In-Circuit Test Vector Synthesis for High Density Assembly Modifications
Vector synthesis for modified assemblies requires delta netlist verification, BSDL timing re-validation, and algorithmic backdrive current bounds.
Micro-via
Meaning
An extremely small electrical connection between layers of a high-density printed circuit board provides the routing density required for modern fine-pitch packages. By implementing a micro-via, designers can route signals through build-up layers using holes that are laser-drilled and plated. This design feature typically occupies a fraction of the space of a conventional drilled through-hole.
Physical Fabrication
Laser technology drills the shallow blind holes with extreme precision to stop exactly at the target copper pad. The hole is then filled with conductive copper using specialized electroplating processes. This process creates a solid metal post that can be stacked directly on top of another.
Mechanical Reliability
Thermal expansion differences between the copper fill and the surrounding epoxy substrate can create mechanical stress during soldering cycles. If the plating process is not perfectly controlled, voids may form at the interface between the via and the target pad. These voids can lead to intermittent connections or complete open circuits under thermal cycling.
Signal Integrity
The tiny physical footprint of these structures minimizes parasitic capacitance and inductance. This reduction in parasitics is critical for high-speed signals where traditional vias would act as stubs and cause signal reflections. By reducing the size of the transition, the design achieves much cleaner transmission lines and improved impedance matching.
This performance boost is essential for circuits operating at gigahertz frequencies.