IPC J-STD-003B.pdf - 第32页

5 EVALUATION AIDS 5.1 Evaluation Aids – Surface As an aid to evaluation of the test results (see Figure 5-1). This aid is to be used pri- marily to illustrate types of defects rather than percentage of area covered. 5.2 …

4.3.2 Test F1 – Wetting Balance Test: Lead-Free Sol-

der

This test is for wetting balance testing of plated-

through holes, surface conductors and attachment lands.

4.3.2.1 Apparatus A solder meniscus force measuring

device (wetting balance) which includes a temperature

controlled solder pot containing solder per 3.2.1 and main-

tained per 3.5.1 and 3.5.2 shall be used. The equipment

shall have a means of recording force as a function of time,

such as a chart recorder, data logger, or computer.

4.3.2.1.1 Dipping Device A mechanical or electrome-

chanical dipping device incorporated in the wetting balance

shall be used. The device shall be preset to produce an

immersion and emersion rate as speciﬁed in 4.3.1.3. The

test specimen dwell time is controlled to the time speciﬁed

in 4.3.1.3 (see Figure 4-7).

4.3.2.2 Test Specimen The test specimen shall be in

accordance with 1.7. The test specimen shall either be a

full board, a section of a board, or a suggested test speci-

men as illustrated in Figure 4-8. Test specimen preparation

shall be in accordance with 3.4.

4.3.2.3 Procedure After application of the ﬂux and par-

tial drying per 4.1, the test specimen shall be mounted on

the test equipment. After blotting away excess ﬂux from

the test specimen with a piece of absorbent clean material,

hang it on the apparatus so that its lower edge is 10 ± 1

mm [0.394 ± 0.039 in] above the solder bath to preheat it

for 20 ± 1 seconds. The test shall be started after clearing

of the surface dross from the molten solder and a waiting

period of5±5seconds for the bath to settle down.

The ﬂux covered surface shall be immersed only once in

the molten solder to a depth of 0.20 ± 0.1 mm [0.00787 ±

0.0039 in]. The angle of immersion shall be 20 ° - 40 °. An

angle of 90 ° may be used only upon agreement between

user and vendor on immersion angle selection. The

immersion/emersion rate shall be1mm-5mm[0.039 in

- 0.20 in] per second and the dwell time shall be 5.0 +

0/-0.5 seconds. Prior to examination, all test specimens

shall have the ﬂux removed using a cleaning agent in

accordance with 3.2.3 (see Figure 4-9).

4.3.2.4 Evaluation This test is intended for evaluation

purposes only (see 1.3).

4.3.2.4.1 Magnification Test specimens shall be exam-

ined at 10X using the equipment speciﬁed in 3.3.3.

4.3.2.4.2 Suggested Criteria The suggested criteria sets

for solderability evaluation are listed in Table 4-6. Figures

4-10 and 4-11 illustrate the suggested criteria of Table 4-6.

In addition, the area of the test sample with fresh solder

adhesion shall be greater than the area that was immersed

in the solder bath, (i.e., the printed board shall exhibit

positive solder wetting beyond its immersion depth).

4.3.2.5 Gauge Repeatability and Reproducibility (GR&R)

Protocol

Appendix D contains a suggested GR&R proto-

col that may be used by the vendor and user to insure that

the respective wetting balance equipment are correctly

calibrated.

Table 4-6 Wetting Balance Parameter and Suggested Criteria

Parameter Description

Suggested Criteriaa

Set A Set B

Time to buoyancy corrected zero ≤1 second ≤2 second

Wetting force at two seconds from

start of test

≥50% of maximum theoretical

wetting force at or before two

secondsb

Positive value at or before two

seconds

Wetting force at ﬁve seconds from

start of test

At or above the value of F2 At or above the value of F2

Integrated value of area of the

wetting curve from start of test

≥ area calculated using sample

buoyancy and 50% maximum

theoretical forcec

> zero (0)

a. These suggested criteria have been established in a two-tier evaluation format with Set A being more stringent. Components meeting Set A suggested

criteria are applicable to a larger soldering process window than components meeting Set B suggested criteria. It should be recognized that components

meeting Set B suggested criteria may be completely acceptable to a larger process window but the user must determine which criteria set best integrates

into their process.

b. See Appendix A for the method of calculating the maximum theoretical force.

c. See Appendix B for the method of calculation. (It is suggested that this method of calculation be programmed into the software used for control of the wetting

balance test equipment.)

March 2007 IPC J-STD-003B

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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5 EVALUATION AIDS

5.1 Evaluation Aids – Surface

As an aid to evaluation of

the test results (see Figure 5-1). This aid is to be used pri-

marily to illustrate types of defects rather than percentage

of area covered.

