PCB Tech - Experts summarize PCB surface treatment technology

Experts summarize the characteristics, advantages and disadvantages of various surface processes produced by PCB surface treatment technology

The solderability of bare copper itself is very good, but it is easy to be oxidized. In order to ensure the good solderability and electrical properties of PCB products, technical experts have summarized the characteristics, advantages and disadvantages of various surface processes!

OSP

Main feature: Cover a layer of organic protective film on the copper surface

Thickness control: 0.2~0.6um

Advantages: uniform film thickness and low cost

Disadvantages: difficult to withstand multiple reflow soldering

Shen Yin

Main feature: A silver layer is covered on the copper surface through displacement reaction

Thickness control: 0.2~0.4um

Advantages: uniform silver layer, average cost, long storage period

Disadvantages: easy to oxidize, and it is difficult to completely solve the discoloration and yellowing of the silver surface, which affects the solderability

Shen Xi

Main feature: Cover a layer of tin on the copper surface through displacement reaction

Thickness control: ≥1.0um

Advantages: uniform tin layer, average cost, easy to aging

Disadvantages: the potion is easy to age, and the problem of tin whiskers is difficult to solve

Spray tin

Main features: through physical means, hot air leveling to obtain a protective layer

Thickness control: 2~40um

Advantages: solderability, best compatibility, long storage period

Disadvantages: lead, poor flatness

Lead-free spray tin

Main features: through physical means, hot air leveling to obtain a protective layer

Thickness control: 2~40um

Advantages: simple process, substitute for tin spraying, long storage period

Disadvantages: poor flatness, fluidity, poor solderability

Immersion Nickel Gold

Main feature: Cover a thin layer of nickel and gold on the copper surface through displacement reaction

Thickness control: 0.05~0.1um

Advantages: uniform coating, good solderability, long storage period

Disadvantages: high cost, plagued by black disk problems

Nickel Palladium

Main feature: Deposit a thin palladium layer before immersing gold

Thickness control: 0.05~0.1um

Advantages: suitable for wire bonding, reducing gold costs

Disadvantages: not widely adopted

Electric hard gold

Main feature: Cover a thin nickel-gold layer on the copper surface through electrochemical oxidation-reduction reaction

Thickness control: 0.38~2.0um

Advantages: wear resistance, oxidation resistance, low resistance

Disadvantages: poor solderability, high cost, used according to performance needs

Golden finger

Main feature: Cover a thin nickel-gold layer on the copper surface through electrochemical oxidation-reduction reaction

Thickness control: 0.25~1.5um

Advantages: wear resistance, oxidation resistance, low resistance

Disadvantages: poor solderability, high cost, used according to performance needs

Full board gold-plated

Main feature: Cover a thin nickel-gold layer on the copper surface through electrochemical oxidation-reduction reaction

Thickness control: 0.025~0.1um

Advantages: uniform coating, suitable for wire bonding

Disadvantages: high cost

The above is a summary of the surface treatment technology of PCB circuit boards