IEC 60068 2 83 Edition 1 0 2011 09 INTERNATIONAL STANDARD NORME INTERNATIONALE Environmental testing – Part 2 83 Tests – Test Tf Solderability testing of electronic components for surface mounting dev[.]
General description
The specimen is securely positioned on a suitable holder and suspended from a sensitive balance It is then immersed in solder paste applied to the test jig plate, which is subsequently heated to melt the paste The vertical forces of buoyancy and surface tension, collectively referred to as the "acting force," act on the immersed specimen This force is measured by a sensor and continuously recorded or monitored over time.
NOTE The wetting force can be evaluated only for components of the same shape and size The absolute evaluation is not achieved by this method.
Test methods
There are three methods for evaluating the wettability of component electrodes, each specified in the relevant documentation The first method, the Quick Heating Method, involves immersing the specimen in solder paste before a rapid temperature rise melts the paste The second method, known as the Synchronous Method, requires the specimen to be immersed in solder paste at the onset of the temperature rise Lastly, the Temperature Profile Method utilizes a temperature profile similar to that used in production to melt the solder paste and assess the wettability of the component electrodes.
NOTE 1 This test (Tf) may be applicable to leaded SMD packages In order to achieve comparable and repeatable results, test Tf should be done on straight leads
NOTE 2 Solder paste to be used is not specified in this standard
Testing of components should be conducted on the specimens as received, ensuring they remain uncontaminated by fingers or other items If specified, specimens may be immersed in an organic solvent at room temperature to eliminate surface contaminants like grease No alternative cleaning methods are permitted, and cleaned specimens should be air-dried.
When accelerated ageing is prescribed by the relevant specification, one of the methods of
4.1.4 (Ageing 1) of IEC 60068-2-20:2008 shall be used The aging condition shall be specified in the relevant specification
Solder paste
To ensure optimal performance, use solder paste that has been stored in a sealed container in a dark environment at temperatures below 10 °C, avoiding direct sunlight exposure Proper preparation of the solder paste is crucial before conducting the test, allowing it to reach ambient conditions.
Maintain a temperature of 25 °C ± 5 °C and relative humidity of 50 % RH ± 10 % for 8 hours, or follow the manufacturer's data sheet Open the supply container(s), remove any internal covers, and scrape off any paste adhering to the lids, internal covers, and container walls, adding this material back into the supply container(s) Gently stir the paste with a spatula for 1 to 2 minutes to achieve homogenization, ensuring that no air is introduced.
If necessary, gently transfer the paste to a test container of sufficient volume, taking care to avoid the introduction of air.
Test jig plate
Test jig plates must be kept in a sealed container and cleaned with a dilute hydrochloric acid solution just before use Each test requires a new test jig plate, and any unused plates should be discarded rather than returned to the sealed container.
Specimen holder
To ensure optimal performance, it is essential to clean the specimen holder, as it can become contaminated by the flux used during testing Utilizing a neutral organic solvent for cleaning is recommended, and incorporating ultrasonic agitation can enhance the cleaning process.
Equipment
The equipment used for the quick heating method consists of a measurement, heating and lift system, as shown in Figure 1 The detailed requirements to the equipment are specified in
The measuring system includes a vertical force sensor, a signal transducer, and a recorder The heating system is designed to maintain a set temperature within ± 3 °C Additionally, the lift system is responsible for the immersion and withdrawal of the specimen as outlined in section 7.4.3.