5.2 Evaluation Aids – For Class 3 Plated-Through

Holes

Proﬁle views of acceptable conditions are pre-

sented in Figure 4-5 for aid in visualizing all the common

conditions. The following are also acceptable conditions

for speciﬁc cases:

• Solderability acceptance for plated-through holes with

aspect ratios greater than 5:1 (board thickness: hole diam-

eter) shall be agreed upon by user and vendor.

• Depressed ﬁllets in holes are acceptable under the follow-

ing condition: the solder in partially ﬁlled holes must

exhibit a contact angle less than 90 ° relative to the hole

wall (see Figure 4-5 and 4-6).

• All holes less than 1.5 mm [0.0591 in] diameter shall

retain a solder plug after solidiﬁcation. Holes greater than

1.5 mm [0.0591 in] shall not be rejected for failure to

retain a full solder plug provided that the entire barrel of

the hole and the surface of the top land have been wetted

with solder (see Figures 4-5 and 4-6).

Preferred

Wetting

Small Amount

of Dewetting

Complete

Dewetting Nonwetting

IPC-003b-5-1

Figure 5-1 Aid to Evaluation

IPC J-STD-003B March 2007

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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6 NOTES

6.1 Correction for Buoyancy

For the wetting balance to

obtain wetting force values that are comparable with one

another, it is necessary to correct for the variability in test

specimen sizes, particularly width and thickness. This is

done by correcting for the volume of the sample immersed

in the solder. The following formula may be used to calcu-

late the buoyant force correction:

= ρ gV

where:

ρ = Density of solder at 235 °C (8.12 g/cm) for Sn60/

Pb40 Alloy

ρ = Density of solder at 255 °C (7.41 g/cm) for SAC305

Alloy

g = Acceleration of gravity (981 cm/sec

)

V = Immersed volume of the test specimen (cm

)

= width x thickness x immersion depth, for example.

When the buoyancy force is calculated, it should be used

to correct the zero axis. This correction is required to

obtain both the proper measurement of wetting times, as

well as wetting forces. All measurements of wetting times

and wetting forces must be made from the corrected zero

axis. In the case of an upright curve, the new corrected zero

axis will be below the instrumental zero.

6.2 Preheat If the board test specimen does not pass the

standard solderability test then a uniform preheat of a sec-

ond test specimen may be used to determine if design/

construction has impacted the solderability test (i.e., a thick

board with heavy internal ground planes). If this referee

test specimen passes, then testing with preheat shall be the

method of choice for future testing of test specimens hav-

ing that design/construction.

6.3 Baking The occurrence of outgassing, which may

result in blowholes, measling, blisters or delamination, may

be reduced by baking the printed board prior to soldering

to eliminate moisture or solvents. Other factors, such as

conveyor speed (for wave solder testing), solder tempera-

ture, contamination content, etc., may also cause defects

and, therefore, should be analyzed if problems occur. Test

specimens should be baked in a suitable oven to remove

any absorbed moisture. Temperature and time of baking is

to be determined on an individual basis.

The time between baking and solderability testing should

be kept to a minimum (not more than 24 hours) in order to

prevent re-absorption of water vapor into the laminate

structure. The actual time delay threshold is dependent

upon ambient temperature and humidity levels.

6.4 Prebaking Printed boards should be prebaked only if

prebaking is normally used as a production procedure.

Baking should be kept to a minimum, adhering to the pro-

duction procedure, to prevent excessive oxidation and

intermetallic growth.

6.5 Safety Note Care must be taken in both usage and

storage to keep ﬂammable solvents from sparks or ﬂames.

See the Material Safety Data Sheets (MSDS) for all sol-

vents. All chemicals shall be handled per appropriate data

sheets, and disposed of per local regulations.

6.6 Use of Nonactivated Flux This standard speciﬁes a

rosin-based ﬂux with a very speciﬁc quantity of activator.

The intent of requiring the use of a speciﬁc quantity of ﬂux

activator is to reduce the variability of test results that were

seen with pure rosin ﬂux, enable the solderability testing of

nontin component lead metallizations, and provide a realis-

tic solderability testing safety factor by keeping the amount

of activator both ﬁxed and less than that used for produc-

tion soldering. The beneﬁt of using this speciﬁed activated

solderability testing ﬂux composition was demonstrated by

extensive testing, as reported in the J-STD-002/003 Acti-

vated Solderability Test Flux Rationale Committee Letter.

6.7 Solder Contact The solder applied during the solder-

ability test must contact a feature in order for that feature

to be considered for evaluation. Small features surrounded

by a thick solder mask may prevent solder contact.

March 2007 IPC J-STD-003B

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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