CO-BRA Bond ® The Oxide Alternative
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®CO-BRA Bond ®
Product Description
The CO-BRA BOND® Process is a modified peroxide/sulfuric acid process designed to prepare copper surfaces prior to multilayer lamination of printed wiring boards.The CO-BRA BOND® solution promotes the formation of a brown copper-organic coating, which enhances the surface for resin bonding. This structure improves bond strength over conventional oxide coatings, especially on high Tg, high performance materials.
The CO-BRA BOND® process is a much shorter process than a standard oxide process and operates at a lower temperature.
Solution makup
CO-BRA BOND® Predip:| CO-BRA BOND® Replenisher A | 1.5% by volume |
| CO-BRA BOND® Oxidizer - 50 | 2.0% by volume |
| OR | |
| CO-BRA BOND® Oxidizer - 35 | 2.9% by volume |
| Deionized Water | Balance |
CO-BRA BOND®:
| Concentrated Sulfuric Acid | 5% by Volume |
| CO-BRA BOND® Replenisher A | 5% by volume |
| CO-BRA BOND® Replenisher B | 5% by Volume |
| CO-BRA BOND® Oxidizer - 50 | 2.8% by volume |
| OR | |
| CO-BRA BOND® Oxidizer - 35 | 4.0% by volume |
| Deionized Water | Balance |
Operating condiitions
| Nominal | Range | |
| Predip | ||
| CO-BRA BOND® Oxidizer - 50 (% v/v) | 2.0 | 1.5 - 2.5 |
| OR | ||
| CO-BRA BOND® Oxidizer - 35% (%v/v) | 2.9 | 2.1 - 3.6 |
| CO-BRA BOND® Replenisher A (% v/v) | 1.5 | 1.0 - 2.0 |
| Sulfuric Acid (g/L) | 1.35 g/L | .9 - 1.8 |
| Filtration: | 3 - 5 turnovers per hour during operation using a 1 - 5 micron polypropylene wound filter. |
| Agitation: | Filtration pump and mechanical movement. |
| CO-BRA BOND® | ||
| CO-BRA BOND® Oxidizer - 50 (% v/v) | 2.8 | 2.0 - 4.0 |
| OR | ||
| CO-BRA BOND® Oxidizer - 35% (%v/v) | 4.0 | 2.9 - 5.7 |
| CO-BRA BOND® Replenisher A (% v/v) | 5.0 | 2.9 - 5.7 |
| CO-BRA BOND® Replenisher B (% v/v) | 5.0 | 4.0 - 7.0 |
| Sulfuric Acid (% v/v) | 5.0 | 4.5 - 7.0 |
| Copper Metal (g/L) | 15 - 20 | 2 - 20 |
| Temperature | 38°C (100°F) |
35 - 41°C (95 - 105°F) |
| Dwell Time (sec.) vertical | 60 | 50 - 70 |
| Dwell Time (sec.) horizontal | 40 | 30 - 50 |
| Total Etch Amount | 1.78 µ (70 µin) |
1 - 2.5 µ (40 - 100 µin) |
| Filtration: | 3 - 5 turnovers per hour during operation using a 1 - 5 micron polypropylene wound filter. |
| Agitation: | Non-compressed air. Single row of 1/16 inch holes every 1.5 inches apart in a 1 inch pipe (pointing down). Each leg should be spaced a maximum of 6 inches apart, perpendicular to innerlayers. Use a separate feed pipe for every two sparger legs. |
Recommended process cycle
| 1. | CO-BRA BOND® Alkaline Cleaner |
| 2. | Deionized water rinse |
| 3. | CO-BRA BOND® Pre-Dip |
| 4. | CO-BRA BOND® |
| 5. | Water Rinse |
| 6. | Dry |
Bath operation and maintenance
The CO-BRA BOND® Process is controlled similar to other peroxide/sulfuric etchants. CO-BRA BOND® Oxidizer (peroxide), sulfuric acid and copper are monitored and controlled via simple titration.CO-BRA BOND® Oxidizer, CO-BRA BOND® Replenisher A, CO-BRA BOND® Replenisher B and sulfuric acid are consumed in proportion to the amount of copper removed. For etching 1 surface square foot of laminate (50% copper surface area) the amount consumed will be:
| CO-BRA BOND® Oxidizer - 50 | 1.8 mL |
| OR | |
| CO-BRA BOND® Oxidizer - 35 | 2.6 mL |
| CO-BRA BOND® Replenisher A | 1.8 mL |
| CO-BRA BOND® Replenisher B | 2.5 mL |
| Sulfuric Acid | 2.75 mL |
As work is processed the copper concentration will continue to increase. The copper level should be kept below 20 g/L to provide consistent etch rate.
The amount of copper etched should be monitored on a regular basis using cleaned copper clad laminate.
The amount etched can be calculated as follows:
Amount etched (µin) = weight loss (g)/(0.0212 x surface area (sq. ft.))
Amount etched (µ) = amount etched (µin)/39.4
The etch rate is affected by the CO-BRA BOND® Oxidizer concentration as shown in Graph 1.
Sulphuric Acid specifications
Sulfuric acid used with the Electrochemicals CO-BRA BOND® process should be electrolytic grade.| Sulfuric Acid (as H2SO4) | 93.19% min. by wt. |
| Specific Gravity at 15oC (60oF) | 1.835 - 1.836 |
Contaminants should not exceed the below listed maximums:
| Hydrochloric Acid (as HCl) | 5 ppm |
| Nitrate (as NO3) | 5 ppm |
| Iron (as Fe) | 42 ppm |
| Antimony (as Sb) | 1 ppm |
| Selenium (as Se) | 20 ppm |
| Manganese (as Mn) | 0.2 ppm |
| Nickel (as Ni) | 1 ppm |
Equipment
Tanks, tank linings, pumps, and other handling equipment should be suitable for use with 8% v/v sulfuric acid and 2 - 4% v/v hydrogen peroxide.Most 300 Series Stainless Steel equipment may be used to handle the CO-BRA BOND® solution, provided the bath contains a minimum 3.85 g/l of metallic copper (15 g/l CuSO4 5H2O). Passivation of newly welded stainless steel equipment with nitric acid is recommended.
The mixing procedure outlined in this bulletin is recommended to minimize attack on stainless steel.
Tanks
Reinforced fiberglass (oxidation resistant resin), polyethylene, polypropylene, stainless steel (300 Series), etc.
Pumps (Circulation and Transfer)
Stainless Steel (300 Series), PVC (unplasticized), etc. The supplier should approve magnetic-driven plastic pumps.
