IPC J-STD-003B - 第35页

APPENDIX B Calculation of Area Under the Wetting Curve The area is calculated using the maximum theoretical force (see Figure 4.10 or 4.1 1). Therefore, the area is given as: Area = W etting force x time - Buoyancy x tim…

APPENDIX A

Calculation of Maximum Theoretical

Force for a Rectangular Cross-Section

Maximum theoretical force for the test board with a ground

plane surface is calculated using the procedure of Klein

Wassink.

The maximum force, in units of milliNewtons

(mN), is deﬁned as:

Force (Max. Theoretical) = (γ) (P) (cosine β) - (d)(g)(V) =

[0.4P - 0.08V] mN

where:

P = The perimeter of the test specimen in millimeters, i.e.,

the length in millimeters of the solder/printed board or

coupon pad (or hole)/air interface as measured at

maximum depth of immersion.

V = The volume in cubic millimeters of the test specimen

that resides below the solder/board air interface as

measured at the maximum depth of immersion.

γ = Surface tension of solder = 0.4 mN/mm

γ = Surface tension of Pbfree solder = 0.5 mN/mm

α = Immersion angle of the board to the horizontal surface,

i.e., α =45°

β = Wetting angle of solder to the board under optimal

conditions, i.e., β = 0, Therefore the cosine β =1

d = Density of solder at 235 °C, = 8120 kg/m

for Sn60/

Pb40 Alloy

d = Density of solder at 255 °C = 7410 kg/m

for SAC305

Alloy

g = Gravitational constant = 9.8 x 10

mm/s

Periphery and volumes Perimeter and volumes are to be

calculated using the nominal values provided by the test

board supplier and the angles and depths of immersion as

described in the speciﬁcation above. The TOTAL perimeter

(the length in millimeters of all of the solder/coupon or

coupon/pad (or hole)/air interfaces on the test coupon being

immersed (e.g., if there are ﬁve pads being immersed, then

the sum of the widths of the ﬁve pads parallel to the solder

surface) is to be used. For the immersion volume, use the

volume of the portion of the test coupon pushed below the

surface of the solder and NOT the entire volume of the

whole test coupon, is to be used in this calculation. Where:

For Example:

For a tin/lead solder alloy:

Width of coupon = 0.4 mm, Length = 9.2 mm, P = wetting

perimeter = 10 mm, Immersion depth=D=0.2mm

Hence for a dip at a 90 ° angle:

V = Total volume immersed = (10 - (2 x 0.4)) mm x

0.2 mm x 0.4 mm = 0.736 mm

Therefore, the maximum theoretical wetting force is:

Maximum Force = (γ) (P) (cosine b) - (d) (g) (V) =

(0.4 mN/mm x 10 mm x cosine 0) - (8.12 x 10-6 kg/mm

x 9.8 x 103 mm/s

x 0.736 mm

) = 3.94 mN

Finally, for a 10 mm perimeter, ideal wetting force per mil-

limeter of perimeter for our sample is 0.394 mN/mm. From

Table 4.5 (or 4.6) the force measured on a test specimen in

the ‘‘preferred’’ class must be close to 0.394 mN/mm. (It

CANNOT be greater than 0.394 mN/mm.)

Theoretical force calculations are difficult for test speci-

mens with other than pads that come to the edge of the

specimen. Therefore, the best way to use the wetting bal-

ance test method is to separately set up a control value for

a ‘‘Best Possible’’ sample; and other test pieces will be

compared to this value for establishing either an acceptable

or a reject criterion.

Second Example:

The calculations for the same sample dipped into the same

solder at a 45 angle

For a tin/lead solder alloy:

Width of coupon = 0.4 mm, Length = 9.2 mm, Immersion

depth=D=0.2mm,P=wetting perimeter = 10 mm

Hence for a dip at a 45 ° angle:

V = Total volume immersed = 0.5 x 9.2 mm x 0.283 mm

x 0.283 mm = 0.368 mm

(The 0.5 accounts for the fact that you are only dipping at

a 45 ° angle). Remember the area of a right angle triangle

is one half times the length of the two sides that are not the

hypotenuse.) Still assuming perfect wetting (wetting angle

= 0 °) Cosine of0°=1

Therefore, the maximum theoretical wetting force is:

Maximum Force = (γ) (P) (cosine b) - (d) (g) (V) =

(0.4 mN/mm x 10 mm x cosine 0) - (8.12 x 10

-6

kg/mm

x9.8x10

mm/s

x 0.368 mm

) = 3.97 mN

Therefore, again for a 10 mm perimeter, ideal wetting force

per millimeter of perimeter for our sample 0.397 mN/mm,

slightly higher than in the previous example because the

buoyancy correction is only half the size.

