All About Quality Systems

In electronics, printed circuit boards, or PCBs, are used to mechanically support electronic elements 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 element leads in thru-hole applications. A board style might have all thru-hole elements on the top or component side, a mix of thru-hole and surface area install on the top only, a mix of thru-hole and surface install parts on the top and surface area mount components on the bottom or circuit side, or surface area install components on the leading and bottom sides of the board.

The boards are also used to electrically connect the required 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 developed as single agreed 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 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 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 surface areas as part of the board manufacturing process. A multilayer board includes a variety of layers of dielectric product that has been fertilized with adhesives, and these layers are utilized to separate the layers of copper plating. All of these layers are lined up 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 four layer board design, the internal layers are frequently utilized to offer power and ground connections, such as a +5 V plane layer and a Ground plane layer as the two internal layers, with all other circuit and part connections made on the leading and bottom layers of the board. Very complex board styles may have a a great deal of layers to make the various connections for different voltage levels, ground connections, or for linking the lots of leads on ball grid array devices and other big incorporated circuit bundle formats.

There are typically 2 types of product utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet kind, generally about.002 inches thick. Core product is similar to a very thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer deposited on each side, typically.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are two approaches utilized to build up the preferred number of layers. The core stack-up method, which is an older technology, utilizes 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 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 material built up above and listed below to form the last variety of layers needed by the board design, sort of like Dagwood developing a sandwich. This technique permits the manufacturer flexibility in how the board layer densities are combined to meet the ended up product density requirements by varying the variety of sheets of pre-preg in each layer. When the material layers are completed, 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 process of manufacturing printed circuit boards follows the steps below for a lot of applications.

The procedure of figuring out products, processes, and requirements to meet the client's specs for the board design based on the Gerber file information supplied with the purchase order.

The procedure of moving the Gerber file data for a layer onto an etch resist movie that is put on the conductive copper layer.

The conventional process of exposing the copper and other locations unprotected by the etch resist movie to a chemical that eliminates the unguarded copper, leaving the safeguarded copper pads and traces in place; more recent procedures use plasma/laser etching rather of chemicals to eliminate the copper product, allowing finer line meanings.

The process of lining up the conductive copper and insulating dielectric layers and pressing them under heat to activate the adhesive in the dielectric layers to form a strong board product.

The process of drilling all the holes for plated through applications; a second drilling procedure is utilized for holes that are not to be plated through. Info on hole place 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 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 procedure if possible due to the fact that it includes expense to the ended up board.

The procedure 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 against environmental damage, offers insulation, secures versus solder shorts, and secures traces that run in More interesting details here 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 process that will occur at a later date after the elements have been positioned.

The procedure of applying the markings for element designations and element describes to the board. Might be used to simply the top or to both sides if elements are installed on both top and bottom sides.

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

A visual assessment of the boards; also can be the procedure of examining 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 applying a voltage in between different points on the board and figuring out if an existing circulation happens. Relying on the board intricacy, this procedure might require a specially designed test component and test program to integrate with the electrical test system used by the board manufacturer.