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 area install applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board style might have all thru-hole parts on the top or component side, a mix of thru-hole and surface area mount on the top side just, a mix of thru-hole and surface area install elements on the top side and surface mount elements on the bottom or circuit side, or surface area mount components on the leading and bottom sides of the board.
The boards are likewise used to electrically connect the required leads for each element using conductive copper traces. The element pads and connection traces are etched 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 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 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 production procedure. A multilayer board includes a variety of layers of dielectric material that has been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All these layers are lined ISO 9001 Accreditation Consultants 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 innovations.
In a normal four layer board design, the internal layers are often used to provide power and ground connections, such as a +5 V aircraft layer and a Ground aircraft layer as the two internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Extremely complicated board styles 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 array devices and other large integrated circuit bundle formats.
There are generally 2 types of product 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 product is similar to an extremely thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, usually.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 approaches used to build up the desired variety of layers. The core stack-up technique, which is an older technology, utilizes a center layer of pre-preg product with a layer of core product above and another layer of core product listed below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.
The movie stack-up approach, a newer 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 last variety of layers required by the board design, sort of like Dagwood developing a sandwich. This approach enables the maker versatility in how the board layer thicknesses are integrated to fulfill the completed product density requirements by varying the number of sheets of pre-preg in each layer. As soon as the product layers are completed, the entire 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 producing printed circuit boards follows the actions below for the majority of applications.
The process of identifying materials, processes, and requirements to satisfy the customer's specs for the board style based upon the Gerber file info supplied with the purchase order.
The procedure of transferring the Gerber file data for a layer onto an etch resist movie that is put on the conductive copper layer.
The standard process of exposing the copper and other locations unprotected by the etch withstand movie to a chemical that removes the vulnerable copper, leaving the safeguarded copper pads and traces in place; more recent processes utilize plasma/laser etching rather of chemicals to get rid of the copper material, permitting finer line definitions.
The process of lining up the conductive copper and insulating dielectric layers and pushing them under heat to activate the adhesive in the dielectric layers to form a strong board material.
The process of drilling all the holes for plated through applications; a second drilling procedure is utilized for holes that are not to be plated through. Information on hole location 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 placed in an electrically charged bath of copper.
This is needed when holes are to be drilled through a copper area however the hole is not to be plated through. Avoid this process if possible because it includes cost to the finished 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 applied; the solder mask secures against ecological damage, provides insulation, safeguards against solder shorts, and secures traces that run between pads.
The process of finishing the pad areas with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will occur at a later date after the parts have been positioned.
The procedure of using the markings for element classifications and component details to the board. Might be applied to just the top side or to both sides if parts are installed on both top and bottom sides.
The process of separating multiple boards from a panel of similar boards; this process also allows cutting notches or slots into the board if required.
A visual evaluation of the boards; likewise 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 means using a voltage between different points on the board and figuring out if an existing flow occurs. Relying on the board complexity, this process might need a specifically designed test component and test program to incorporate with the electrical test system utilized by the board manufacturer.