- Select the Thermal option from the Analyze menu (see Figure 1).
- The Thermal graphical interface appears (see Figure 2). The active part name appears in the upper right. The right side of the screen displays the temperature scale. In the center of the screen is a schematic representation of the package, covered with a grid overlay dividing the package into nodes for a finite difference analysis. The interface also contains these three options.
- Boundary enables you to set boundary conditions for the top, sides, and bottom of each package grid node and to specify a conduction-only or a conduction/convection analysis.
- Parameter enables you to vary the number of analysis iterations, convergence values, relaxation factors, number of x and y nodes, and the range of the temperature scale.
- Analyze performs the thermal analysis once all parameters have been defined.
- Top, Bottom, and Sides enable you to set the boundary conditions (i.e. set temperatures) for the boundary nodes.
- Fill enables you to set a single temperature at a boundary.
- Clear clears all top, bottom, or side boundary conditions.
- Define enables you to switch from a conduction-only analysis to a conduction/convection analysis.
- Select the Top command from the Boundary option header menu. The header at the top of the diagram changes to "Set Top Conditions."
- Select a boundary condition temperature in the temperature legend.
- Select a node you want to apply the temperature to. It turns the color assigned to that temperature in the temperature legend (see Figure 4).
- Repeat Step 3 until you have applied the temperature to the appropriate boundary nodes.
- Repeat Steps 1-4 until all nodes are colored.
- Select the Top command from the Boundary option header menu. A view of the top of the package appears. If boundary condition temperatures have been applied, the grid will appear in color.
- Select the Clear command from the Boundary option header menu (see Figure 6). The grid will revert to a clear format i.e., temperature assignments of the top of the package will be canceled. You can now assign new temperatures.
- Select the Define command from the Boundary option. A window with three buttons appears (see Figure 7).
- If you want a conduction-only analysis, select the conDuct button. For a conduction/convection analysis, select the conVect button. Select the Cancel button to cancel the operation.
- Select the Top command in the Boundary option header menu. A Convection Parameters window appears. The blue highlighter bar is over the Ambient Temperature field (see Figure 9). The ambient temperature is the temperature of the air surrounding the package and is used to determine the air properties and temperatures used for the natural convection boundary conditions on the top and bottom planar surfaces of the package model. Its range is -55 to 125?C.
- Type an ambient temperature value.
- Move the highlight bar to the Ave. H (average convection coefficient for the lid-atmosphere interface) field and type a value.
- Select the OK button to accept the values. Select the Cancel button to cancel.
- If you accept the new values, you return to the Top command. Assign boundary condition temperatures to the nodes.
The Thermal Analysis determines the thermal profile of microelectronic packages. A finite difference method is used to make the calculations. As with any analysis of this kind, the first step is to define the problem and set up the boundary conditions. CADMP-II enables you to perform conduction-only and conduction/convection analysis. When performing conduction-only analysis, CADMP-II assumes that heat transfer from the package occurs purely due to conduction from the die(s) to the package case. When performing conduction/convection analysis, convection heat transfer from the top of the package and the atmosphere is also included by incorporating a user-specified package-to-air convective heat transfer coefficient. The bottom and side boundaries of the package can be assigned temperatures, or may be insulated.
The results of the analysis are displayed as color temperature contours across the surface of the package layers. In order to see every level of the package, parts can be removed to expose the structures below. For instance, the lid can be removed in order to view the underlying dies and substrate. Crossviews and zooms in both directions are also available.
7.1.1 The Thermal Graphical Interface
Use the Boundary option to set node boundary conditions (i.e., node temperatures). You must set temperatures for the package top, bottom, and sides in order to perform the thermal analysis. This is done by specifying the temperature of each node. Node size is defined in the Parameter option (see Section 7.1.3).
The Boundary option contains six commands (see Figure 3):
To apply a single temperature to all Top nodes, select the Fill command from the Boundary menu after selecting the temperature from the temperature legend in Step 2. All Top nodes turn the color assigned to that temperature (see Figure 5).
Select the Bottom command and follow the procedures in Section 7.1.2.1 to apply temperatures to the bottom of the package.
Select the Side command and follow the procedures in Section 7.1.2.1 to apply temperatures to the sides of the package.
Use the Clear command to cancel application of boundary condition temperatures to the top, bottom, or sides of a package.
Use this same procedure to cancel application of boundary condition temperatures to the package bottom and sides.
The Define command enables you to choose between a conduction-only or a conduction/convection analysis.
If you selected conduction/convection analysis, proceed to Section 7.1.2.5.1.
7.1.2.5.1 Setting Up the Conduction/Convection Analysis
If you select a conduction/convection analysis, you must enter convection parameters as instructed below. All other options and commands are identical to those used by a conduction-only analysis. The Thermal graphical interface remains the same (see Figure 8).
When performing a conduction/convection thermal analysis, CADMP-II performs an analysis of the package side, and assumes heat transfer occurs by conduction to the package base and by natural convection to the atmosphere from the package.
