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ViaLife PlusTM is a propriety process developed by TTM Technologies. ViaLife
Plus combines 2 proven surface finishes on a PWB in order to take advantage of their
intrinsic properties. Over the last 10 years, the PWB industry has confirmed through
industry stress testing methodology Ni/Au coatings strengthen via hole walls and
improves long-term reliability. This has become extremely important due to increased PWB aspect ratios and increased
thermal exposure at assembly. However, with the continued introduction of high density high I/O BGA patterns,
Electroless Nickel / Immersion Gold (ENIG) is not the ultimate finish where thermal expansion coefficients between the
large IC package and the PCB creates a combination of tangential and vertical stress at the solder joint. ENIG produces
a Ni-Sn intermetallic solder joint that is not as robust as Cu-Sn intermetallic material that is formed at assembly for
surface finishes such as Organic Solder Protection (OSP), Immersion Silver and Immersion Tin.
The ViaLife PlusTM is a simple solution that simultaneously increases hole reliability and creates the most robust solder
joint. First, via holes are selectively plated with ENIG leaving the surface mount pads for IC and other components to be
assembled with an alternative finish such as OSP, Silver or Tin. This combination or "multi" finishing provides the
advantages of increased via hole reliability as well as the most robust Cu-Sn intermetallic solder joints.
Current Industry Problems and Solutions:
Disadvantages of 100% ENIG:
- Brittle Ni-Sn solder joints - e.g., BGA solder joint interfacial fractures due to tensile stress associated with BGA package to PCB differences in thermal expansion coefficients
- Incompatible with some solder masks
- Industry variations due to different process chemistries
- Potential cost impact across industry
Advantages of ENIG:
- Three fold increase in barrel and via reliability
- Ni barrier makes for the most successful rework
- Very uniform flat surface-compatible with HDI
- Handling tolerance
- Good shelf life (~12 months)
- Conductive surface for reliable electrical testing
- Withstands multiple assembly operations
Advantages of ViaLife Plus™
ENIG plus alternative surface finishes:
- The advantages of ENIG in the holes without the disadvantages of Ni-Sn solder joints.
- Via holes coated with ENIG have improved reliability by factor of 3 compared to Cu alone.
- ENIG can also be plated to selective non-solderable surface features.
- Selective ENIG can be combined with Immersion Ag, OSP or Immersion Sn, which produce a more robust Cu-Sn intermetallic solder joint.
- Combines the best attributes of ENIG (via hole reliability) and OSP, Immersion Ag or Immersion Sn (Cu-Sn solder joints)
- Best for High I/O BGAs and high aspect ratio via holes
- ViaLife PlusTM is a drop in at assembly.
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