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 part leads in thru-hole applications. A board design may have all thru-hole elements on the leading or component side, a mix of thru-hole and surface area install on the top side only, a mix of thru-hole and surface area mount parts on the top and surface mount parts on the bottom or circuit side, or surface mount components on the top and bottom sides of the board.
The boards are also used to electrically connect 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 top 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 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 surface areas as part of the board manufacturing procedure. A multilayer board includes a number of layers of dielectric material that has actually been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All of these layers are aligned 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 4 layer board design, the internal layers are typically utilized to provide power and ground connections, such as a +5 V aircraft layer and a Ground airplane layer as the two internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Really complicated board styles may have a large number of layers to make the different connections for different voltage levels, ground connections, or for connecting the lots of leads on ball grid variety gadgets and other big integrated circuit plan formats.
There are normally 2 types of product used to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, usually about.002 inches thick. Core material is similar to a really thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, generally.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 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 product 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 approach, a newer 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 required by the board design, sort of like Dagwood developing a sandwich. This approach allows the manufacturer versatility in how the board layer densities are combined to meet the ended up product density requirements by differing 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 triggers the adhesive in the pre-preg to bond the core and pre-preg layers together into a single entity.
The procedure ISO 9001 consultants of making printed circuit boards follows the actions below for many applications.
The procedure of identifying products, processes, and requirements to fulfill the customer'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 standard procedure of exposing the copper and other locations unprotected by the etch withstand movie to a chemical that removes the unprotected copper, leaving the safeguarded copper pads and traces in place; more recent procedures use plasma/laser etching rather of chemicals to eliminate the copper product, permitting 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 procedure 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 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 positioned in an electrically charged bath of copper.
This is required when holes are to be drilled through a copper location but the hole is not to be plated through. Prevent this process if possible due to the fact that it adds expense to the completed board.
The procedure 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 protects against ecological damage, provides insulation, safeguards against solder shorts, and protects traces that run in between pads.
The process of coating the pad areas 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 actually been put.
The process of using the markings for element classifications and component outlines to the board. May be applied to simply the top side or to both sides if components are mounted on both top and bottom sides.
The process of separating multiple boards from a panel of identical boards; this procedure likewise allows cutting notches or slots into the board if needed.
A visual evaluation 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 approaches.
The procedure of checking for continuity or shorted connections on the boards by means using a voltage in between numerous points on the board and figuring out if a current circulation happens. Relying on the board complexity, this process may require a specially created test component and test program to integrate with the electrical test system utilized by the board producer.