1 Specimen 7 Holding jig of a test jig plate
5 Lift for test jig plate 11 Recorder
6 Lift for heating bath 12 Controller
Figure 1 – Examples of the quick heating method test equipment
Test jig plate
The test jig plate shall be as specified in Table 1
Table 1 – Specification of the test jig plate for quick heating and synchronous method
Item Specification of the test jig
Material Oxygen-free phosphate copper
Dimensions ( L , W ) Less than 30 mm one the side, or less than a total area of 900 mm 2
9 mm to 10 mm at the bottom,
13 mm to 14 mm at the top
Solder resist ( D 3 , D 4 ) Inner diameter of 10 mm ± 0,02 mm, and over 20 mm for the outer diameter
Resist coat thickness 0,035 mm ± 0,01 mm
Warp ± 0,05 mm (for the longer side for a rectangular shape)
An example of the test jig plate used in the quick heating and synchronous method is shown in Figure 2
1 Drawing for solder resist h Drawing depth
D 1 Outer diameter of drawing D 3 Inner diameter of solder resist
D 2 Inner diameter of drawing D 4 Outer diameter of solder resist
Figure 2 – Example of test jig plate for quick heating and synchronous method
Preparation
Test condition
Test temperature
The test jig plate shall be processed using the temperature profile as specified Figure 3 shows a typical example
Symbol SAC type Sn-Pb type
T 1 Solder melting temperature T 2 Test temperature t Test duration (5 s to15 s) t 1 Time from start to T 1 t 2 Time from start to T 2
The test starts at a temperature of 50 °C or less
Time from start to T 1 ( t 1 ) shall be 1,5 s or less
Time from start to T 2 ( t 2 ) shall be 3 s or less
The ramp down rate is not specified
Figure 3 – Example of the temperature profile
Feed of solder paste and immersion condition
The recommended condition of immersing a specimen into the solder paste is given in Table 2
For components not specified in Table 2, test conditions shall be specified in the relevant specification or agreed upon between the trading partners
Table 2 – Recommended test conditions of the quick heating and synchronous method for rectangular SMD
Sizes of specimen a Immersion depth b, c Angle and direction of specimen immersing into solder paste
The designation 3216 (1206) indicates a specimen measuring 1.0 mm in length and 0.5 mm in width, with the dimensions in parentheses provided in Imperial units Recommended immersion depths are listed in the table, as buoyancy force can vary based on the electrode configuration The specified immersion depth represents the target values.
Immersion and withdrawal conditions for test specimen
The immersion speed for the specimen into the solder paste should be between 0.5 mm/s and 1 mm/s, while the test jig should be immersed into the heating bath at a speed ranging from 1 mm/s to 5 mm/s.
Test procedure
Test procedure shall be as follows a) Apply solder paste to the test jig keeping the surface flat Figure 4 shows an example
2 Solder paste 4 Direction of squeeze movement
To apply solder paste to a test jig plate, first, mount the specimen into the clip until the specified angle is achieved Ensure the clip is centered on the upper surface of the test jig plate with the solder paste applied Before starting the test, adjust the force sensor and recorder outputs to zero Finally, immerse the specimen into the solder paste to the depth indicated in the guidelines.
Then, heat the jig plate to melt the solder paste in accordance with the temperature profile as specified in Figure 3
The specimen should be immersed in solder paste to a depth of at least twice the specified depth, followed by the specified depth itself This process is essential for applying flux to the part of the specimen that matches the immersion depth prior to heating.
Solder pasteRectangular SMD e) Withdraw the specimen from the molten solder paste when measurement is finished
Recording of the result is completed when the force reaches to a stable state or specified duration.
Presentation of the result
The recorder measures the force applied to the specimen in the vertical direction, with upward forces, such as pushing force or buoyancy, recorded as negative values, while downward forces, like wetting force, are recorded as positive values.
The output signal typically resembles the shape illustrated in Figure 5 For any discrepancies from this shape, please refer to Annex B for data interpretation and correction.
A ct ing f or ce P os itiv e N egat iv e
A 1 Reference point to start time measurement
NOTE Point A 1 is the first positive force peak during the test
B 1 Instance when the force curve crosses the zero line
C 1 Instance when the wetting force reaches to 2/3 of the maximum wetting force
D 1 Instance when the maximum force is obtained in the measurement
E 1 Instance when the specimen is withdrawn after the measurement is completed
In the F1 instance, the force stabilizes after the specimen is removed from the jig plate The time to start wetting, denoted as \( t_{01} \), is the duration from point \( A_1 \) to point \( B_1 \) The wetting time, represented as \( t_{11} \), measures the duration from point \( B_1 \) to point \( C_1 \).
