Printed Circuit Boards (PCBs) - Lead-free and RoHS-compliant

Description:
This is a chemo-physical process in which soldered tin deposits evenly on the coper tracks.

• Plane surface
• Good for fine-pitch apllications
• Best surface for press fit connectors
• Great acceptance in Europe
• Rapidly growing demand in Asia
• Cost-efficient

• Storage time for subsequent processing of up to 6 months
• Not suitable for bonding
• Sensitive to handling(finger prints prevent solderability)
• Possiblity of multiple solder process are limted (reflow soldering with nitrate is advised).
• Pure tin´s layer thickness is greatly reduced with additional soldering:
  

  Working cycle	Pure tin layer after working cycle
  Tinning	1,19µm
  Reflow soldering
  1x	0,39µm
  2x	0,25µm
  3x	0,25µm
  5x	0,18µm
  Source: Atotech www.atotech.de

• Therefore 2 time reflow soldering requires a tin layer of =1µm (recommended =1,2µm)
• Not suitable for bonding

Discription: This is a solder process in which hot tin difusses into the copper surface. The circuit boards are dipped into hot tin and are then blasted with compressed air with (HAL = Hot Air Leveling).

Advantages:

• Easy solderability due to the large solder supply on the pads.
• Great acceptance in Europe
• Storage time for subsequent processing of up to 12 months
• Less sensitive to handling than immersion tin
• Cost-efficient

• Surface less level than immersion tin
• Not suitable for bonding
• Limited suitablity for fine-pitch apllications due to uneveness
• Possiblity of multiple solder process are limted (reflow soldering with nitrate is advised).
• Higher solder temperature necessary (about 260°C)
• Higher copper dissolvance due to the higher tinning temperature
• High thermal stress during production (PCB material with Tg 150 are recommended = LeitOn standard)

Discription: This is a chemico-physical processe where dissolved nickel is followed by dissolved gold to evenly settle on the pads. The layer thickness for is about 4µm for nickel and about 0,1µm for gold for circuit boards with aluminum wire bonding (ultrasonic bonding). Thick gold for gold wire bonding (thermal bonding) require a gold thickness of 0,8 to 1,0µm next to the nickel layer.

Advantages

• Best avaiable surface
• Ideale surface for fine-pitch application
• Storage time for subsequent processing of up to 12 months
• Bonding possible
• Very good solderability
• No copper accummulation of solder in the soldering bath, as the nickel layer will provide protection.

• Very cost intensive lamination process
• Requires a high degree of solder bath expertise and specialization.

Desicription: This is a chemo-physical process in which dissolved silver envenlly distributes on to the copper pads.

Advantages

• Good solderability
• Plane surface
• Storage time for subsequent processing of up to 6-12 months
• Very good for fine-pitch applications
• Mulitple solder processes are possible
• Cost efficient and fast process
• High acceptance in the USA

• Offerd only by few producers
• Limited acceptance and popularity in Europe
• Sensitive surface due to low layer thickness of 0,2µm Ag

Discription: This is a kind of clear solder laquer which protects the copper surface from corrosion.

Advantages:

• Plane surface
• Very good for fine-pitch applications
• Very fast process
• Very inexpensive process
• Very popular for price sensitve mass production in the consumer goods sector

• Bonding not possible
• Storagetime of about 3 - 6 months
• Bad reputation due to experience with older solder masks
• Offered by very few producers