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 area install applications or through rilled holes in the board and copper pads for soldering the element leads in thru-hole applications. A board style may have all thru-hole elements on the leading or part side, a mix of thru-hole and surface area mount on the top side only, a mix of thru-hole and surface area mount parts on the top side and surface area install parts on the bottom or circuit side, or surface mount elements on the top and bottom sides of the board.
The boards are also utilized to electrically connect the required leads for each part using conductive copper traces. The element pads and connection traces are etched 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 sided with copper pads and traces on the leading and bottom sides of the board, or multilayer styles 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 material, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is engraved away to form the actual copper pads and connection traces on the board surface areas as part of the board manufacturing procedure. A multilayer board includes a number of layers of dielectric product that has been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All 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 innovations.
In a normal four layer board style, the internal layers are often utilized to supply power and ground connections, such as a +5 V plane layer and a Ground airplane layer as the two internal layers, with all other circuit and component connections made on the leading and bottom layers of the board. Really complex board styles may have a a great deal of layers to make the different connections for various voltage levels, ground connections, or for connecting the many leads on ball grid range gadgets and other big integrated circuit bundle formats.
There are generally two kinds of material used to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, generally about.002 inches thick. Core product resembles a very thin double sided board in that it has a ISO 9001 Certification Consultants
dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 methods utilized to develop the desired variety of layers. The core stack-up technique, which is an older technology, 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 innovation, would have core product as the center layer followed by layers of pre-preg and copper product built up above and listed below to form the final number of layers required by the board design, sort of like Dagwood constructing a sandwich. This method enables the producer versatility in how the board layer thicknesses are integrated to meet the ended up item thickness requirements by differing the variety of sheets of pre-preg in each layer. Once the material layers are completed, 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 actions listed below for most applications.
The process of determining products, processes, and requirements to fulfill the customer's specifications for the board style based on the Gerber file information offered with the purchase order.
The process of moving the Gerber file data for a layer onto an etch resist film that is placed on the conductive copper layer.
The traditional procedure of exposing the copper and other areas unprotected by the etch resist film to a chemical that gets rid of the vulnerable copper, leaving the safeguarded copper pads and traces in place; newer procedures utilize plasma/laser etching instead of chemicals to remove the copper product, allowing 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 solid board material.
The process of drilling all of the holes for plated through applications; a second drilling procedure is utilized for holes that are not to be plated through. Information on hole area and size is included in the drill drawing file.
The procedure of using copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are put in an electrically charged bath of copper.
This is required when holes are to be drilled through a copper area however the hole is not to be plated through. Avoid this process if possible due to the fact that it adds cost to the finished board.
The procedure of applying a protective masking product, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder applied; the solder mask safeguards versus environmental damage, provides insulation, safeguards against solder shorts, and protects traces that run between pads.
The procedure of coating the pad areas 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 put.
The procedure of using the markings for component designations and component describes to the board. May 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 several boards from a panel of identical boards; this procedure likewise allows cutting notches or slots into the board if required.
A visual inspection of the boards; likewise can be the process of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The process of checking for continuity or shorted connections on the boards by ways applying a voltage between various points on the board and identifying if a current circulation occurs. Relying on the board complexity, this procedure might require a specially developed test fixture and test program to incorporate with the electrical test system used by the board manufacturer.