Enhancing Photoresist Adhesion (2)
Back to InnerlayersCO-Bra Etch® Cu-Prep IICu-Prep IIICO-Bra Etch®
Product Description
The CO-BRA ETCH® process is a hydrogen peroxide/sulfuric acid microetchant which provides an efficient, stable cleaning and etching process for printed circuit boards. It can be used in spray or immersion.The CO-BRA ETCH® process is used in precleaning and etching of printed circuit boards prior to the various plating and processing steps. The process may be used as a direct substitute for ammonium and sodium persulfates, thus eliminating the disposal problem associated with the frequent dumping of these spent solutions.
The etch rate of the CO-BRA ETCH® solution is controlled by proper selection of CO-BRA ETCH® Replenisher concentration and temperature. The etch rate is consistent regardless of copper concentration within the normal operating limits.
The copper removed from the board by etching can be recovered from the CO-BRA ETCH® solution in the form of copper sulfate pentahydrate by using a continuous recovery system. This feature allows the CO-BRA ETCH® solution to be replenished and used indefinitely without dumping. Consult Electrochemicals for specific recommendations on recovery systems. Alternatively, the CO-BRA ETCH® solution can be dumped when the copper concentration reached 52.5 - 60 g/L (7 to 8 ounces per gallon).
Applications of the CO-BRA ETCH® process include:
- Microetching of innerlayers prior to application of photoresist
- Microetching of innerlayers prior to oxide coating
- Microetching of panels prior to electroless copper deposition
- Microetching of panels prior to electroplating
- Microetching of panels prior to solder mask application
Solution makup
| Copper Sulfate* | 15 g/L |
| Sulfuric Acid (Electrolytic grade) | 18% by volume |
| CO-BRA ETCH® Make Up** | 7% by volume |
| CO-BRA ETCH® Replenisher | 3% by volume |
| Water | Balance |
* When using equipment containing stainless steel parts at least 15 g/L of copper sulfate is required to prevent attack on the stainless steel.
** For spray applications CO-BRA ETCH® Make Up should be used at 3% rather than 7% to reduce the amount of foaming that will occur.
Operating condiitions
| Nominal | Range | |
| CO-BRA ETCH® Replenisher (% v/v) | 3 | 1 - 10 |
| Sulfuric Acid (% v/v) | 18 | 10 - 20 |
| Copper | 20 g/L (2.7 oz/gal) |
4 - 60 g/L (0.5 - 8 oz/gal) |
| Temperature | 43°C (110°F) |
32 - 49°C (90 - 120°F) |
| Dwell Time (sec.) | 20 | 10 - 60 |
| Total Etch Amount | 1.25 m (50 min) |
0.25 - 2.5 m (10 - 100 min) |
Cu-Prep II
Product Description
Cu-Prep II is a powdered product designed specifically to promote superior topography on copper substrates. Normal applications include pre-clean prior to photoresist or solder mask lamination pre-clean prior to electroless copper deposition, or pre-clean prior to oxide treatment.It has the benefits of:
- No ammonia for ease of waste treatment
- High copper holding capacity
- Chemically stable for long solution life
Solution makup
| Component | Concentration |
| Cu-Prep II | 75 g/L |
| Sulfuric Acid (electrolytic grade) | 2 % by volume |
| Copper Sulfate* | 15 g/L |
| Deionized Water | Balance |
Cu-Prep III
Product Description
Cu-Prep III is a powdered product designed specifically to promote superior topography on copper substrates. Normal applications include pre-clean prior to photoresist or solder mask lamination pre-clean prior to electroless copper deposition, or pre-clean prior to oxide treatment.It has the benefits of:
- No ammonia for ease of waste treatment
- High copper holding capacity
- Chemically stable for long solution life
Solution makup
| Component | Concentration |
| Cu-Prep III | 75 g/L |
| Sulfuric Acid (electrolytic grade) | 2 % by volume |
| Copper Sulfate* | 15 g/L |
| Deionized Water | Balance |
