Specialized Etching and Plating methods for Heavy Cu Fabrication
There are three primary methods to create Heavy Copper PCB designs.
1. Etch-Down
This is the traditional methodology to create printed circuit boards. Essentially, in the case of a PTH design, we start with a base copper 1 ounce less than the desired finished copper weight and plate up to the target copper weight. We then would etch down the base copper to the base laminate in order to create the design features (circuits, pads, etc.). The challenge with heavy copper designs is that most fabricators and their equipment are capable of only standard copper weights (2 ounce or less).
2. Plate-Up:
Instead of plating the typical 1 ounce to the base copper of surface features to achieve target copper weight, this methodology requires starting with a copper weight significantly less than the target. Then by repeating a series of process steps of image through plating you achieve the target copper weight.
3. Hybrid:
This is the most effective method of combining digital and power requirements. Basically the designer buries the heavy copper features on the inner layers and utilizes standard copper weights on the outer layers. This enables the use of finer pitch components while at the same time addressing high power requirements.
| Etch-down | Plate-up | Hybrid | |
| Cost | Medium |
High | Standard |
| Process flow | Standard | Complex | Standard |
| Min line / space | Large | Medium | Standard |
| Materials | 6oz. max / up to 20oz. (non UL) | max recommended 3oz. | 6oz. max / up to 20oz. (non UL) |
| Supplier availability | Limited | Limited | Standard |
| Solder mask | Trace fill ink; spray method | Standard | Standard |
| DFM rules | Standard | Variable | Standard |
| Failure modes | Standard | HIgh | Standard |
| Cu weight variation | Standard | Due to plating variation | Standard |
| Lead times | Standard | Long | Standard |
| Level sidewalls | Yes | No | Yes |
| SMT compatible | Dependant on Cu Weight | Yes | Yes |