F 1,max Maximum wetting force The maximum force obtained (the value from the zero line) in the measurement
F 1,end Final wetting force The force obtained (the value from the zero line) at the end of the test
Figure 5 – Typical output shape of signal in the quick heating method
Characterisation parameter examples
a) The time to start wetting: t 01 b) Wetting time: t 11 c) Maximum wetting force: F 1,max d) Wetting stability: Sb 1 ; The ratio of the final wetting force (F 1,end ) and the maximum wetting force (F 1,max )
NOTE Wetting stability is calculated from Sb 1 = F 1,end /F 1,max
Equipment
The equipment used for the synchronous method consists of measurement, heating and lift system as shown in Figure 6 The detailed requirements to the equipment are specified in
The measuring system includes a vertical force sensor, a signal transducer, and a recorder The heating system must maintain the set temperature within the tolerances outlined in section 8.5.1 Additionally, the lift system is designed for the immersion and withdrawal of the specimen as detailed in section 8.5.3 Finally, the synchronous fixturing system allows for the simultaneous immersion and heating of the specimen, as specified in section 8.6.
2 Test jig plate 9 Support bars with spring
Figure 6 – Example of synchronous method test equipment
Test jig plate
The test jig plate shall be as specified in Table 1
An example of the test jig plate used in the synchronous heating method is shown in Figure 2.
Synchronous fixture
An example of the synchronous fixture is shown below in Figure 7
Figure 7a – Test jig plate holder Figure 7b – Mini crucible
Figure 7 – Example of synchronous fixture
Preparation
Test condition
Test temperature
The test jig plate shall be processed using the temperature profile as specified Figure 3 shows a typical example.
Feed of solder paste and immersion condition
The recommended condition of immersing a specimen into the solder paste is given in Table 2
For component not specified in Table 2, test conditions shall be specified in the relevant specification or agreed upon between the trading partners.
Immersion and withdrawal conditions for the test specimen
The immersion speed of the specimen into the solder paste shall be 0,5 mm/s to 1 mm/s, and that of the mini crucible shall be 1 mm/s to 5 mm/s.
Test procedure
The test procedure involves several key steps: First, apply solder paste to the test jig while ensuring a flat surface, as illustrated in Figure 4 Next, mount the specimen into the clip until the specified angle in section 7.4.2 is achieved, ensuring the clip is centered on the test jig plate with solder paste Before starting the test, zero the output of the force sensor and recorder Then, attach the jig plate holder to the supporting bars, adjusting their height just above the solder paste near the electrode's bottom edge Heat the jig plate to melt the solder paste according to the temperature profile in Figure 3, synchronously bringing the specimen and solder paste into contact at the immersion speed specified in section 8.5.3 Finally, withdraw the specimen from the molten solder paste upon completion of the measurement.
Recording of the result is completed when the force reaches stable state or after a specified duration.
Presentation of the results
The recorder measures the force applied to the specimen in the vertical direction, with upward forces, such as pushing force or buoyancy, recorded as negative values, while downward forces, like wetting force, are recorded as positive values.
A typical shape of the output signal obtained is shown in Figure 8
P os itiv e N egat iv e A ct ing f or ce
A 2 Instance when the measurement starts The specimen is brought in contact with solder paste that is melting
B 2 Instance when the output crosses the zero line The downward force of the surface tension is exactly equal to the buoyancy force
C 2 Instance when the wetting force reaches 2/3 of the maximum wetting force
D 2 Instance when the maximum wetting force is obtained in the measurement
E 2 Instance when the specimen is withdrawn and the measurement is completed t 02 Time to start wetting Time duration from point A 2 to point B 2 t 12 Wetting time The time duration from point B 2 to C 2
F 2,max Maximum wetting force The maximum force optained (the value from the zero line) in the measurement
2/3 F 2,max 2/3 of the maximum wetting force
F 2 ,end Final wetting force The force obtained (the value from the zero line) at the end of the test
NOTE Certain solder pastes may cause an initial wetting (pull) force that may be attributed to the wetting agents contained in some solder pastes (see Annex E)
Figure 8 – Typical output shape of signal in the synchronous method
Characterisation parameter examples
a) The time to start wetting: t 02 b) Wetting time: t 12 c) Maximum wetting force: F 2,max d) Wetting stability: Sb 2 ; The ratio of the final wetting force (F 2,end ) and the maximum wetting force (F 2,max )
NOTE Wetting stability is calculated from Sb 2 =F 2,end /F 2,max
Equipment
The equipment for the temperature profile method consists of systems of measurement, heating, and mechanical lift An example of the measurement system is shown in Figure 9
The system requirements outlined in Annex C include a measuring system featuring a vertical force sensor, a mechanical-electrical signal converter, and recording equipment Additionally, the heating system must achieve the temperature profile detailed in section 9.4.1 Furthermore, the lift system should incorporate a mechanism capable of ascending and descending according to the conditions specified in section 9.4.3.
