In electronic devices, printed circuit boards, or PCBs, are used 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 element leads in thru-hole applications. A board design may have all thru-hole components on the leading or component side, a mix of thru-hole and surface area install on the top only, a mix of thru-hole and surface area mount parts on the top side and surface area mount components on the bottom or circuit side, or surface install parts on the top and bottom sides of the board.
The boards are likewise used to electrically connect the required leads for each component using conductive copper traces. The component pads and connection traces are engraved 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 just, double sided with 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 number 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 etched away to form the real copper pads and connection traces on the board surface areas as part of the board manufacturing process. A multilayer board consists of a variety of layers of dielectric material that has actually been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All of these layers are aligned then 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 frequently utilized to offer power and ground connections, such as a +5 V plane layer and a Ground aircraft layer as the two internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Extremely complex board styles may have a a great deal of layers to make the numerous connections for different voltage levels, ground connections, or for connecting the lots of leads on ball grid selection gadgets and other big integrated circuit plan formats.
There are usually two types of product utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated ISO 9001 Certification Consultants with an adhesive, and remains in sheet kind, usually about.002 inches thick. Core material is similar to a very thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, usually.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are two methods utilized to build up the desired variety of layers. The core stack-up approach, which is an older technology, utilizes a center layer of pre-preg material with a layer of core material above and another layer of core material listed 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 innovation, would have core material as the center layer followed by layers of pre-preg and copper product built up above and below to form the final number of layers needed by the board style, sort of like Dagwood constructing a sandwich. This technique enables the manufacturer flexibility in how the board layer thicknesses are integrated to satisfy the completed item thickness requirements by differing the number of sheets of pre-preg in each layer. When the product layers are finished, the whole stack undergoes 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 process of manufacturing printed circuit boards follows the steps below for the majority of applications.
The process of determining products, processes, and requirements to satisfy the customer's requirements for the board style based on the Gerber file details provided with the order.
The process of moving the Gerber file data for a layer onto an etch resist movie that is put on the conductive copper layer.
The standard procedure of exposing the copper and other areas unprotected by the etch resist film to a chemical that removes the vulnerable copper, leaving the safeguarded copper pads and traces in place; newer procedures use plasma/laser etching rather of chemicals to get rid of the copper material, enabling finer line definitions.
The process of lining up the conductive copper and insulating dielectric layers and pressing them under heat to activate the adhesive in the dielectric layers to form a solid board material.
The procedure of drilling all the holes for plated through applications; a 2nd drilling procedure is utilized for holes that are not to be plated through. Information on hole location 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 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. Prevent this process if possible since it adds expense to the finished board.
The procedure 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 secures versus environmental damage, offers insulation, protects versus 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 procedure that will take place at a later date after the components have actually been positioned.
The procedure of using the markings for element designations and component details to the board. May be used to just the top 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 procedure also permits cutting notches or slots into the board if needed.
A visual examination 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 process of checking for connection or shorted connections on the boards by ways using a voltage between various points on the board and identifying if a current flow occurs. Relying on the board complexity, this process might need a specifically designed test fixture and test program to integrate with the electrical test system used by the board maker.