Text version of the page

â–¼

Circuit Design Recommendations

This section will address circuit design with respect to etching,surface finishing and mechanical fabrication processes; such as holes, flatness, singulation and tolerances.Fabrication of Thermal Clad is similar to traditional FR-4 circuitboards with regard to wet processing operations. However, secondary mechanical operations are unique, therefore consideration to specific design recommendations are critical to insure manufacture of reliable cost effective Thermal Clad circuits. This section will address design recommendations for circuit image, soldermask, legend screen, and mechanical fabrication. Additional consideration for trace widths, spacing and clearances may be required for electrical integrity based in application voltage (see electrical design considerations pages 18-19). Cross Section View Planned View
Note: Use of a soldermask is mandatory. Bold numbers within these drawings reference the adjacent table.

Part Singulation Methods

Milling/Routing/Drilling Flatness

Processes typically selected for prototype or low volumeproductionwith complex geometries. Unique designs with selectiveareas of removed dielectric may require milling/routing processes. Milling operations require fixturing. Milling/routing is typically not cost effective for moderate to high volume applications. Part design as well as the manufacturing process affects flatnessof a Thermal Clad board. There is also an effect from the differentialthermal coefficient of expansion (TCE) between the circuit and the base layer. That effect is determined by the base plate materialselection,ratio of copper foil to base plate thickness and coppercircuit pattern design.For Thermal Clad, panel or part, there is always some bowcaused by the difference in CTE between the circuit layer and the substrate. Flatness is most evident when the substrate metal is aluminumand the circuit layer is copper. Generally, if the thicknessof the copper layer is less than 10% of the substrate thickness, the aluminum will be mechanically dominant. Constructions with more circuit copper than 10% of the substrate thickness can exhibit a bow.

V-Scoring

V-scoring is a viable process selection for both low and highvolume production by taking advantage of material utilization. V-scoring is also a preferred process for prototypes with rectangular geometries with the benefit of no tooling costs. Holes can be drilled, or punched prior to scoring.

Blanking

Blanking is one of the most cost effective process for moderateto high volume applications. Blank tooling can accommodate complexpart geometries, as well as pierce internal holes. 16