Acid copper plating pulse processes
Back to Plating in 3DElectro-Brite PC-695
Acid Copper Plating ProcessElectro-Brite PC-626 Acid Copper Plating
Process - A New product for high aspect ratio high density designs DC
PlatingElectro-Brite PC-695 Acid Copper Plating Process
Product Description
Electro-Brite PC-695 is an acid copper plating additive system that has been specifically optimized for use with pulse periodic reverse rectification on a continual production basis.The process produces a fine-grained, ductile deposit with excellent distribution characteristics, and is maintained with two components. The combination of PC-695 and a periodic reverse pulse plating rectifier can significantly shorten plating times while maintaining excellent distribution ratios.
Solution makeup
| Copper Sulfate Pentahydrate | 70 g/L |
| Sulfuric Acid | 12.5% by volume (225 g/L H2SO4) |
| PC-695 Carrier | 1.0% by vol. |
| PC-695 Replenisher | 0.04% by vol. |
| Deionized Water | Balance |
| Chloride | 80 ppm |
*Note: 2.2 mL of concentrated hydrochloric acid added to 100 L of bath will raise the chloride concentration by 10 ppm (10 mL per 100 gal adds 12 ppm of chloride).
Mixing Instructions
Fill to half of final working volume with deionized water.With mixing, add the required amount of copper sulfate and dissolve.
With heavy mixing, slowly add the required amount of sulfuric acid. The addition of sulfuric acid produces a considerable amount of heat. If PVC structures are present, monitor the temperature of the solution and do not allow it to exceed 49°C (120°F).
Cool, with mixing, to 29°C (85°F).
With mixing, add the required amounts of PC-695 Carrier and PC-695 Replenisher.
Fill to final volume with deionized water and mix.
Check the chloride content of the bath and add sufficient hydrochloric acid to raise the chloride to approximately 80 ppm.
Electrolyze (dummy plate) the bath for 3 hours at 20 ASF (2 ASD) while maintaining the brightener concentration by CVS, CPVS or dilution Hull cell (the feed rate of PC-695 Replenisher should be about 0.3 to 0.8 ml/amp.hr, however, the initial feed rate for the first day may be higher). The PC-695 Carrier feed rate should be about 0.25 to 0.5 ml/amp.hr. The pulse waveform should set at 40 msec forward; 2.3 msec reverse and a 2.0 to 1 reverse current ratio. Plate a test panel and obtain cross-section results to be sure the optimum performance is obtained before starting production. Some plating tank or board designs may require special waveforms or brightener concentrations in order to obtain optimum results.
Operating conditions
| Nominal | Range | |
| Copper Sulfate | 70 g/L (9.3 oz/gal) |
65 -75 g/L (8.7 - 10 oz/gal) |
| Sulfuric Acid | 225 g/L (12.5% by vol.) |
215 - 235 g/L (12 - 13% by vol.) |
| Chloride | 80 ppm | 70 - 90 ppm |
| PC-695 Carrier | 1% by vol. | 0.5 - 2.0% by vol. |
| PC-695 Replenisher | 0.04% by vol. | 0.03% - 0.05% by vol. |
| Temperature | 29°C (85°F) |
27 - 32°C (80 - 90°F) |
| Forward Cathode Current Density | 30 ASF (3 ASD) |
20 - 50 ASF (2 - 5 ASD) |
| Pulse cycle | Forward time: 40 milliseconds Reverse time: 2.3 milliseconds Reverse CD Ratio 2.0 to 1 (Pulse cycle can vary depending on plating operation.) |
| Anode Current Density | 10 - 35 ASF (1-3.5 ASD) for forward current. Note: Higher anode current densities can lead to passivation of the anode surface |
| Agitation | Air or eductors (eductors preferred) and cathode rod |
| Filtration | Continuous, 2 - 3 turnovers per hr (1 micron polypropylene filter is recommended) |
| Anodes | Phosphorized copper (0.03% - 0.08% phosphorous) |
| Anode Baskets | Titanium (square baskets with nuggets is recommended) |
| Anode Hooks | Titanium |
| Anode bags | Polypropylene (cotton and other cellulose based materials are unacceptable) |
Bath operation and maintenance
The copper, sulfuric acid, and chloride content of the acid copper plating solution are analyzed using the analytical procedures that are included in this data sheet. The PC-695 Carrier and PC-695 Replenisher concentrations are controlled by proprietary CPVS and or CVS procedures (as well as specially prepared Hull cell methods) which are not included in this data sheet. Please refer to the separate control procedure bulletins for these methods or consult your technical service representative.All new anode bags and filters should be leached before use in an acid copper plating bath. The materials should be leached in hot water (43° - 71°C, 110° - 160°F) with changes of water until fresh leach water no longer foams. The initial leach can be augmented by the addition of 3% sulfuric acid.
The anode current density should not exceed 35 ASF (3.5 ASD) in general operation. Excessive anode current density can lead to anode polarization and poor deposit distribution and structure.
Anode to cathode distance spacing is also important in the general operation of an acid copper plating bath. An anode to cathode distance of 20 - 30 cm (8 to 12 inches) is recommended to insure a more uniform distribution of the deposit.
It should be noted that anode and cathode placement, agitation, copper concentration, temperature, electrical connection and circuit configurations can affect distribution and usable current density range. More details of these effects can be found in the attached troubleshooting guide.
The optimum temperature for most situations is 29°C (85°F) with a range of 27 - 32°C (80 - 90°F). Low temperatures may cause burning.
Function of bath components
Copper SulfateCopper sulfate provides copper ions for the deposition process. It should be maintained within the specified limits of 65 - 75 g/L. Higher levels give no advantage at 30 ASF but may help increase leveling at higher current densities. Lower concentrations will reduce maximum operating current density but can give improved metal distribution.
