The Most Up-To-Date Info About QM Systems

ISO 9001 Accreditation

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

The boards are likewise used to electrically connect the required leads for each component using conductive copper traces. The component pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are created as single sided with copper pads and traces on one side of the board only, double agreed copper pads and traces on the top and bottom sides of the board, or multilayer designs 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 actual copper pads and connection traces on the board surfaces as part of the board manufacturing process. A multilayer board consists of a variety 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 of 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 common 4 layer board style, the internal layers are frequently used 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 element connections made on the leading and bottom layers of the board. Very complicated board designs may have a large number of layers to make the various connections for different voltage levels, ground connections, or for linking the lots of leads on ball grid variety devices and other big integrated circuit bundle formats.

There are generally two types of product used to construct a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, generally about.002 inches thick. Core product resembles a very thin double sided board because it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are two methods utilized to build up the wanted number of layers. The core stack-up approach, which is an older innovation, 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 film stack-up approach, a more recent technology, would have core material as the center layer followed by layers of pre-preg and copper material built up above and below to form the final variety of layers needed by the board design, sort of like Dagwood building a sandwich. This method allows the manufacturer versatility in how the board layer thicknesses are integrated to meet the completed product thickness requirements by varying the number of sheets of pre-preg in each layer. Once the product layers are completed, the whole stack goes through 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 making printed circuit boards follows the steps below for a lot of applications.

The process of identifying materials, processes, and requirements to meet the client's specifications for the board design based on the Gerber file information provided with the 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 areas unprotected by the etch resist film to a chemical that eliminates the vulnerable copper, leaving the protected copper pads and traces in location; more recent procedures use plasma/laser etching instead of chemicals to get rid of the copper material, allowing finer line definitions.

The procedure of aligning the conductive copper and insulating dielectric layers and pushing them under heat to activate the adhesive in the dielectric layers to form a solid board material.

The process of drilling all the holes for plated through applications; a second drilling procedure is used for holes that are not to be plated through. Info 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 however the hole is not to be plated through. Avoid this procedure if possible since it adds expense to the finished board.

The procedure 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 environmental damage, offers insulation, secures versus solder shorts, and secures traces that run between pads.

The process of coating 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 elements have actually been placed.

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

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

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 connection or shorted connections on the boards by ways using a voltage between numerous points on the board and determining if a present flow occurs. Relying on the board complexity, this process might need a specifically created test component and test program to incorporate with the electrical test system used by the board maker.

Posted on Tags