TQM Systems Opinions



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 element leads in thru-hole applications. A board design might have all thru-hole parts on the leading or component side, a mix of thru-hole and surface mount on the top side just, a mix of thru-hole and surface area install parts on the top side and surface mount components on the bottom or circuit side, or surface mount elements on the leading and bottom sides of the board.

The boards are also utilized to electrically connect the required leads for each part utilizing conductive copper traces. The component pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed as single sided with 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 etched away to form the actual copper pads and connection traces on the board surfaces as part of the board production procedure. A multilayer board includes a number of layers of dielectric product that has actually been fertilized with adhesives, and these layers are used to separate the layers of copper plating. All these layers are aligned 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 normal 4 layer board design, the internal layers are often utilized to supply 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 element connections made on the leading and bottom layers of the board. Very intricate board designs might have a large number of layers to make the different connections for different voltage levels, ground connections, or for linking the many leads on ball grid range devices and other big incorporated circuit bundle formats.

There are usually 2 kinds of material 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 because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, typically.030 density dielectric product with 1 ounce copper layer on each side. In a multilayer board style, there are two techniques utilized to develop 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 product listed below. This combination of one pre-preg layer and 2 core layers would make a 4 layer board.

The film stack-up approach, a newer innovation, would have core product as the center layer followed by layers of pre-preg and copper material developed above and below to form the final number of layers needed by the board style, sort of like Dagwood building a sandwich. This method allows the producer versatility in how the board layer thicknesses are integrated to meet the finished item thickness requirements by varying the number of sheets of pre-preg in each layer. When the material layers are finished, the whole 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 procedure of manufacturing printed circuit boards follows the actions below for a lot of applications.

The procedure of identifying products, processes, and requirements to meet the See more here client's specifications for the board design based on the Gerber file information provided with the purchase order.

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

The standard procedure of exposing the copper and other locations unprotected by the etch resist movie to a chemical that eliminates the vulnerable copper, leaving the secured copper pads and traces in location; newer processes utilize plasma/laser etching instead of chemicals to remove the copper product, enabling finer line definitions.

The procedure 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 process of drilling all the holes for plated through applications; a 2nd drilling procedure is used for holes that are not to be plated through. Details on hole area and size is consisted of 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 positioned in an electrically charged bath of copper.

This is required when holes are to be drilled through a copper area but the hole is not to be plated through. Prevent this process if possible because it adds expense to the finished board.

The process of using 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 safeguards against ecological damage, provides insulation, protects against solder shorts, and protects traces that run between pads.

The procedure of covering the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering procedure that will occur at a later date after the parts have been placed.

The process of applying the markings for part designations and element lays out to the board. May be used to simply the top or to both sides if parts are installed on both leading and bottom sides.

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

A visual inspection of the boards; also can be the procedure 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 ways applying a voltage in between numerous points on the board and determining if a present circulation occurs. Depending upon the board complexity, this procedure may need a specially developed test fixture and test program to incorporate with the electrical test system utilized by the board manufacturer.