The following are recommended rules and suggested conditions for manufacturing substrate materials with Direct Bonded Copper.
COPPER THICKNESS RANGE: As thin as .0035” {.089mm} As thick as .012” {.305mm} Standards are: 5 Mil 8 Mil 10 Mil and 12 Mil
ETCH FACTORS: Due to the copper thickness, etch factors must be considered. The chemical machining of the copper removes material from side to side as well as from top to bottom and therefore we must consider ‘etch factors’. This can be calculated by considering one half the copper thickness per side as an etch factor. ie, 10 Mil copper has a 5 Mil etch factor per side.
LINE WIDTH AND SPACE TOLERANCES: Both line width and space between lines have minimum’s. The minimum line width is 3 X copper thickness and the minimum space between lines is 3 X copper thickness. ie, 5 Mil copper must have at least a 15 Mil wide line with 15 Mil wide spacing between lines and with 10 Mil copper must have at least a 30 Mil wide line with 30 Mil spacing between lines.
COPPER ETCHING TOLERANCES: Tolerances on etched copper are ± 50% of copper thickness. ie, 6 Mil copper has a tolerance of ± .003” and 10 Mil copper has a tolerance of ± .005”.
EDGE PULL BACK: Both the front side and the back side of the circuit should have a pull back from the ceramic edges. That pullback should be at least 5 Mils. In many instances, it may be desirable to have the copper pulled back from the edges by 20 Mils or more due to the ability of the copper to accept large current values as well as the ability to dissipate heat.
THICKNESS AND SIZE:
Thickness Range from .010” (.254mm) to .100” (2.54mm)
Size from as small as ¼ X ¼ to as large as 4.0” X 4.0”
STANDARD SIZES OF BLANK SUBSTRATES: Alumina: From 1” X 1” to 4” X 4” BeO: 2.06” X 2.06” or 2.2” X 1.8” or 2.3” X 2.9” or 3.0” X 3.0” or 4.0” X 4.0” AlN*: From 1” X 1” to 4” X 4
