Circuit Board High Density Interconnection (HDI)
Integrated Circuit Packaging
Integrated circuits are fabricated on semiconductor wafers and typically packaged in a polymer casing. Connections with external circuitry were traditionally made using metal pins soldered to locations on the receiving board. More recently, metal contact pads on both donor and receptor components are connected directly with solder using a technique called ball-grid-array(BGA), see figure 1. This improves the high speed performance of the circuits, since inductance is reduced in connections between the two components. In addition, the external circuitry density can be increased to reduce the package size and improve electronic characteristics.
Process Flow
External circuitry is usually fabricated using lithography and electroplating, leaving raised conducting pathways on a carrier substrate. However, better electrical performance can be achieved by embedding conductors in a suitable dielectric and ensuring ground lines run parallel to signal lines, see figure 2. M-Solv offers a range of laser machining systems to pattern the dielectric directly using ablation, without the additional chemical processes required in lithography. Subsequent electroplating leaves conductive tracks where the dielectric has been patterned.
M-Solv Capabilities
Tracks with 6µm line-space and 9µm depth are currently achievable and may be processed together with larger pads and vias, see figure 4. However, in addition to integrated circuit packaging, M-solv laser machining systems are capable of producing wider tracks over much larger areas for high density circuitry. Typical patterns are 100mm x 50mm.
