Wise Organizations Set up State-of-the-Art QM Systems


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 area install 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 parts on the top or part side, a mix of thru-hole and surface area install on the top side only, a mix of thru-hole and surface area mount components on the top side and surface mount parts on the bottom or circuit side, or surface install parts on the leading and bottom sides of the board.

The boards are also utilized to electrically connect the required leads for each component 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 developed as single sided with copper pads and traces on one side of the board only, double sided with 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 number of internal copper layers with traces and connections.

Single or double sided boards include a core dielectric product, 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 surfaces as part of the board manufacturing process. A multilayer board consists of a number 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 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 innovations.

In a typical 4 layer board design, the internal layers are often utilized to provide 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 top and bottom layers of the board. Extremely complicated board designs might have a a great deal of layers to make the numerous connections for various voltage levels, ground connections, or for connecting the numerous leads on ball grid variety gadgets and other big incorporated circuit plan formats.

There are typically two types of product used to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, normally about.002 inches thick. Core material is similar to a very thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, normally.030 density dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 approaches used to develop the preferred variety of layers. The core stack-up approach, which is an older technology, uses a center layer of pre-preg product with a layer of core product above and another layer of core material listed below. This combination of one pre-preg layer and two core layers would make a 4 layer board.

The film stack-up method, a more recent technology, would have core product as the center layer followed by layers of pre-preg and copper product built up above and ISO 9001 Certification Consultants below to form the final variety of layers required by the board style, sort of like Dagwood building a sandwich. This method allows the maker versatility in how the board layer densities are combined to satisfy the ended up product density requirements by varying the number of sheets of pre-preg in each layer. As soon as the product layers are finished, the entire 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 making printed circuit boards follows the steps below for most applications.

The process of figuring out materials, processes, and requirements to fulfill the client's specs for the board style based on the Gerber file details offered 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 traditional process of exposing the copper and other areas unprotected by the etch resist movie to a chemical that removes the unguarded copper, leaving the secured copper pads and traces in location; more recent processes use plasma/laser etching instead of chemicals to get rid of the copper material, permitting 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 solid board product.

The procedure of drilling all of the holes for plated through applications; a 2nd drilling procedure is used for holes that are not to be plated through. Information on hole location and size is consisted of 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 placed 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 adds expense to the completed board.

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

The process of covering 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 components have actually been put.

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

The procedure of separating several boards from a panel of identical boards; this procedure also enables cutting notches or slots into the board if needed.

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

The procedure of looking for continuity or shorted connections on the boards by means using a voltage between various points on the board and determining if a current flow takes place. Depending upon the board intricacy, this process might require a specially developed test fixture and test program to incorporate with the electrical test system utilized by the board manufacturer.