Quality Management Systems Guide



In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic parts 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 style may have all thru-hole elements on the leading or component side, a mix of thru-hole and surface area mount on the top side just, a mix of thru-hole and surface area install parts on the top side and surface mount elements on the bottom or circuit side, or surface area install elements on the leading and bottom sides of the board.

The boards are also used to electrically connect the needed leads for each element utilizing conductive copper traces. The part pads and connection traces are engraved 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 just, double agreed 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 real copper pads and connection traces on the board surface areas as part of the board production process. A multilayer board consists of a number of layers of dielectric product that has actually 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 technologies.

In a common four layer board style, the internal layers are typically utilized to supply power and ground connections, such as a +5 V airplane layer and a Ground airplane layer as the 2 internal layers, with all other circuit and element connections made on the leading and bottom layers of the board. Very complicated board styles might have a a great deal of layers to make the various connections for various voltage levels, ground connections, or for connecting the lots of leads on ball grid selection gadgets and other big integrated circuit package formats.

There are generally 2 types of material utilized to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, usually about.002 inches thick. Core product is similar to a really thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer transferred on each side, normally.030 thickness dielectric product ISO 9001 consultants with 1 ounce copper layer on each side. In a multilayer board style, there are 2 methods utilized to build up the desired number of layers. The core stack-up method, 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 below. This mix 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 product as the center layer followed by layers of pre-preg and copper material built up above and listed below to form the final variety of layers required by the board style, sort of like Dagwood developing a sandwich. This technique permits the producer flexibility in how the board layer densities are combined to satisfy the ended up product thickness requirements by differing the number of sheets of pre-preg in each layer. When the product layers are finished, 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 procedure of producing printed circuit boards follows the actions below for the majority of applications.

The process of identifying materials, procedures, and requirements to fulfill the consumer's requirements for the board style based upon the Gerber file details offered with the order.

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

The conventional process of exposing the copper and other locations unprotected by the etch resist film to a chemical that removes the vulnerable copper, leaving the protected copper pads and traces in place; newer procedures use plasma/laser etching instead of chemicals to eliminate the copper material, permitting finer line meanings.

The procedure of aligning 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 the holes for plated through applications; a second drilling procedure is used 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 put in an electrically charged bath of copper.

This is needed when holes are to be drilled through a copper location however the hole is not to be plated through. Avoid this process if possible due to the fact that it includes expense to the ended up board.

The process 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 protects versus environmental damage, provides insulation, safeguards against solder shorts, and safeguards traces that run between pads.

The process of finishing the pad areas 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 parts have been put.

The procedure of applying the markings for component designations and part describes to the board. May be used to just the top side or to both sides if elements are mounted on both top and bottom sides.

The procedure of separating multiple boards from a panel of similar boards; this process likewise enables 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 techniques.

The process of checking for connection or shorted connections on the boards by methods using a voltage in between various points on the board and figuring out if a present flow happens. Depending upon the board complexity, this procedure might require a specifically developed test component and test program to integrate with the electrical test system used by the board manufacturer.