Land patterns are based on the IPC-7351A SMT land pattern standards and take various parameters into account:
1. Compensation variables for fabrication and assembly processes
2. Preset operating environments or user defined goals for land pattern toe, heel and side protrusions
3. Solder joint analysis
4. DRC protection from overlapping lands
The IPC-7351A LP standards allow for Manufacturing Tolerances that determine the pad size, Placement Courtyard Tolerance, PAD Width Round-off, and Component Tolerance. Also accounted for is Pick & Place Zero Component Rotation for accurate assembly data. The JEDEC JEP95 publication and the EIA / ANSI 481 specification for tape and reel packaging was used to determine the exact component zero rotation on the assembly tape and reel or tube so that CAD library parts placed in the same zero rotation provide accurate assembly data. Density Level A: Maximum (Most) Land Protrusion
For low-density product applications, the 'maximum' land pattern condition has been developed to accommodate wave or flow solder of leadless chip devices and leaded gull- wing devices. The geometry for these devices, as well as inward and “J”-formed lead contact device families, may provide a wider process window for reflow solder processes as well. Density Level B: Median (Nominal) Land Protrusion
Products with a moderate level of component density may use the 'median' land pattern geometry. The median land patterns for all device families will provide a robust solder attachment condition for reflow solder processes and should provide a condition suitable for wave or reflow soldering of leadless chip and leaded gull-wing type devices. Density Level C: Minimum (Least) Land Protrusion
High component density typical of portable and hand-held product applications may consider the 'minimum' land pattern geometry variation. Selection of the minimum land pattern geometry may not be suitable for all product use categories. Cadcom can also calculate for impedance in the following parameters: 1. Asymetric Stripline 2. Differential Pair microstrip 3. Differential stripline 4. Embedded microstrip. We also calculate for current through given track width using the formula: I=kT0.44A0.725 | 
