Different Techniques for Plating
The hole-wall will obtain electro-less copper as well as about 0.025 mm (0.001 inch) of electroplated copper on through-hole PCBs that are plated. External lines will obtain about 0.025 mm (0.001 inch) of copper plating, using copper electroplating methodology, on top of the initial 0.5 or 1.0 ounces of copper foil that already exists.Depending on the requirements that must be adhered before or after the solder mask, all bare circuit elements must be protected by the following approved list of finishes:
Immersion Silver
- Usual coating thickness: 0.20 µm (0.00007 in) to 0.50 µm (0.0002 in)
- Superior ability for soldering
- Superior surface coplanarity
- Superior way to obtain uniform hole sizes
- Good for using in fine-pitch part technology
- Good for surface contrast – assembly vision ability
- PCB is not subjected to thermal shock (as with HASL)
- Good for “Pb Free” soldering
- Usual thickness: 0.7 µm (0.00003”) to 1.3 µm (0.00005”) gold (99.7%) over 5.0 µm (0.0002”) nickel or 0.2 µm (0.000008”) to 0.3 µm (0.00001”) gold (99.7%) over 5.0 µm (0.0002”) nickel for a solderable surface
- Very good for corrosion resistance
- Rated at 130-220 Knoop hardness
- Very good wear resistance
- Excellent for surface rotary switches, on-off contacts, and edge connectors
- Very good shelf life
- Usual thickness: 0.7 µm (0.00003 in) to 1.3 µm (0.00005 in) gold (99.9 percent) over 5.0 µm (0.0002 in) nickel
- Very good corrosion resistance
- Below 90 Knoop hardness
- Well suited for pressure contacts and aluminum or gold-wire bonding
- Average wear resistance
- Very good shelf life
- Usual thickness is 0.08 µm or 0.000003 inch to 0.2 µm or 0.000008 inch gold over 0.5 µm or 0.0002 inch nickel
- Superior resistance from corrosion
- Adequate for aluminum wire bonding
- Very Good for the use of fine pitch technology
- Superior ability for soldering
- Very good shelf life
- Usual coating thickness is 0.8 µm (0.000003 in) to 5 µm (0.0002 in); dependent upon the design
- Very good ability for soldering
- 0.635 mm (0.025 in) surface mount pitch or greater ability
- 0.75mm (0.030 in) is the minimum board thickness ability
- Adequate shelf life
- Usual coating thickness: 0.2 µm (0.000008 in) – 0.5 µm (0.0002 in)
- Good ability for soldering
- Very well suited for surface coplanarity and uniformity of the size of the hole
- Very good for fine-pitch technology
- Better surface contrast – capability for assembly vision
- PCB does not experience thermal shock (as with HASL)
- Adequate shelf life (1 year)
- Usual thickness is 7.6 µm (0.0003 in) Tin above 12.7 µm (0.0005 in) of nickel
- Surface can be soldered
- Adequate life on shelf
Related Articles:
- Full Body and Selective PCB Hard Gold Plating
- Solder Tinned Pads vs Gold Plated Pads - The Importance of Selecting the Proper Surface Finish
- ENIG vs HASL : Different surface finish techniques
- Best Practices for Plated Slots
- Immersion Silver
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