It's hard to get real 1 oz copper, much less 2 oz. People start with
> 1/4 or 1/2 and plate it up, and they tend to quit too soon. One of my
> fab drawings says START WITH 2 OZ COPPER.
In this case my fab drawing said (in HUGE letters), "Board shall be
2oz finished copper." The fab house claims that they started with 1oz copper and plated up to 2oz. I have asked for them to provide in writing what they did. I am now wondering how to prove whether or not they complied with the requirement. I personally dont think it "feels" like a 2-oz copper board. The raised height just isnt what I was expecting....it seems very thin. What types of quality control rules do you use for determining what was actually delivered? I dont have an accurate depth gauge, but I suppose I could use calipers to measure the thickness of an area with no copper (only soldermask) and compare that to an area with full copper to determine the copper
+plating thickness....then determine what thickness 2oz copper should be.
A colleague told me that "Copper weight is given in oz / per sq foot.
1 oz =3D a minimum of 0.0012=94- 0.0014=94 thickness". So I suppose that
2oz finished would be 0.0024" - 0.0028" thick. Also, in a 2003 usenet archive post, Rene Tschaggelar offered these numbers (and I provided the translation to mils)...
1oz 35um 1.38mils
2oz 70um 2.76mils
3oz 105um 4.13mils
6oz 0.2mm 7.87mils
9oz 0.3mm 11.81mils
For my current situation, the PCB is measuring 0.062" thick in an area with no copper (only PCB and soldermask) and 0.065" in an area with copper on both sides. This implies 3mils of copper on top and bottom, so 1.5mils of copper on each side. I dont think this would qualify as
2oz finished copper, but now I have to convince the fab house to eat
1000 pcbs due to their fault...
(PS-My application only deals with automotive 12vdc and 10amps, but I am mostly concerned with adequate copper for heatsinking my D2PAKs because of a slooooowly switching Infineon half bridge driver running as fast as it can go).
Any insightful comments? Thank you! frenchy (Steve French)