copper and insulating dielectric layers and pushing them under heat to activate the adhesive in the dielectric layers to form a solid 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. Information on hole area and size is consisted of in the drill drawing file.
The procedure 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 needed when holes are to be drilled through a copper location but the hole ISO 9001 Certification Consultants is not to be plated through. Prevent this procedure 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 actually had a thin layer of solder used; the solder mask protects against ecological damage, provides insulation, secures 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 eventual 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 element classifications and element details to the board. May be used to just the top side or to both sides if components are installed on both top and bottom sides.
The process of separating numerous boards from a panel of similar boards; this process likewise allows cutting notches or slots into the board if needed.
A visual inspection 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 procedure of checking for connection or shorted connections on the boards by methods using a voltage between different points on the board and identifying if an existing flow happens. Depending upon the board complexity, this process might require a specifically developed test component and test program to incorporate with the electrical test system used by the board maker.