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 area mount 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 components on the leading or part side, ISO 9001 Accreditation Consultants a mix of thru-hole and surface area install on the top side just, a mix of thru-hole and surface mount components on the top side and surface area mount parts on the bottom or circuit side, or surface area mount elements on the leading and bottom sides of the board.
The boards are likewise used to electrically link the needed leads for each element utilizing conductive copper traces. The part pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are created as single agreed copper pads and traces on one side of the board only, double sided with 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 variety 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 surface areas as part of the board production process. A multilayer board consists of 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 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 normal four layer board design, the internal layers are often used to supply power and ground connections, such as a +5 V plane layer and a Ground aircraft layer as the 2 internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Really complex board designs might have a large number of layers to make the different connections for different voltage levels, ground connections, or for linking the many leads on ball grid array devices and other large integrated circuit plan formats.
There are normally 2 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 kind, normally about.002 inches thick. Core product resembles a very thin double sided board because it has a dielectric material, 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 style, there are two techniques utilized to build up the preferred variety of layers. The core stack-up technique, which is an older innovation, uses a center layer of pre-preg material with a layer of core material 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 newer technology, would have core product as the center layer followed by layers of pre-preg and copper material developed above and below to form the final number of layers required by the board design, sort of like Dagwood developing a sandwich. This method enables the maker versatility in how the board layer densities are combined to satisfy the completed product thickness requirements by differing the variety of sheets of pre-preg in each layer. Once the product layers are finished, the whole stack goes through 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 steps below for many applications.
The process of determining products, procedures, and requirements to meet the consumer's specifications for the board style based on the Gerber file information provided with the purchase order.
The procedure of transferring the Gerber file information for a layer onto an etch resist film that is placed on the conductive copper layer.
The conventional procedure of exposing the copper and other areas unprotected by the etch resist film to a chemical that eliminates the vulnerable copper, leaving the safeguarded copper pads and traces in location; more recent procedures use plasma/laser etching instead of chemicals to remove the copper material, allowing finer line definitions.
The procedure 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 product.
The process of drilling all the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated through. Information on hole location and size is consisted of 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 required when holes are to be drilled through a copper area but the hole is not to be plated through. Prevent this procedure if possible since it adds cost to the finished board.
The process of using 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 protects against ecological damage, provides insulation, protects against solder shorts, and protects traces that run in between pads.
The procedure of finishing 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 parts have actually been placed.
The process of applying the markings for element classifications and element describes to the board. May be used to just the top side or to both sides if elements 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 required.
A visual assessment 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 methods.
The process of looking for connection or shorted connections on the boards by methods using a voltage in between different points on the board and identifying if a present circulation takes place. Depending upon the board intricacy, this process might need a specifically created test fixture and test program to incorporate with the electrical test system used by the board maker.