Sulfuric Acid
Sulfuric acid provides solution conductivity. It should be maintained between 12% - 13% by volume. Higher concentrations may lead to anode polarization. Low concentrations may degrade deposit distribution.
Chloride Content
Chloride supports the action of the PC-695 Replenisher and ensures an even dissolution of the anodes. A low concentration will lead to a streaky or nodular deposits. A high concentration will cause anode polarization with a characteristic white anode film.
The consumption of chloride will be higher during the filming of new anodes and it may be necessary to maintain the concentration by additions of hydrochloric acid.
PC-695 Replenisher
PC-695 Replenisher is responsible for the grain refining of the deposit and is usually replenished at approximately 0.2 - 0.5mL/amp.hr. A low concentration will cause rough matte deposits. High concentrations may cause loss of throwing power and leveling.
PC-695 Carrier
PC-695 Carrier is responsible for the wetting action and throwing power of the solution and it is necessary for a minimum quantity to be present to ensure that the PC-695 Replenisher works optimally. Under normal conditions a replenishment rate of 0.25 to 0.5 mL per amp hr is sufficient.
Electro-Brite PC-626 Acid Copper Plating Process
New product for high aspect ratio high density designs DC
Plating
Product Description
Electro-Brite PC-626 Acid Copper Plating Process is an outstanding copper sulfate plating system designed to produce a bright, ductile copper deposit particularly suited for the printed circuit industry.PC-626 does not contain any dye. PC-626 Acid Copper requires a single additive for replenishment and provides several advantages:
| - | PC-626 produces leveling by the action of its brightener and carrier components, without the need for additional leveler components. This eliminates the problem of controlling a separate leveler and the degradation of the physical properties and distribution of the deposit that occurs if there is a build-up of a leveler component. |
| - | PC-626 is very economical. The average replenishment rate is 0.2 mL per ampere hour, but various operating conditions can cause an addition rate as low as 0.1 mL per ampere hour to as high as 0.4 mL per ampere hour. |
| - | PC-626 is designed to produce a bright ductile copper deposit particularly suited for the printed circuit board industry. Good ductility is necessary to withstand the forces created by the difference in coefficient of thermal expansion between the laminate and the copper. |
| - | The process produces a fine grained amorphous copper deposit. This fine grained structure is the desired structure for a ductile deposit. The copper deposit produced by PC-626 will pass the most rigorous thermal stress and shock tests. |
| - | PC-626 is extremely stable in the bath, thus eliminating the need for frequent purification to remove breakdown products which cause excessive stress and dullness. |
Nominal Deposit Characteristics
When properly plated, samples are tested per ASTM specification:
| Electrical Conductivity | 0.59 micro-mho/cm |
| Elongation | 15 - 25% |
| Internal Stress | 750 - 1500 psi |
| Density | 9.0 g/cc |
| Tensile Strength | 42,000 to 53,000 psi |
| Solderability | Excellent |
| Microscopic Structure | Fine Grained Equiaxed |
Solution makeup
| Copper Sulfate | 75 g/L |
| Sulfuric Acid | 10% by volume |
| Hydrochloric Acid | 60 ppm of chloride* |
| PC-626 | 0.15% by vol. |
| Acid Copper Carrier | 1.0% by vol. |
| Deionized Water | balance |
*Note: 2.2 mL of concentrated hydrochloric acid added to 100 L of bath will raise the chloride concentration by 10 ppm (10 mL per 100 gal adds 12 ppm of chloride).
Electrolyze (dummy plate) the bath at about ½ of normal operating current density for 1-4 hours. After electrolysis, the chloride and PC-626 concentrations should be checked. A Hull cell and/or Cyclic Voltammetric Stripping (CVS) analysis can be used to determine the concentration of PC-626. The initial formation of the anode film can consume larger than normal amounts of chloride and PC-626.
Operating conditions
| Nominal | Range | |
| Copper Sulfate | 75 g/L(10 oz/gal) | 60 -120 g/L(8 - 16 oz/gal) |
| Sulfuric Acid | 184 g/L(10% v/v) | 166 - 258 g/L(9 - 14% v/v) |
| Chloride | 60 ppm | 40 - 90 ppm |
| PC-626 | 0.15% v/v | 0.08 - 0.30% v/v |
| Acid Copper Carrier | 1.5% v/v | 0.5% - 4% v/v |
| Temperature | 24°C(75°F) | 21 - 32°C(70 - 90°F) |
| Cathode Current Density | 18 ASF(1.9 ASD) | 12 - 30 ASF(1.3 - 3.2 ASD) |
| Agitation | Air, pumped solution and cathode rod agitation are applicable (compressed air must be avoided) |
| Filtration | Continuous (1 - 5 micron filter is recommended) |
| Anodes | Phosphorized copper (0.03% - 0.08% phosphorous slabor slug anodes ) |
| Anode Baskets(if used) | Titanium |
| Anode Hooks | Titanium |
| Anode bags | Polypropylene (cotton and other cellulose based materials are unacceptable) |
| Anode Current Density | 10 - 35 ASF(1.1 - 3.8 ASD) |
Note: Lower anode current densities tend to increase brightener consumption and higher anode current densities can lead to passivation of the anode surface.
Important considerations
Plating thickness is dependent upon current density and plating time. For acid copper plating 17.8 ampere hours or 1068 ampere minutes are required to obtain 1 mil (25 micron) of plated thickness. The relationship is illustrated in the following calculation:| Plating thickness (mils) = | [time (min.) x current density (ASF)] |
| /[ 1068 ampere minutes/mil] |
Actual thickness in plated holes will depend upon board geometry and the throwing power of the plating bath. Current density, tank geometry, solution movement and bath parameters all influence the throwing power of the plating bath.
