snowboard

From this relatively simple test vehicle we will be able to begin the process of establishing quantitative values for power dissipation and power density of the resistor design as a function of the current and the board construction. Later, we will work our way into more complex constructions.

The requirements of temperature and time for pre-heat depend on the board construction, age and exposure to the atmosphere.

The reduced effective dielectric constant also yields a thickness reduction for FR-4 boards, thus allowing greater overall layer density, thinner board construction and reduced weight.

Embedded in fabrication planning is calculating panel size, checking layer stackup information, reviewing expected yields, reviewing board construction and verifying impedance control calculations.

The design of resistors depends on the current, which in turn determines their power requirements and the size and shape, all of which relates back to the board construction.

Meanwhile, mainstream low frequency circuit manufacturers were using glass-epoxy FR-4 material systems consisting of a laminate core material and a B-stage of the same resin system to achieve homogeneous multilayer circuit board construction in a flexible, cost-effective manner.

The final step is converting the resulting cross-sectional area to the final trace width, based on the thickness of copper used in the board construction. This step should not be confused with the modification based on copper thickness to account for varying surface area.

* Affected by board construction; PCBs with more resin, less copper and lower Tg materials tend to show more expansion in the Z-axis.

FIGURE 2 is a detail of a standard printed circuit board construction.

REFLOW * Excessive peak temperatures * Incorrect profiles/rework MATERIAL * Incorrect material choice, Tg or compatibility * Breakdown of the dielectric material/quality LAMINATION FACTORS * Incomplete lamination * Excessive lamination temperatures * Excessive moisture * Incorrect Tg achieved BOARD CONSTRUCTION / DESIGN FACTORS * Inner layer build/copper distribution * Pre-preg build up/coarse glass interface/resin starvation * Hole cluster density COPPER: DIELECTRIC BOND * Inadequate or incomplete oxide coverage * Contamination of oxide or core dielectric * Breakdown of oxide coating TABLE 3.