Simply Quality Systems



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 area mount applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board style 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 only, a mix of thru-hole and surface area install components on the top and surface area install parts on the bottom or circuit side, or surface area install components on the top and bottom sides of the board.

The boards are likewise utilized to electrically link the needed leads for each part utilizing conductive copper traces. The element pads and connection traces are engraved 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 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 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 etched away to form the actual copper pads and connection traces on the board surfaces as part of the board manufacturing procedure. A multilayer board consists of a number of layers of dielectric material that has actually been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All of 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 4 layer board design, the internal layers are typically utilized to supply power and ground connections, such as a +5 V aircraft layer and a Ground airplane layer as the 2 internal layers, with all other circuit and part connections made on the top and bottom layers of the board. Really complex board styles might have a large number of layers to make the different connections for different voltage levels, ground connections, or for linking the many leads on ball grid variety devices and other big integrated circuit package formats.

There are usually two kinds of material utilized to construct 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 material is similar to a really thin double sided board because it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, normally.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are 2 approaches utilized to develop the desired number of layers. The core stack-up method, which is an older innovation, uses a center layer of pre-preg product with a layer of core material above and another layer of core product listed below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.

The movie stack-up approach, a more recent innovation, would have core product as the center layer followed by layers of pre-preg and copper material developed above and listed below to form the last variety of layers required by the board style, sort of like Dagwood constructing a sandwich. This approach allows the maker versatility in how the board layer densities are combined to satisfy the ended up item density requirements by varying the number of sheets of pre-preg in each layer. Once the product layers are completed, the whole stack goes through 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 manufacturing printed circuit boards follows the actions listed below for many applications.

The process of figuring out products, processes, and requirements to satisfy the customer's requirements for the board style based upon the Gerber file info provided with the order.

The procedure of moving the Gerber file information for a layer onto an etch resist film that is placed on the conductive copper layer.

The standard process of exposing the copper and other areas unprotected by the etch withstand movie to a chemical that eliminates the vulnerable copper, leaving the secured copper pads and traces in location; newer processes use plasma/laser etching instead of chemicals to get rid of the copper product, allowing finer line meanings.

The procedure 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 procedure of drilling all the holes for plated through applications; a 2nd drilling process is utilized for holes that are not to be plated through. Information on hole area and size is contained 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 area however the hole is not to be plated through. Avoid this procedure if possible because it adds expense to the ended up board.

The process of using a protective masking material, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder applied; the solder mask protects versus ecological damage, offers insulation, protects versus solder shorts, and protects traces that run between pads.

The procedure of finish the pad More interesting details here 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 positioned.

The process of applying the markings for component classifications and element outlines to the board. May be used to simply the top side or to both sides if parts are mounted on both leading and bottom sides.

The procedure of separating several boards from a panel of similar boards; this procedure also allows cutting notches or slots into the board if required.

A visual assessment of the boards; also can be the process of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.

The procedure of checking for continuity or shorted connections on the boards by means applying a voltage in between various points on the board and identifying if an existing circulation happens. Depending upon the board complexity, this procedure might require a specially designed test fixture and test program to integrate with the electrical test system used by the board maker.