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IPC issues ENEPIG specs.

The IPC Plating Processes Subcommittee 4-14, co-chaired by George Milad and Gerard O'Brian, has finalized specifications for an ENEPIG Surface Finish, IPC-4556.

The electroless nickel thickness shall be 3 to 6 [micro]m [118.1 to 236.2 pin] at [+ or -] 4 sigma (standard deviations) from the mean as measured on a nominal pad size of 1.5 mm x 1.5 mm [0.060 in x 0.060 in] or equivalent area, where standard feature size tolerances as expressed in the IPC-6010 standard series, apply. The upper end of this thickness specification has been chosen based on concerns with insertion force issues for compliant pin applications only. Use of thicknesses outside of this range shall be AABUS.

The electroless palladium thickness shall be 0.05 to 0.15 pm [2 to 12 pin] at [+ or -] 4 sigma (standard deviations) from the mean as measured on a nominal pad size of 1.5 mm x 1.5 mm [0.060 in x 0.060 in] or equivalent area, where standard feature size tolerances as expressed in the IPC-6010 standard series, apply. The upper thickness limit may be exceeded to meet special design criteria (for example, wire bonding). However, the committee has data showing that excessive electroless palladium thicknesses may impair solder joint reliability.

The minimum immersion gold thickness shall be 0.025[micro]m [1.2 pin] at - 4 sigma (standard deviations) below the mean as measured on a nominal pad size of 1.5 mm x 1.5 mm [0.060 in x 0.060 in] or equivalent area, where standard feature size tolerances as expressed in the IPC-6010 standard series, apply. The specification is one sided, based on performance test results showing impaired solderability performance after accelerated aging at lower gold thicknesses. The nature of the reaction of immersion gold with electroless palladium is such that substantially greater thicknesses may not be achievable.

This important two-year effort saw major contributions from these OEMs: Raytheon, Lockheed Martin, Adtran, Boeing, BAE, Honeywell, Continental Automotive, Schneider Electric, Delphi, St. Jude Medical, RIM, Intel, HP and Oracle.

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Backplane Industry Proves Immersion Tin is Cleaner, Flatter, and 3x
Faster - and Ideally Suited for Press Fit Connectors

Attribute Specification Result Performance
 Rank

Ionic IPCTM 650 1 54 0.8 NaCI 40% less than
Cleanliness NaCI micrograms/in2 the
 micrograms/in2 specification

Thickness IPC 554 46 and 52 Potential to
uniformity Category 3 microinches satisfy
 minimum 40 with a 1.5 St category 3
 microinches dev requirements
 minus 4 sigma

Surface Crystalline Fine grain Preferred fine
analysis murphology crystalline grain deposit
 deposit resulting in
 excellent
 wettability

Solderaoility EIA IPC Wetting time Wetting time
 J-STD-003C 0.68 sec as improved with
 plated 1.1 sec bath age
 alter heat
 treat. Final
 force over 0 2
 mN/mm

Soldermask No lift at tape Average moan Allows
undercut test 2.5 micron less potential for
 than 0.1 mil reworkability


The Round Robin Test Summary is available through IPC. The subcommittee's next task is to update the (2002) specifications for ENIG.
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Publication:Printed Circuit Design & Fab
Date:Mar 1, 2013
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