Indian PCB industry

Multiwire is a patented technique of interconnection which uses machine-routed insulated wires embedded in a non-conducting matrix (often plastic resin). It was used during the 1980s and 1990s. (Kollmorgen Technologies Corp, U.S. Patent 4,175,816 filed 1978) Multiwire is still available in 2010 through Hitachi. There are other competitive discrete wiring technologies that have been developed (Jumatech , layered sheets). Since it was quite easy to stack interconnections (wires) inside the embedding matrix, the approach allowed designers to forget completely about the routing of wires (usually a time-consuming operation of PCB design): Anywhere the designer needs a connection, the machine will draw a wire in straight line from one location/pin to another. This led to very short design times (no complex algorithms to use even for high density designs) as well as reduced crosstalk (which is worse when wires run parallel to each other—which almost never happens i...

Often encountered materials: FR-2  (Flame Retardant 2), phenolic paper or phenolic cotton paper, paper impregnated with a phenol formaldehyde resin. Cheap, common in low-end consumer electronics with single-sided boards. Electrical properties inferior to FR-4. Poor arc resistance. Generally rated to 105 °C. Resin composition varies by supplier. FR-4  (Flame Retardant 4), a woven fiberglass cloth impregnated with an epoxy resin. Low water absorption (up to about 0.15%), good insulation properties, good arc resistance. Well-proven, properties well understood by manufacturers. Very common, workhorse of the industry. Several grades with somewhat different properties are available. Typically rated to 130 °C. Thin FR-4, about 0.1 mm, can be used for bendable circuitboards. Many different grades exist, with varying parameters; versions are with higher T g , higher tracking resistance, etc. Aluminium , or  metal core boa...

Excluding exotic products using special materials or processes all printed circuit boards manufactured today can be built using the following four materials: Laminates Copper-clad laminates Resin impregnated B-stage cloth (Pre-preg) Copper foil Laminates Table 1 Standard laminate thickness per ANSI/IPC-D-275 IPC laminate number Thickness in inches Thickness in millimeters IPC laminate number Thickness in inches Thickness in millimeters L1 0.002 0.05 L9 0.028 0.70 L2 0.004 0.10 L10 0.035 0.90 L3 0.006 0.15 L11 0.043 1.10 L4 0.008 0.20 L12 0.055 1.40 L5 0.010 0.25 L13 0.059 1.50 L6 0.012 0.30 L14 0.075 1.90 L7 0.016 0.40 L15 0.090 2.30 L8 0.020 0.50 L16 0.122 3.10 Jump up   Although this specification has been superseded and the new specification does not list standard sizes, these are still the most common sizes stocked and ordered for manufacturer. Key substrate parameters Laminates are manufactured b...

Through-hole technology Through-hole PCB technology almost completely replaced earlier electronics assembly techniques such as point-to-point construction. From the second generation of computers in the 1950s until surface-mount technology became popular in the late 1980s, every component on a typical PCB was a through-hole component.The first PCBs used through-hole technology, mounting electronic components by leads inserted through holes on one side of the board and soldered onto copper traces on the other side. Boards may be single-sided, with an unplated component side, or more compact double-sided boards, with components soldered on both sides. Horizontal installation of through-hole parts with two axial leads (such as resistors, capacitors, and diodes) is done by bending the leads 90 degrees in the same direction, inserting the part in the board (often bending leads located on the back of the board in opposite directions to improve the part'...

Areas that should not be soldered may be covered with solder resist (solder mask). One of the most common solder resists used today is called "LPI" (liquid photoimageable solder mask).  A photo-sensitive coating is applied to the surface of the PWB, then exposed to light through the solder mask image film, and finally developed where the unexposed areas are washed away. Dry film solder mask is similar to the dry film used to image the PWB for plating or etching. After being laminated to the PWB surface it is imaged and develop as LPI. Once common but no longer commonly used because of its low accuracy and resolution is to screen print epoxy ink. Solder resist also provides protection from the environment. Legend printing Silk screen printing epoxy ink was the established method. It was so common that legend is often misnamed silk or silkscreen. Liquid photo imaging is a more accurate method than screen printing. Ink jet printing is new but increasingly us...

The inner layers are given a complete machine inspection before lamination because afterwards mistakes cannot be corrected. The automatic optical inspection system scans the board and compares it with the digital image generated from the original design data. Multi-layer printed circuit boards have trace layers inside the board. This is achieved by laminating a stack of materials in a press by applying pressure and heat for a period of time. This results in an inseparable one piece product. For example, a four-layer PCB can be fabricated by starting from a two-sided copper-clad laminate, etch the circuitry on both sides, then laminate to the top and bottom pre-preg and copper foil. It is then drilled, plated, and etched again to get traces on top and bottom layers. Drilling Plating and coating Holes may be made conductive, by electroplating or inserting metal eyelets (hollow), to electrically and thermally connect board layers. Some conductive holes are intended for the insert...