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 mount applications or ISO 9001 Certification Consultants through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board design might have all thru-hole elements on the leading or element side, a mix of thru-hole and surface area mount on the top only, a mix of thru-hole and surface install parts on the top side and surface area mount parts on the bottom or circuit side, or surface area mount components on the leading and bottom sides of the board.
The boards are also used to electrically connect the required 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 developed as single sided with 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 the 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 product, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is etched 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 variety of layers of dielectric material that has been fertilized with adhesives, and these layers are utilized to separate the layers of copper plating. All 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 common 4 layer board style, the internal layers are typically used to offer 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 component connections made on the top and bottom layers of the board. Really complicated board styles might have a large number of layers to make the numerous connections for various voltage levels, ground connections, or for linking the many leads on ball grid range gadgets and other big integrated circuit plan formats.
There are generally two kinds of product utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, generally about.002 inches thick. Core material is similar to an extremely thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are two methods used to build up the wanted number of layers. The core stack-up method, which is an older technology, uses a center layer of pre-preg product with a layer of core product 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 approach, a more recent technology, would have core material as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the last number of layers required by the board design, sort of like Dagwood developing a sandwich. This method permits the maker versatility in how the board layer thicknesses are combined to satisfy the completed item thickness requirements by differing the number of sheets of pre-preg in each layer. When the material layers are completed, the entire stack goes through 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 identifying products, procedures, and requirements to fulfill the customer's requirements for the board design based upon the Gerber file details provided with the purchase order.
The process of moving the Gerber file data for a layer onto an etch withstand movie that is placed on the conductive copper layer.
The standard procedure of exposing the copper and other locations unprotected by the etch withstand film to a chemical that eliminates the unguarded copper, leaving the safeguarded copper pads and traces in place; newer processes use plasma/laser etching rather of chemicals to eliminate the copper material, permitting 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 process of drilling all of 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 contained 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 required when holes are to be drilled through a copper area but the hole is not to be plated through. Avoid this procedure if possible since it includes expense to the ended up board.
The procedure of using a protective masking material, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder used; the solder mask safeguards against ecological damage, supplies insulation, protects versus solder shorts, and protects traces that run between pads.
The process of covering the pad locations with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will happen at a later date after the parts have actually been positioned.
The procedure of applying the markings for part classifications and part lays out to the board. May be applied to just the top side or to both sides if components are mounted on both top and bottom sides.
The procedure of separating several boards from a panel of identical boards; this procedure also enables cutting notches or slots into the board if required.
A visual assessment of the boards; likewise can be the procedure of examining wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The procedure of checking for continuity or shorted connections on the boards by means applying a voltage between various points on the board and figuring out if an existing circulation takes place. Depending upon the board complexity, this procedure may need a specifically created test fixture and test program to incorporate with the electrical test system utilized by the board manufacturer.