How You Can Create a Quality Management System Within Your Organization
Apr 15, 2019
In electronic devices, printed circuit boards, or PCBs, are utilized to mechanically support electronic components which have their connection leads soldered onto copper pads in surface mount applications or through rilled holes in the board and copper pads for soldering the element leads in thru-hole applications. A board design might have all thru-hole elements on the top or element side, a mix of thru-hole and surface mount on the top only, a mix of thru-hole and surface area install elements on the top and surface area install elements on the bottom or circuit side, or surface area install components on the top and bottom sides of the board.
The boards are also utilized to electrically connect the required leads for each element utilizing conductive copper traces. The component pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are created as single sided with copper pads and traces on one side of the board only, double sided with 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 number 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 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 consists of a number of layers of dielectric product that has actually been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All of these layers are lined up 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 four layer board design, the internal layers are frequently utilized to supply power and ground connections, such as a +5 V aircraft layer and a Ground plane 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 a great deal of layers to make the different connections for different voltage levels, ground connections, or for linking the many leads on ball grid selection devices and other large incorporated circuit plan formats.
There are usually 2 kinds of product used to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, typically about.002 inches thick. Core product is similar to an extremely thin double sided board because it has a dielectric product, 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 style, there are two techniques utilized to develop the desired number 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 below. This combination of one pre-preg layer and two core layers would make a 4 layer board.
The film stack-up technique, a more recent innovation, would have core material as the center layer followed by layers of pre-preg and copper product developed above and below to form the final variety of layers needed by the board design, sort of like Dagwood building a sandwich. This method enables the maker versatility in how the board layer thicknesses are combined to fulfill the finished item thickness requirements by varying the variety of sheets of pre-preg in each layer. Once the material layers are completed, the entire stack is subjected to 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 actions listed below for the majority of applications.
The process of determining materials, processes, and requirements to meet the client's specifications for the board style based on the Gerber file details provided with the order.
The process of transferring the Gerber file data for a layer onto an etch withstand film that is put on the conductive copper layer.
The standard procedure of exposing the copper and other areas unprotected by the etch withstand film to a chemical that eliminates the unguarded copper, leaving the secured copper pads and traces in location; more recent procedures use plasma/laser etching rather of chemicals to eliminate the copper product, allowing finer line definitions.
The process of lining up the conductive copper and insulating dielectric layers and pressing them under heat to trigger the adhesive in the dielectric layers to form a strong board material.
The procedure of drilling all of the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated ISO 9001 Accreditation Consultants through. Details 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 needed when holes are to be drilled through a copper area however the hole is not to be plated through. Prevent this procedure if possible due to the fact that it includes expense to the completed 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 ecological damage, provides insulation, secures against solder shorts, and safeguards 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 eventual wave soldering or reflow soldering process that will take place at a later date after the elements have actually been placed.
The procedure of applying the markings for element designations and element outlines to the board. Might be used to just the top side or to both sides if parts are mounted on both leading and bottom sides.
The process of separating multiple boards from a panel of similar boards; this procedure likewise enables cutting notches or slots into the board if needed.
A visual inspection 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 looking for continuity or shorted connections on the boards by ways using a voltage in between numerous points on the board and identifying if an existing circulation happens. Relying on the board intricacy, this process may need a specifically developed test component and test program to integrate with the electrical test system used by the board maker.