IPC-4552.pdf - 第4页

IPC-4552 Proposal June 2001 2525 1.4.4 1.4.5 1.4.5.1 Press 1.4.5.2 1.4.6 Conductive (Replacement for S older) and/or Anis otropic Adhesive Interface ENIG is ideally suited as an interface for a nisotropic adhesi ve appli…

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).

Page 1 of 2525

Download From http://bbs.infoeach.com

IPC-4552 Proposal June 2001

2525

1.4.4

1.4.5

1.4.5.1 Press

1.4.5.2

1.4.6

Conductive (Replacement for Solder) and/or Anisotropic Adhesive Interface

ENIG is ideally suited as an interface for anisotropic adhesive applications (the use of a conductive adhesive as an

alternative to solder).

Connectors

Fit

Press fit requirements shall meet Telcordia GR-1217-CORE. Excessive nickel thickness can lead to concerns with

press fit insertion forces.

Edge Tab

The ENIG surface finish is suitable for plug-to-install applications (five insertions/withdrawals) using low insertion

force (LIF) or zero insertion force (ZIF) connectors. ENIG is not suitable as an edge connector for multiple insertion

(more than five) withdrawals or high insertion force applications. This application generally requires an alternate

metallic finish, such as electrolytic hard gold.

Aluminum Wire Bonding

ENIG meets the requirements of MIL-STD-883, Method 2011.7. Variables that affect performance include

cleanliness, substrate materials, wire thickness and surface topography. ENIG is not a surface leveler; the surface

topography largely depends on the conditions of the underlying copper surface.

2 APPLICABLE DOCUMENTS

J-STD-003 Solderability Tests for Printed Boards

IPC-2221 Generic Standard on Printed Board Design

IPC-6011 Generic Performance Specification for Printed Boards

IPC-6012 Qualification and Performance Specification for Rigid Printed Boards

IPC-6013 Qualification and Performance Specification for Flexible Printed Boards

IPC-TM-650 Test Method Manual

2.3.25 Detection and Measurement of Ionizable Surface Contaminants by Resistivity of Solvent Extract

(ROSE)

2.4.1 Adhesion, Tape Testing

ASTM B607-91 (1998), Standard Specification for Autocatalytic Nickel Boron Coatings for Engineering Use

ASTM B733-97, Standard Specification for Autocatalytic (Electroless) Nickel-Phosphorus Coatings on Metal

MIL-STD-883, Method 2011.7 Test Method Standard, Microcircuits – Bond Strength (Destructive Bond Pull Test)

Telcordia GR-1217-CORE Generic Requirements For Separable Electrical Connectors Used In Telecommunications

Hardware

ISO-4527 “Auto-Catalytic Nickel-Phosphorous Coatings; Specifications and Test Methods”

Annex A: Determination of Coating Thickness and

Annex D: Determination of Coating Composition (Nickel and Phosphorous Content).

Page 2 of

Download From http://bbs.infoeach.com

IPC-4552 Proposal June 2001

3 REQUIREMENTS

Table 3-1 Requirements of Electroless Nickel Immersion Gold Plating

Tests Test

Method

Requirement

Paragraph

Class 1 Class 2 Class 3

General

Visual Visual 3.1 Uniform plating and complete coverage of surface to

be plated

Electroless Nickel

Thickness

APPENDIX 4

3.2.1

3 to 6 µm

[118.1 to 236.2 µin]

Immersion Gold

Thickness

APPENDIX 4 0

0.05 µm minimum

[1.97 µin minimum]

Porosity N/A 3.3 N/A

Physical

Adhesion/Tape Test

IPC-TM-650

TM 2.4.1

3.4 No evidence of plating removed

Solderability

J-STD-003 3.5 Meet solderability requirements of Category 3

durability with 6 months shelf life.

Chemical

Phosphorous/Boron

Content

ASTM B733-

97 & ASTM

B607-91

(1998)

1.2.1 (Reference Only; Supplier Dependent – No Testing

Required)

Chemical Resistance N/A 3.7 N/A

Electrical

High Frequency

Signal Loss

(1)

3.8 TBD TBD TBD

Contact Resistance

(1)

1.4.2 TBD

Environmental

Cleanliness

IPC-TM-650

TM 2.3.25

3.6

Max. 1.56 µg/cm

(1)

An appropriate IPC-TM-650 test method used to generate data for this electrical property is not available at the

time of this writing.

3.1

Visual

ENIG surfaces shall be inspected in accordance with the visual examination sections of the IPC-6011 series, and

specifically IPC-6012 which specifies a nominal magnification of 1.75X (approx. 3 diopters). The coverage shall be

complete and the finish shall be uniform on the surface to be plated (Figure 3-1). There shall be no extraneous

plating or nickel foot (Figure 3-2), edge pull back (Figure 3-3) or skip plating (Figure 3-4) on the plated surface for

all classes of product.

Page 3 of 2525

Figure 3-1 Uniform Plating

Download From http://bbs.infoeach.com