When a PCB is produced, a number of factors are taken into account, including the PCB layout itself, the material requirements, the laminates, inner layers, and the layer stack of the board. However, engineers frequently pay less attention to the surface finish. Most understand that the soldering of the components would be compromised if the PCB's bare copper was allowed to oxidise but don’t understand which PCB finish they should specify. Generally speaking, the primary factors to consider are the amount of storage needed, the final use, the assembly procedure, the PCB design itself, and of course, the cost. Here is a quick description of each. Contact us for advice on any additional concerns you may have about an appropriate finish for your application.
OSP (Organic Solderability Preservative)
Standard thickness : 0.20 - 0.65µm
Shelf Life : 6 months
OSP is a popular ecologically friendly finish which is reasonably priced and that helps to prevent copper oxidation and enhances solderability. Suitable for multiple heat cycles during the assembly process.
HASL – Lead Free Hot Air Solder Level. (Sometimes called LF HASL)
Standard thickness : 1 - 40µm
Shelf Life : 12 months
HASL involves submerging the PCB in molten solder to completely coat the copper with solder. The PCB is then passed between hot air knives to remove any excess solder.
Good value and excellent solderability is provided by the HASL method. It allows for several thermal cycles, but due to the possibility of solder bridging, it is not necessarily appropriate for fine pitch SMD and BGA. Ceramic circuits and Extreme Heavy Copper are not a good fit for HASL.
Leaded HASL is also available but this is not offered on-site at GSPK
ENIG - Electroless Nickel Immersion Gold
Standard thickness :Nickel 3 - 6µm, Gold 0.05 - 0.10µm
Shelf Life : 12 months
The Hot Air Solder Level (HASL) process may not provide the flatness needed for PCB designs that use finer lines and micro vias. ENIG is a well-liked alternative finish for BGA, fine pitch, and small components. ENIG can also be wire-bonded.
ENEPIG - Electroless Nickel Electroless Palladium Immersion Gold
Standard thickness :Nickel 3 – 6µm, Palladium is 0.05 – 0.25µm, Gold 0.05 – 0.07µm
Shelf Life : 12 months
ENIG may raise questions about BGA for "Black Pad." Nickel corrosion on electroless nickel and gold immersion is referred to as "Black Pad". This term refers to a condition where joints break as a result of pressure, exposing corroded nickel.
ENEPIG, an improved version of ENIG, has the ability to solve the Black Pad problem.
With the correct thickness the palladium creates a dense layer to prevent the Nickel from oxidising. The palladium layer reduces the aggressive replacement reaction between the gold and nickel. Higher thickness of palladium limit the amount of Gold that can be deposited.
Excellent wire bonding and reflow soldering capabilities are also strengths of the ENEPIG process.
EPAG - Electroless Palladium Autocatalytic Gold
Shelf Life : 12 months
EPAG (Electroless Palladium Autocatalytic Gold) is a direct palladium surface finish method using "Autocatalytic Gold" as an optional gold coating. This enables a larger Gold thickness on the Electroless Palladium, making it more versatile in terms of assembly processes like gold wire bonding and soldering.
It is suitable for non-magnetic applications since it contains no nickel.
Features and benefits include:
- High-density circuitry is possible
- Low-temperature processes for high-frequency materials
- Provides a plane surface on which to solder
- Suitable for Cu, Al, Ag, Cu-Pd, and Au wire bonding
- Used with conductive adhesives
- Appropriate for ceramics
- Thermo-compression bonding
- Supports applications for flex
- An increase in high frequency performance
- Allowing for very fine L/S with a thickness of 0.2µm
Immersion Tin
Standard thickness :≥ 1.0µm
Shelf Life : 6 months
Immersion Tin is perfect for small components, fine pitch, BGA and press fit technology because it has excellent flatness. The method has a mid-range cost and good solderability.
Tin whiskers, which are aggressive toward solder masks and are the process' principal cause for concern and necessitate the use of a larger solder mask dam than usual. The process utilised by GSPK contains an additive to inhibit whisker growth. Additionally, because it is so delicate when handled, gloves must be used
Immersion Silver
Standard thickness :0.12 – 0.4µm
Shelf Life : 6 months
Silver has great conductivity and a smooth, solderable surface, both of which are advantageous to the integrity of signal transmission. Similar to tin, its flatness makes it perfect for BGA, fine pitch, and small components. However, it is extremely delicate when handled and can tarnish quickly, necessitating specific packing and prompt resealing of unused boards.
Hard Gold
Shelf Life : 12 months
Hard Gold is becoming less popular as a finish. When an extremely durable surface treatment is required, this electroplating procedure is frequently used. Historically, it was applied on edge connectors where a finish devoid of oxide must be wear resistant. Nowadays, many consumers pick ENIG over Hard Gold. Hard Gold is available but is not offered on-site at GSPK.
