In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic elements 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 element leads in thru-hole applications. A board design may have all thru-hole parts on the leading or element side, a mix of thru-hole and surface install on the top side just, a mix of thru-hole and surface area install components on the top side and surface area install elements on the bottom or circuit side, or surface area mount parts on the top and bottom sides of the board.
The boards are also used to electrically connect the needed leads for each element utilizing 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 sided with 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 designs 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 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 surfaces as part of the board manufacturing process. A multilayer board includes 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 these layers are aligned 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 innovations.
In a common 4 layer board style, the internal layers are often utilized to offer power and ground connections, such as a +5 ISO 9001 Certification Consultants V plane layer and a Ground aircraft layer as the 2 internal layers, with all other circuit and element connections made on the top and bottom layers of the board. Very complex board designs might have a large number of layers to make the numerous connections for different voltage levels, ground connections, or for connecting the many leads on ball grid selection gadgets and other big incorporated circuit plan formats.
There are generally two kinds of material used to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains 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 material, such as epoxy fiberglass, with a copper layer deposited on each side, normally.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 methods utilized to develop the desired variety of layers. The core stack-up method, 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 listed below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.
The film stack-up technique, a newer innovation, would have core product as the center layer followed by layers of pre-preg and copper product developed above and below to form the final number of layers required by the board design, sort of like Dagwood building a sandwich. This approach enables the producer flexibility in how the board layer thicknesses are integrated to fulfill the ended up product density requirements by varying the variety of sheets of pre-preg in each layer. When the material layers are finished, 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 manufacturing printed circuit boards follows the steps listed below for most applications.
The process of determining materials, processes, and requirements to satisfy the consumer's specs for the board design based on the Gerber file details offered with the purchase order.
The procedure of transferring the Gerber file data for a layer onto an etch withstand movie that is put on the conductive copper layer.
The conventional procedure of exposing the copper and other locations unprotected by the etch resist movie to a chemical that gets rid of the vulnerable copper, leaving the safeguarded copper pads and traces in location; more recent procedures utilize plasma/laser etching instead of chemicals to eliminate the copper material, permitting finer line meanings.
The process of aligning the conductive copper and insulating dielectric layers and pushing them under heat to trigger the adhesive in the dielectric layers to form a solid board product.
The procedure of drilling all of the holes for plated through applications; a 2nd drilling procedure is utilized for holes that are not to be plated through. Info on hole place and size is consisted of 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 positioned in an electrically charged bath of copper.
This is needed when holes are to be drilled through a copper location however the hole is not to be plated through. Avoid this process if possible since it includes cost to the finished board.
The process 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 applied; the solder mask protects against environmental damage, supplies insulation, protects against solder shorts, and secures traces that run in between pads.
The procedure of covering the pad locations with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will take place at a later date after the components have actually been positioned.
The procedure of using the markings for component classifications and element lays out to the board. Might be applied to just the top side or to both sides if components are mounted on both leading and bottom sides.
The procedure of separating numerous boards from a panel of similar boards; this process also permits cutting notches or slots into the board if required.
A visual evaluation of the boards; likewise can be the procedure of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.
The process of looking for connection or shorted connections on the boards by means using a voltage in between various points on the board and identifying if a current flow takes place. Depending upon the board complexity, this process may need a specifically designed test fixture and test program to integrate with the electrical test system utilized by the board producer.