ISO 9001 consultants
In electronic devices, printed circuit boards, or PCBs, are used to mechanically support electronic elements 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 component leads in thru-hole applications. A board design might have all thru-hole elements 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 mount components on the top side and surface mount elements on the bottom or circuit side, or surface install elements on the leading and bottom sides of the board.
The boards are likewise utilized to electrically connect the needed leads for each element using 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 agreed copper pads and traces on one side of the board only, double sided with copper pads and traces on the leading 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 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 production process. A multilayer board includes a variety of layers of dielectric product that has 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 technologies.
In a common four layer board design, the internal layers are frequently used to offer power and ground connections, such as a +5 V airplane layer and a Ground plane layer as the 2 internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Extremely intricate board designs 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 range gadgets and other large incorporated circuit plan formats.
There are typically two kinds of product utilized to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, usually about.002 inches thick. Core product is similar to a very thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are 2 techniques used to build up the desired variety of layers. The core stack-up technique, which is an older innovation, uses a center layer of pre-preg material with a layer of core material above and another layer of core material listed below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.
The film stack-up approach, a newer technology, would have core material as the center layer followed by layers of pre-preg and copper material built up above and below to form the final variety of layers required by the board style, sort of like Dagwood constructing a sandwich. This technique enables the maker versatility in how the board layer densities are combined to meet the completed product density requirements by differing the number of sheets of pre-preg in each layer. Once the material layers are finished, the whole stack undergoes 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 procedure of manufacturing printed circuit boards follows the actions listed below for the majority of applications.
The process of figuring out products, processes, and requirements to satisfy the client's specifications for the board style based upon the Gerber file info provided 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 areas unprotected by the etch resist film to a chemical that eliminates the unprotected copper, leaving the safeguarded copper pads and traces in location; more recent processes utilize plasma/laser etching rather of chemicals to get rid of the copper material, enabling finer line meanings.
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 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. Info on hole location and size is contained 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. Avoid this process if possible since it includes cost to the completed board.
The procedure of using a protective masking product, 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 safeguards against ecological damage, provides insulation, secures versus solder shorts, and protects traces that run in between pads.
The procedure of finishing the pad locations with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering process that will occur at a later date after the components have actually been placed.
The procedure of applying the markings for part classifications and component outlines to the board. Might be used to just the top or to both sides if components are mounted on both top and bottom sides.
The process of separating multiple boards from a panel of similar boards; this process also allows cutting notches or slots into the board if needed.
A visual assessment of the boards; likewise can be the process of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The process of looking for connection or shorted connections on the boards by ways applying a voltage between numerous points on the board and identifying if a present circulation takes place. Depending upon the board intricacy, this procedure might require a specially created test component and test program to integrate with the electrical test system used by the board maker.