IPC-4556 印制板化学镍钯浸金（ENEPIG）规范ENG - 第21页

the IPC-6010 sectional speciﬁcation. 4.2.1 Thickness Measurements Thickness measurement frequency shall be in accordance with T able 3-1. The number of readings per panel should be enough to calculate a signiﬁcant standa…

4.1.2 Sample Test Coupons Test specimens used for qualiﬁcation of printed boards with ENEPIG ﬁnish may be found in

IPC-2221 and/or noted in IPC-6010 sectional speciﬁcations. Alternatively, the supplier may create test patterns or process

control coupons to accommodate qualiﬁcation testing and/or lot conformance deposit thickness measurements. Specimen(s)

should be obtained or developed for qualiﬁcation testing to the requirements listed in Table 4-1.

Table 4-1 Suggested Fabricator Qualiﬁcation Plan

Requirement Test Reference Remarks

XRF Certiﬁcation Suitably calibrated XRF instrument with detector

capable of measuring tri-level thin coatings.

Use of certiﬁed national ENEPIG standards as

referenced in Appendices 3, 4, 9 and 10.

Note: Do not use electrodeposited standards or ones

with thicknesses outside the target thickness range

under evaluation.

Perform XRF certiﬁcation by performing a gauge

R&R or equivalent statistical approach. Use of the

correct certiﬁed national standards is critical. This

data may be used as to begin building a suitable

deposit thickness distribution database.

Deposit Thickness

Distribution

Suitable test pattern or production board/panel

having the correct surface area pads as described in

Appendices 3, 4, 9 and 10.

The deposit thickness database to demonstrate 4

sigma distribution should include sample readings

from product processed through the production

baths. Include readings from both front and. back

of the panels. Also, map thickness as a function of

panel position within a basket. It is suggested that

thickness measurements be made at panel locations

that provide as complete panel coverage as possible,

e.g., diagonal, four corners and center, each PWB

within a panel.

Visual Ref. paragraph 3.1 Perform visual inspection per applicable requirements

at a production ﬁnal inspection workstation and

document the appearance of the ﬁnish. It is

recommended to create an inspection checklist.

Solderability

(Wetting Balance)

Use suitable coupon(s) to perform J-STD-003

Category 3 testing.

See paragraphs 3.5 and 3.5.1.

Note: IPC-1601 provides guidance on packaging and

handling of coupons.

It is recommended to qualify to Category 3,

the highest level of storage coating durability

in J-STD-003.

Wire Bondability Test specimen suitable for use with MIL-STD 883,

METHOD 2011.8, or user deﬁned test pattern/

speciﬁcation.

Method 2011.8 of MIL-STD-883 is the most

commonly used test method requirement for

determining wire bond strength. Other user-deﬁned

AABUS measurements may be required. Document a

sufficient quantity of bond pulls to establish capability.

Assistance by the user may be required to support

this method.

Ionic Cleanliness Suitable specimen for IPC-5704

Ion Chromatography (IC) Testing.

IC testing per IPC-5704 is recommended during

qualiﬁcation to conﬁrm that the process and

associated rinses are adequate to ensure that no

contaminates remain that might not meet next level

assembly requirements. Periodic re-qualiﬁcation may

be necessary to account for changes in materials

and processes.

PTH Coverage Suitable Through Hole specimens for

microsectioning.

Microsection a number of ‘‘as received’’ specimen(s)

using darkﬁeld illumination (before solder ﬂoat).

Utilize coupon specimens from a variety of locations,

for example, from the outside and center panels of a

basket load.

Effect on

Soldermask

Adhesion

Para 3.4 - Suitable coupon of IPC-2221 or production

part containing high density features.

Utilizing an appropriate specimen, benchmark

adhesion of solder mask. Inspect to Quality

conformance requirements, or as speciﬁed

by User. Note whether the solder mask was

applied before or after ENEPIG processing.

Repeatability at

Various Stages of

Loading and Bath

Life

Applicable specimens of the Qual Plan. Repeat aspects of the Qualiﬁcation Testing at various

bath life metal turn-over (MTO) stages, as applicable,

looking for any impacts on deposition thickness or

distribution, (for example, for new baths and late

MTO).

IPC-4556 January 2013

the IPC-6010 sectional speciﬁcation.

4.2.1 Thickness Measurements Thickness measurement frequency shall be in accordance with Table 3-1. The number of

readings per panel should be enough to calculate a signiﬁcant standard deviation. A minimum of 20 readings per lot is sug-

gested.

Table 4-2 C=0 Sampling Plan (Sample Size for Speciﬁc Index Value

4.2.2 Qualified Processes If a qualiﬁed process has been established, the requirements of 4.1.1 for a minimum number of

readings and calculation of an associated standard deviation can be waived. For a qualiﬁed process, demonstrating a process

capability (± 4 sigma) within the appropriate speciﬁcation, a sample measurement consistent with Table 3-1 may be used for

lot conformance, provided all readings fall within the Qualiﬁed Process population (± 4 sigma). Alternative thickness inspec-

tion methodologies shall be AABUS.

For gauge capability and GaugeR&R,seeAPPENDIX 10.

