In electronic devices, printed circuit boards, or PCBs, are utilized to mechanically support electronic parts 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 part leads in thru-hole applications. A board style might have all thru-hole parts on the leading or component side, a mix of thru-hole and surface area install on the top side just, a mix of thru-hole and surface area install parts on the top side and surface area mount components on the bottom or circuit side, or surface area install parts on the top and bottom sides of the board.
The boards are also utilized to electrically link the needed leads for each component utilizing conductive copper traces. The part 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 only, double agreed copper pads and traces on the leading and bottom sides of the board, or multilayer styles 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 real copper pads and connection traces on the board surfaces as part of the board production procedure. A multilayer board consists of a variety of layers of dielectric material 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 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 typical four layer board style, the internal layers are often used to provide 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 intricate board styles might have a a great deal of layers to make the numerous connections for different voltage levels, ground connections, or for linking the lots of leads on ball grid range gadgets and other large integrated circuit package formats.
There are usually 2 types of material utilized to build 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 product is similar to a very 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 product with 1 ounce copper layer on each side. In a multilayer board style, there are 2 methods utilized to develop the wanted variety of layers. The core stack-up approach, 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 mix of one pre-preg layer and two core layers would make a 4 layer board.
The movie stack-up method, a more recent technology, 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 style, sort of like Dagwood developing a sandwich. This approach allows the manufacturer versatility in how the board layer densities are combined to meet the finished product thickness requirements by varying the number of sheets of pre-preg in each layer. Once the material layers are finished, the entire stack undergoes 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 producing printed circuit boards follows the actions below for a lot of applications.
The procedure of identifying products, procedures, and requirements to satisfy the customer's requirements for the board style based upon the Gerber file details provided with the purchase order.
The procedure of moving the Gerber file data for a layer onto an etch withstand movie that is put on the conductive copper layer.
The traditional procedure of exposing the copper and other areas unprotected by the etch resist film to a chemical that removes the vulnerable copper, leaving the secured copper pads and traces in location; newer processes use plasma/laser etching instead of chemicals to remove the copper material, allowing finer line definitions.
The process 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 strong board product.
The procedure of drilling all the holes for plated through applications; a second drilling process is used for holes that are not to be plated through. Info on hole place 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 but the hole is not to be plated through. Prevent this procedure if possible because it includes expense to the completed board.
The process of using 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 protects against ecological damage, supplies insulation, protects versus solder shorts, and secures traces that run between pads.
The procedure of finishing the pad locations 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 components have been put.
The process of using the markings for part designations and element lays out to the board. Might be used to just the top side or to both sides if components are mounted on both leading and bottom sides.
The process of separating multiple boards from a panel of identical boards; this process also permits cutting notches or slots into the board if required.
A visual assessment 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 approaches.
The procedure of checking for continuity or shorted ISO 9001 Accreditation Consultants connections on the boards by ways applying a voltage between various points on the board and identifying if an existing circulation happens. Depending upon the board complexity, this process may need a specifically developed test fixture and test program to incorporate with the electrical test system utilized by the board producer.