Typical Precious-Metal Process Control

1. Clean and condition the copper surface; remove oils, oxides and residues.
2. Microetch to create a fresh, uniform copper surface, followed by thorough rinsing.
3. Activate the surface and deposit the specified nickel, palladium, silver or gold layers in the defined sequence.
4. Control bath condition, temperature, dwell time, loading and agitation; verify thickness and appearance.
5. Use clean final rinses and complete drying before inspection and packaging.

Immersion Tin — Reference Process Sequence

The supplied CSN Classic material describes the following general route:

• Cleaner: 10–15 vol%, 40–50°C, 1–3 min.
• Microetch: approximately 2%, 28–42°C, about 2 min; typical copper removal 1–2 µm.
• Predip: 15–30°C, less than 1 min.
• Tin bath: 63–73°C horizontal or 56–65°C vertical; typical dwell 7–11 or 9–15 min.
• Warm rinse 50–60°C, followed by a 50°C DI rinse.

These are reference values from supplied chemistry literature. Production parameters must follow the approved chemical supplier specification and KKPCB process control plan.

Immersion Silver — Performance

• Planar finish with consistent solderability and low contact resistance.
• Supports multiple reflow cycles and can be suitable for aluminium-wire bonding when correctly specified.
• Offers good solder-joint strength, touch-contact functionality and a comparatively simple process route.
• Long shelf life and tarnish resistance depend on correct production, handling and packaging.

Immersion Silver — Handling & Storage

• Always use clean, dry gloves. Fingerprints, salts, acids and oils can cause tarnish and reduce solderability.
• Routing before silver deposition is preferred. If routing follows plating, use sulfur- and acid-free interleaving material.
• Clean only with DI water or electrostatic methods; avoid surfactant or acid cleaners. Use dedicated drying equipment.
• Package promptly after cooling. Avoid chloride- and sulfide-bearing materials.
• Store at no more than 30°C and 75% RH in sealed bags or containers; wrap first in sulfur-free paper so plastic does not touch the silver directly.
• Keep desiccant away from direct board contact, positioned between plastic layers.
• Do not use adhesive tape, labels, ink or rubber bands in direct packaging contact.
• Properly produced and stored boards can retain properties for at least 12 months. After opening, rewrap and assemble promptly; an often-used mid-assembly guideline is about one week, subject to the actual environment.
• If stress-relief baking is required, protect the boards with aluminium foil.

OSP Handling

• Uniform copper cleaning and microetching are essential before organic passivation.
• Avoid fingerprints, abrasion, excessive heat exposure and contamination after coating.
• OSP is economical and very flat, but the supplied comparison limits multiple solderability to 1–2 cycles.
• Use controlled storage and an assembly profile compatible with the selected OSP chemistry.

Inspection & Release

• Confirm visual uniformity, coverage and absence of discoloration, stains or exposed base metal.
• Verify thickness against the approved finish specification and drawing notes.
• Where required, evaluate solderability, contact function, wire bonding, press-fit or corrosion performance using application-specific tests.
• Packaging and labeling must preserve the finish through shipment and customer storage.