Quality Management Systems Standpoints

Apr 15, 2019  


In electronics, printed circuit boards, or PCBs, are used 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 design may have all thru-hole parts on the leading or element side, a mix of thru-hole and surface area mount on the top just, a mix of thru-hole and surface install elements on the top and surface mount parts on the bottom or circuit side, or surface area install elements on the leading and bottom sides of the board.

The boards are likewise used to electrically connect the required leads for each part 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 only, double agreed copper pads and traces on the leading and bottom sides of the board, or multilayer designs with copper pads and traces on 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 engraved away to form the real copper pads and connection traces on the board surfaces as part of the board manufacturing process. A multilayer board includes a number of layers of dielectric product that has actually 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 innovations.

In a typical 4 layer board style, the internal layers are often used to provide power and ground connections, such as a +5 V plane layer and a Ground plane layer as the 2 internal layers, with all other circuit and part connections made on the top and bottom layers of the board. Very complex board designs might have a large number of layers to make the different connections for various voltage levels, ground connections, or for connecting the many leads on ball grid array devices and other large integrated circuit bundle formats.

There are typically 2 kinds 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 form, generally about.002 inches thick. Core product is similar to an extremely 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 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are two methods used to develop the desired variety 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 mix of one pre-preg layer and 2 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 material built up above and listed below to form the final number of layers required by the board design, sort of like Dagwood constructing a sandwich. This technique allows the producer versatility in how the board layer densities are combined to fulfill the ended up product density requirements by differing the variety of sheets of pre-preg in each layer. Once the material layers are finished, the entire stack is subjected to 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 the majority of applications.

The process of figuring out products, processes, and requirements to fulfill the customer's specs for the board style based upon More interesting details here the Gerber file details provided with the order.

The process of moving the Gerber file data for a layer onto an etch withstand film that is put on the conductive copper layer.

The traditional procedure of exposing the copper and other locations unprotected by the etch resist movie to a chemical that gets rid of the unprotected copper, leaving the protected copper pads and traces in place; more recent processes utilize plasma/laser etching rather of chemicals to remove the copper product, allowing finer line definitions.

The procedure of aligning 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 of the holes for plated through applications; a 2nd drilling procedure is utilized for holes that are not to be plated through. Information on hole place and size is included 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 area but the hole is not to be plated through. Avoid this procedure if possible because it includes expense to the finished board.

The process of applying a protective masking material, 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 secures against ecological damage, supplies insulation, protects versus solder shorts, and protects traces that run in between pads.

The procedure of finish the pad areas with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will take place at a later date after the elements have been put.

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

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

A visual inspection of the boards; likewise can be the procedure of checking wall quality for plated through holes in multi-layer boards by cross-sectioning or other techniques.

The process of looking for continuity or shorted connections on the boards by methods applying a voltage between numerous points on the board and figuring out if an existing circulation takes place. Relying on the board complexity, this procedure might require a specifically created test fixture and test program to integrate with the electrical test system utilized by the board manufacturer.