QM Systems Opinions



In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic components 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 may have all thru-hole elements on the top or part side, a mix of thru-hole and surface area mount ISO 9001 Certification Consultants on the top side only, a mix of thru-hole and surface mount parts on the top side and surface area install components on the bottom or circuit side, or surface install components on the top and bottom sides of the board.

The boards are also utilized to electrically link the required leads for each element utilizing conductive copper traces. The part pads and connection traces are etched 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 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 product, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is engraved away to form the actual 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 material that has actually been fertilized with adhesives, and these layers are utilized 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 typical four layer board style, the internal layers are frequently utilized to offer 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 part connections made on the leading and bottom layers of the board. Really complicated board designs might have a large number of layers to make the numerous connections for different voltage levels, ground connections, or for linking the lots of leads on ball grid range devices and other big integrated circuit package formats.

There are generally 2 types of product used to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet type, generally 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, typically.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are 2 techniques utilized to build up the wanted variety of layers. The core stack-up approach, 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 material below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.

The film stack-up technique, a more recent 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 number of layers required by the board style, sort of like Dagwood constructing a sandwich. This technique enables the manufacturer versatility in how the board layer thicknesses are combined to satisfy the finished product density requirements by differing the variety of sheets of pre-preg in each layer. As soon as the material layers are completed, the entire stack undergoes 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 a lot of applications.

The process of identifying products, processes, and requirements to meet the client's requirements for the board design based upon the Gerber file details offered with the purchase order.

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

The traditional procedure of exposing the copper and other locations unprotected by the etch resist film to a chemical that gets rid of the vulnerable copper, leaving the protected copper pads and traces in location; newer processes utilize plasma/laser etching rather of chemicals to remove the copper product, enabling finer line meanings.

The process of lining up 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 process of drilling all the holes for plated through applications; a second drilling process is used for holes that are not to be plated through. Information on hole area and size is consisted of 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 needed when holes are to be drilled through a copper location but the hole is not to be plated through. Prevent this process if possible since it adds expense to the finished board.

The procedure 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 used; the solder mask protects versus ecological damage, supplies insulation, protects against solder shorts, and protects traces that run in between pads.

The process of covering the pad locations with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering process that will take place at a later date after the parts have been put.

The procedure of applying the markings for element classifications and part outlines to the board. May be applied to just the top or to both sides if components are installed on both top and bottom sides.

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

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

The procedure of looking for continuity or shorted connections on the boards by means applying a voltage between numerous points on the board and identifying if a current flow takes place. Relying on the board intricacy, this process may need a specially designed test fixture and test program to incorporate with the electrical test system utilized by the board maker.