ISO 9001 Accreditation
In electronics, 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 part 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 area install on the top side just, a mix of thru-hole and surface install parts on the top side and surface area install parts on the bottom or circuit side, or surface mount components on the top and bottom sides of the board.
The boards are likewise used to electrically connect the needed leads for each part using conductive copper traces. The component pads and connection traces are etched 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 only, double agreed 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 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 actual copper pads and connection traces on the board surface areas as part of the board production procedure. A multilayer board consists of a number 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 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 technologies.
In a typical 4 layer board design, the internal layers are often utilized to provide 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 leading and bottom layers of the board. Really intricate board designs may have a large number of layers to make the various connections for various voltage levels, ground connections, or for connecting the lots of leads on ball grid variety devices and other large incorporated circuit bundle formats.
There are typically two types of material used to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet form, usually about.002 inches thick. Core material resembles an extremely thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, generally.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are two techniques utilized to develop the preferred number of layers. The core stack-up method, which is an older innovation, utilizes a center layer of pre-preg product with a layer of core material above and another layer of core product listed below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.
The movie stack-up technique, a newer 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 last variety of layers needed by the board design, sort of like Dagwood constructing a sandwich. This technique allows the manufacturer flexibility in how the board layer densities are integrated to fulfill the completed product thickness requirements by varying the number of sheets of pre-preg in each layer. As soon as the material layers are completed, the whole stack goes through 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 producing printed circuit boards follows the actions listed below for a lot of applications.
The procedure of identifying products, processes, and requirements to meet the client's specifications for the board style based upon the Gerber file info supplied with the purchase order.
The procedure of transferring the Gerber file data for a layer onto an etch withstand movie that is placed on the conductive copper layer.
The conventional process of exposing the copper and other locations unprotected by the etch withstand film to a chemical that removes the vulnerable copper, leaving the protected copper pads and traces in place; newer processes utilize plasma/laser etching instead of chemicals to remove the copper product, allowing finer line definitions.
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 strong board product.
The procedure of drilling all the holes for plated through applications; a second drilling process is utilized for holes that are not to be plated through. Information on hole location and size is consisted of in the drill drawing file.
The process of using 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 location but the hole is not to be plated through. Avoid this process if possible because 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 actually had a thin layer of solder applied; the solder mask protects versus ecological damage, provides insulation, protects against solder shorts, and protects traces that run between pads.
The process of finishing the pad locations with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will happen at a later date after the elements have been put.
The process of applying the markings for element designations and component outlines to the board. May be applied to simply the top or to both sides if elements are installed on both top and bottom sides.
The process of separating numerous boards from a panel of identical boards; this procedure likewise enables cutting notches or slots into the board if required.
A visual evaluation of the boards; likewise can be the process of examining wall quality for plated through holes in multi-layer boards by cross-sectioning or other approaches.
The procedure of looking for continuity or shorted connections on the boards by methods applying a voltage in between different points on the board and determining if a present flow occurs. Depending upon the board complexity, this procedure might require a specially developed test fixture and test program to incorporate with the electrical test system utilized by the board manufacturer.