)

Lot Size

Class 1 Class 2 Class 3

2.5

4.0

6.5

1.5

2.5

4.0

0.10

1.0

2.5

4.0

1-8 5 3 3 ** 5 3 ** ** 5 3

9-15 533853**1353

16-25 533853**1353

26-50 775877**1377

51-90 11 8 5 13 11 8 ** 13 11 8

91-150 11 9 6 19 11 9 125 19 11 9

151-280 13 10 7 19 13 10 125 29 13 10

281-500 16 11 9 21 16 11 125 29 16 11

501-1200 19 15 11 27 19 15 125 34 19 15

1201-3200 23 18 13 35 23 18 125 42 23 18

3201-10,000 29 22 15 38 29 22 192 50 29 22

10,001-35,000 35 29 15 46 35 29 294 60 35 29

Note 1. Index Value is associated to the A.Q.L. value. If a particular product is determined to be ‘‘critical’’ by the user and a smaller index value is required,the

user shall designate the requirement in the procurement document and should state the ‘‘critical’’ requirement on the master drawing. **Denotes

inspect entire lot.

4.2 Quality Conformance Testing Quality conformance testing shall consist of inspections as speciﬁed in Table 3-1 and

January 2013 IPC-4556

APPENDIX 1

Chemical Definitions and Process Sequence

Martin Bayes

Dow Electronic Materials

Chemical Definitions

Electroless Process – This chemical process promotes sustained deposition of a metal or metal alloy onto either a dielec-

tric or metallic PWB surface through an oxidation-reduction chemical reaction, without the application of an external elec-

trical potential. Reducing agents, such as sodium hypophosphite or sodium formate, react at catalytic surfaces to release elec-

trons, which immediately reduce the positively charged metal ions (e.g., nickel ions in ENIG and ENEPIG and palladium

ions in ENEPIG), promoting their deposition onto the PWB.

This type of reaction is described as ‘‘autocatalytic,’’ as the deposition process will continue even after the substrate is com-

pletely covered by a continuous layer of the plated deposit. The deposit thickness will therefore continue to rise in the pres-

ence of source metal ions and a reducing agent, until the board is removed from the plating bath. The thickness of plated

deposits will vary depending on the bath temperature, chemical parameters (such as solution pH) and the amount of time

spent in the plating bath.

Immersion Process – This chemical process uses a chemical displacement reaction to deposit a layer of a second metal onto

a base metal surface. In this reaction, the base metal dissolves, releasing the electrons that reduce the positively charged ions

of the second metal present in solution. Driven by the electrochemical potential difference, the metal ions in solution (e.g.,

gold ions in ENIG or ENEPIG process) are deposited onto the surface of the board, simultaneously displacing ions of the

surface metal into solution.

This type of reaction is described as ‘‘self-limiting’’ because, once the base metal is covered with a continuous layer of the

deposited metal, there is no longer a source of electrons and the reaction ceases.

Process Sequence

1. Cleaner – The purpose of this step is to clean the copper surface in preparation for processing. The cleaner removes

oxides and light surface contaminants, and ensures that the surface will be in a condition allowing it to be uniformly

micro-etched. Vendor speciﬁcations for temperature, dwell time, agitation and bath chemical control should be followed.

2. Microetch – The purpose of this step is to produce a surface that may be uniformly catalyzed and plated with good deposit

adhesion by removing some copper from the surface. A variety of different etchant types may be used (e.g., sodium per-

sulfate, peroxide/sulfuric). Vendor speciﬁcations for temperature, dwell time, agitation and bath chemical control should

be followed.

3. Catalyst – The purpose of this step is to deposit a material that is catalytic to electroless nickel plating on the copper

surface. The catalyst lowers the activation energy for nickel deposition and allows plating to initiate on the copper sur-

face. Examples of metal catalysts include palladium and ruthenium (typically deposited by an immersion reaction with

the copper surface). Vendor speciﬁcations for temperature, dwell time, agitation and bath chemical control should be fol-

lowed.

4. Electroless Nickel – The purpose of this bath is to deposit the required thickness of nickel on the catalyzed copper sur-

face. The nickel thickness should be adequate to cover the copper with a substantially pore-free coating, to create a dif-

fusion barrier to copper migration, and also serve as a solderable surface, depending on the intended application.

The nickel bath has a relatively high deposition rate and its active chemical components must be maintained in balance

on a continuous basis, by addition of appropriate replenishment components. Electroless nickel baths typically run at high

temperatures and extended dwell times to achieve the required deposit thickness. It is therefore important to ensure that

compatible PWB substrate and solder mask materials are used. Vendor speciﬁcations for temperature, dwell time, agita-

tion and bath chemical control should be followed.

5. Electroless Palladium – The purpose of this bath is to deposit the required thickness of palladium onto the initial elec-

troless nickel deposit. The palladium thickness should be adequate to provide a surface with the desired solderability

and/or wire bonding characteristics, depending on the intended application. This bath runs at moderately high tempera-

tures. Dwell times will vary, depending on the required deposit thickness. Vendor speciﬁcations for temperature, dwell

time, agitation and bath chemical control should be followed.

6. Immersion Gold – The purpose of this step is to deposit a thin, continuous layer of gold. The gold protects the underly-

ing electroless nickel/electroless palladium layers from oxidation or passivation, and also serves as a contact surface,

IPC-4556 January 2013