2. R.J. Klein Wassink, ‘‘Soldering in Electronics,’’ 2nd Edition, Electrochemical Publications, Ayr, Scotland, 1989, pp 308-309

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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APPENDIX B

Calculation of Area Under the Wetting Curve

The area is calculated using the maximum theoretical force

(see Figure 4.10 or 4.11). Therefore, the area is given as:

Area = Wetting force x time - Buoyancy x time

Area = (3.0 sec. x Max. Theoretical Force) -

2.0 sec (ρ) (g) V

Area = (3.0 sec. x Max. Theoretical Force) -

2.0 sec x - (8.12 x 10

-6

kg/mm

9.8x10

mm/s

xV)

The value V is the volume of the test specimen immersed

in the solder bath as calculated in Appendix A. The maxi-

mum theoretical force is calculated as per Appendix A. The

following assumptions are made:

1. The maximum buoyancy force holds for the whole two

(2) seconds contributing a negative area of: the buoy-

ancy force times two (2) seconds.

2. The test specimen essentially attains the full maximum

theoretical force as it crosses the zero line at two (2)

seconds and holds that value for the duration of the test,

i.e., three (3) seconds.

V = Total Volume = 0.4 mm

Maximum Theoretical Force: 3.97 mN

Area = (3.0 sec. x 3.97 mN) - (2.0 sec. x 0.08 (kg/mm

mm/s

) x 0.4 mm

) = 11.91 mN x seconds - 0.064

(kgmm/sec)

Since F = ma, then mN = kg x mm/sec

kg = mNsec

/mm

Area = 11.91 mN x seconds - 0.064 (mNsec

/mm) x

(mm/sec)

Area = 11.91 mN x seconds - 0.064 mN x seconds

Area = 11.85 mN x seconds

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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APPENDIX C

Informative Annex

C.1 Test Equipment Sources

The equipment sources described below represent those

currently known to the industry. Users of this document are

urged to submit additional source names as they become

available, so that this list can be kept as current as possible.

C.1.1 Edge Dip Solderability Test Apparatus

GEN3 Systems Limited (Formerly Concoat Systems) Unit

B2, Armstrong Mall, Southwood Business Park, Farnbor-

ough, Hampshire GU14 0NR England. 011 44 12 5252

1500, www.gen3systems.com

HMP Soldermatics, P.O. Box 948, Canon City, CO 81212,

(719) 275-1531.

Robotic Process Systems, 23301 E. Mission Ave., Liberty

Lake, WA 99019, (509) 891-1680.

Solderability Testing and Solutions Inc., 18 Wildrose Dr.,

Edgewood, KY 41017, (859) 331-0598), www.wetting-

balance.com

C.1.2 Rotary Dip Test Apparatus

Robotic Process Systems, 23301 E. Mission Ave., Liberty

Lake, WA 99019, (509) 891-1680.

C.1.3 Wetting Balance Test Apparatus

GEN3 Systems Limited (Formerly Concoat Systems) Unit

B2, Armstrong Mall, Southwood Business Park, Farnbor-

ough, Hampshire GU14 0NR England. 011 44 12 5252

1500, www.gen3systems.com

Malcomtech 26200 Industrial Blvd, Hayward CA 64545,

510-293-0580, www.malcomtech.com

Metronelec, 54, Route de Sartrouville - Le Montreal 78232

Le PECO Cedax, France (USA Distributor/Solderability

Testing and Solutions Inc., 18 Wildrose Dr., Edgewood,

KY 41017, (859) 331-0598), www.wettingbalance.com

Robotic Process Systems, 23301 E. Mission Ave., Liberty

Lake, WA 99019, (509) 891-1680.

C.2 Consumable Product Sources

C.2.1 Test Flux Product Sources

The Test Flux product sources described below represent

those currently known to the industry. Users of this docu-

ment are urged to submit additional product source names

as they become available, so that this list can be kept as

current as possible.

AIM Solder {www.aimsolder.com} - Standard Flux #1

Product ID: RMA 202-25

GEN3 Systems Limited {www.gen3systems.com} - Prod-

uct ID’s: SMNA - Standard Flux #1: Actiec2/-Standard

Flux #2: Actiec 5

Kester {www.kester.com} - Standard Flux #1 Product ID:

182

Qualitek International, Inc. {www.qualitek.com} - Stan-

dard Flux #1 Product ID: 285-25

Solderability Testing and Solutions Inc. {www.wettingbal-

ance.com} - Standard test ﬂux 0.2% and Standard test ﬂux

0.5%

C.2.2 Gage R&R Test Coupon Product Sources

The copper coupons required for the Gage R&R testing in

Appendix D shall be acid copper electroplated foil, HTE

grade (conforms to IPC-4562/3 - CU-E3), but they shall

have NO conversion coatings applied.

(NOTE: The coupons will/should look stained and oxi-

dized.)

The copper coupon can be of any of the three following

dimensions, AABUS:

• 10 mm x 10 mm X 35µµm thick foil (1 oz nominal)

• 5 mm x 10 mm x 35 µm thick foil (1 oz nominal)

• 2 mm X 10 mm X 35 µm thick foil (1 oz nominal)

Solderability Testing and Solutions Inc. {www.wettingbal-

ance.com} is one source of these Gage R&R test coupons.

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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