Prepping The Copper Laminate Surface:

Many people tend to over do this simple process to prepare the copper surface. All you need is one of those green/yellow "ScotchBrite" scrubbing pads, a drop of dishwashing soap and paper towels. Wet the green side of the pad and apply a drop or two of dishwashing soap. Lightly rub the copper surface in a circular motion covering the entire copper area to remove ozidation and other contaminants like fingerprints, etc.

Wash the board throughly under running tap water and dry with paper towels. It's that simple and does not require ANY further "cleaning"!

If you have a failed attempt at transferring a PCB image, simply wet a new paper towel with Acetone and wipe the toner image off, then go back and clean the board again with the ScotchBrite and a drop of soap. The trick to successfully removing toner and GreenTRF film is to ensure both the board and the paper are free from any moisture!

 

Why 1/2oz Copper? Isn't 1oz better?:

One ounce blank copper boards have always been a commercial standard whereas Mil-Spec has always been 2oz. Most everyone buys blank 1oz copper boards because that's just about all you ever see. These 1oz copper clad boards are absolute overkill for, dare to say, 99% of projects and prototypes made today for both thru-hole and SMT. Sure there are those power supplies and the like that need to push a ton of amps but that's the exception rather than the rule. By reducing the copper thickness right from the start, it's easy to be able to render very fine trace pitch. This has never been more important than now with the density of boards constantly going up driven by micro-processors and small SMT components.

An interesting fact we discovered years ago was that the big board houses that make those ump-teen layered super high-end commercial boards, having those incredibly fine traces amazingly cram packed together, is that they start with 1/8oz copper-laminated board (and sometimes less). The objective is to reduce "undercutting" to near zero!

Undercutting is when the etchant starts to eat sideways after it has gone below the layer of the etch resist mask. Since the etching process is working on both sides of a trace, it doesn't take long before the trace literally disappears!

Fine traces that are pushing .001" or less don't have to undercut but a fraction and the board is trashed. So, by using these extremely thin copper laminates, the etch is nearly instanteous. Being that the copper is so thin, it doesn't take much heat to vaporize a trace. You couldn't reflow solder to copper this thin so the board house have to "plate up" the entire board to either 1oz for commercial or 2oz for Mil-Spec before it makes it back to the customer.

Because we don't want to get involved with "plating", we took the middle of the road and standardized our system using 1/2oz copper. Undercutting automatically becomes half of that of 1oz copper which means you can now image down to an amazing .005" - plenty small enough for just about any applications imaging on single or double-sided boards. The bonding strength of 1/2oz by the way is the same as 1oz and there is no chance of vaporizing a trace with standard temperature controlled irons or even lifting a pad with multiple re-work sessions.

Under the LIBRARY menu section there is an interesting chart for determining just how much current a trace can handle for a given width using 1/2oz, 1oz or 2oz copper.

Up to this point we've only discussed the "weight" of copper. (As a point of reference, the term "weight" for circuit boards came from the method of meauring. If you make a 12" square pan and pour out 1 Troy ounce of liquid copper and it flows out before cooling, that would be the thickness of the copper!) It's not measured by actual micrometer thickness but it is about .001"... not much! So you can see how thin 1/8th oz would be.

Our system also uses the fiberglass base at .032". (One credit card thickness.) Again, the common board you see is double that at .064". (The actual number always varies a few thousands based on the manufacturer, but in general these are good numbers).

We happened to luck-out a bit here. The applicator device we endorse as the ideal tool for making boards can not pass boards much thincker than .032". Any thicker and the motor gets over-taxed and can stall. (You can however, use .064" boards with our system, you just have to "help" the board through the unit.) The other two good reasons to use .032" thick laminate is that you can easily cut the board with a standard paper cutter. The last reason is that we're generally trying to put more electronics into less space. By cutting down on the thickness of the board, we've make a significant space for SMT use.