IPC-4552.pdf
IPC-4552 July 2002 Specification for Electroless Nickel/Immers ion Gold (ENIG) Plating for Printed Circuit Boards Plating Subcommittee (4-14) Interim Final Proposed by IPC 2215 Sanders Road, Northbrook, IL 60062 Phone : …
IPC-4552
July 2002
Specification for
Electroless Nickel/Immersion Gold (ENIG) Plating
for Printed Circuit Boards
Plating Subcommittee (4-14)
Interim Final
Proposed by IPC
2215 Sanders Road,
Northbrook, IL 60062
Phone : (847) 509-9700
Fax : (847) 509-9798
URL : www.ipc.org
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IPC-4552
Specification for Electroless Nickel/Immersion Gold (ENIG) Plating
for Printed Circuit Boards
Table of Content
1
SCOPE.................................................................................................................................................................................... 1
21
1.1
S
COPE
.............................................................................................................................................................................. 1
1.2
D
ESCRIPTION
.................................................................................................................................................................... 1
1.2.1
Phosphorus/Boron Content .................................................................................................................................... 1
1.3
O
BJECTIVE
....................................................................................................................................................................... 1
1.4
P
ERFORMANCE
F
UNCTIONS
............................................................................................................................................... 1
1.4.1
Solderability ........................................................................................................................................................... 1
1.4.2
Contact Surface ...................................................................................................................................................... 1
1.4.3
EMI Shielding......................................................................................................................................................... 1
1.4.4
Conductive (Replacement for Solder) and/or Anisotropic Adhesive Interface .....................................................
1.4.5
Connectors ............................................................................................................................................................. 2
1.4.6
Aluminum Wire Bonding ........................................................................................................................................ 2
2
APPLICABLE DOCUMENTS ............................................................................................................................................. 2
3
REQUIREMENTS................................................................................................................................................................. 3
3.1
V
ISUAL
............................................................................................................................................................................ 3
3.2
F
INISH
T
HICKNESS
............................................................................................................................................................ 5
3.2.1
Electroless Nickel Thickness .................................................................................................................................. 5
3.2.2
Immersion Gold Thickness ..................................................................................................................................... 5
3.3
P
OROSITY
......................................................................................................................................................................... 5
3.4
A
DHESION
........................................................................................................................................................................ 5
3.5
S
OLDERABILITY
................................................................................................................................................................ 5
3.6
C
LEANLINESS
................................................................................................................................................................... 5
3.7
C
HEMICAL
R
ESISTANCE
.................................................................................................................................................... 5
3.8
H
IGH
F
REQUENCY
S
IGNAL
L
OSS
....................................................................................................................................... 5
4
QUALITY ASSURANCE PROVISIONS ............................................................................................................................ 6
4.1
Q
UALIFICATION
................................................................................................................................................................ 6
4.1.1
Sample Test Coupons ............................................................................................................................................. 6
4.2
A
CCEPTANCE
T
ESTS
......................................................................................................................................................... 6
4.3
Q
UALITY
C
ONFORMANCE
T
ESTING
................................................................................................................................... 6
APPENDIX 1
CHEMICAL DEFINITIONS...................................................................................................................... 7
APPENDIX 2
PROCESS SEQUENCE.............................................................................................................................. 7
APPENDIX 3
QUALIFICATION OF ENIG PROCESS BY THE BOARD SUPPLIER.............................................. 8
APPENDIX 4
RECOMMENDATION FOR THICKNESS MEASUREMENT............................................................. 8
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IPC-4552 Proposal June 2001
IPC-4552
Specification for Electroless Nickel/Immersion Gold (ENIG) Plating
for Printed Circuit Boards
1 SCOPE
1.1 Scope
1.2
1.2.1
1.3
1.4
1.4.1
1.4.2
1.4.2.1
1.4.2.2
1.4.3
This specification sets the requirements for the use of Electroless nickel/immersion Gold (ENIG) as a surface finish
for printed circuit boards. This specification is intended to set requirements for ENIG deposit thicknesses based on
performance criteria. It is intended for use by supplier, printed circuit manufacturer, electronics manufacturing
services (EMS) and original equipment manufacturer (OEM).
Description
ENIG is an electroless nickel layer capped with a thin layer of immersion gold. It is a multifunctional surface finish,
applicable to soldering, aluminum wire bonding, press fit connections, and as a contact surface. The immersion gold
protects the underlying nickel from oxidation/passivation over its intended life. However, this layer is not totally
impervious and it will not pass the requirements of a ‘classic’ porosity test.
Phosphorus/Boron Content
Phosphorus or boron containing reducing agents are used for the reduction of the electroless nickel during the
deposition process. Phosphorus or boron is thus incorporated in the nickel deposit. The level of these co-deposited
elements should be controlled within the specified process limit. Variation of phosphorus or boron level, outside the
specified process limits, may have adverse effects on the solderability of the finish.
Objective
This specification sets the requirements specific to ENIG as a surface finish. As other finishes require specifications,
they will be addressed by the IPC Plating Processes Subcommittee as part of the IPC-4550 specification family. As
this and other applicable specifications are under continuous review, the subcommittee will add appropriate
amendments and make necessary revisions to these documents.
Performance Functions
Solderability
This primary function of ENIG is to provide a solderable surface finish that has extensive shelf life and that is
suitable for all surface mount and through-hole assembly applications. Due to the minimal thickness of the
immersion gold layer, the possibility of gold embrittlement of the solder joint is negligible.
Contact Surface
There is a substantial amount of experience using ENIG for the following applications:
Membrane Switches
ENIG is the de facto standard for membrane switches.
The ENIG surface finish with as little as 0.025µm (0.984µin) of immersion gold is suitable for 1.5 million actuations
with negligible resistance change.
Metallic Dome Contacts
The Subcommittee attempted to complete this section, but was unable to obtain the necessary data to do so, at this
time. Whenever possible, such data should be submitted to the IPC 4-14 Plating Processes Subcommittee to be
considered for inclusion in upcoming revisions of this standard.
EMI Shielding
ENIG is one of the surface finishes used as an interface between electromagnetic interference (EMI) shielding and
the printed wiring board (PWB).
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