Figure 9 – Example of the system for temperature profile method test equipment
Test jig plate
The test jig plate shall be as specified in Table 3
Table 3 – Specification of the test jig plate of the temperature profile method
Item Specification of the test jig plate Material oxygen-free phosphate copper
Shape square or rectangular plate
Size 15 mm to 35 mm for each side
Warp ±0,05 mm (the longer side for a rectangular shape)
Preparation
Test condition
Test temperature
The test temperature refers to the temperature of the jig utilized during the testing process, and the jig plate must be processed according to the specified temperature profile, as illustrated in Figure 10.
Symbol SAC type a Sn-Pb type a
T 4 b 245 °C ± 3 °C 220 °C ± 3 °C a For example: SAC type (Sn96,5Ag3Cu,5), Sn-Pb type (Sn63Pb37) b T 4 is the preset temperature of the heating unit The jig temperature may not reach the preset temperature
T 3 Pre-heating temperature t 3 Pre-heating duration
T 4 Peak temperature The measurement starts at a temperature of 50 °C or less
The ramp down rate is not specified
Figure 10 – Example of the temperature profile
Feed of solder paste and immersion condition
Table 4 outlines the recommended solder paste quantity and the immersion conditions for specimens during soldering tests For components not listed in Table 4, the testing conditions must be defined in the relevant specifications or mutually agreed upon by the trading partners.
Table 4 – Recommended test conditions of the temperature profile method for rectangular SMD
Types and sizes of specimens a
Amount of solder paste applied b , c
Angle and direction of specimen immersing into solder paste
3216 (1206) a Designation of the size, for example 1005, means a specimen with a length of 1,0 mm and a width of
The dimensions are specified as 0.5 mm (in Imperial units) The quantity of solder paste applied is determined by the size of the specimen, with target values set for both the amount of solder paste and the immersion depth.
Immersion and withdrawal conditions for test specimen
The specimen is immersed in the unfused solder paste to cover the test area with the paste
During the temperature ramp-up, the specimen is removed from the solder paste to effectively separate the cohesive forces of the solder paste from the wetting forces acting between the specimen and the solder.
The separation timing occurs 0.5 seconds before the acting force drops to zero, as indicated by the gradient after the force peaks Following this 0.5-second interval, the specimen is detached from the solder paste and subsequently re-immersed, returning to its original position.
The speed of withdrawal and re-immersion of the specimen to and from the solder paste shall be 5 mm/s ± 0,5 mm/s.
Test procedure
The test procedure involves applying a specified amount of solder paste, as outlined in section 9.4.2, onto a cleaned test jig plate This is achieved using a stainless steel mask and a stainless steel or urethane squeegee, as illustrated in Figure 11.
2 Metal mask 4 Direction of squeeze movement
Figure 11 – Example of applying solder paste to a test jig plate b) Fix the specimen on the holder designed to realize the immersion angle specified in 9.4.2
Position the holder at the center of the test jig plate and ensure the force sensor output is set to zero before immersing the specimen in solder paste, following the immersion conditions specified in section 9.4.2 Heat the jig plate to melt the solder paste according to the temperature profile in Figure 10, and withdraw the specimen during the temperature ramp-up Immerse the specimen in the solder paste again just before the solder reaches its liquidus temperature, approximately 217 °C for SAC type solder paste and 183 °C for Sn-Pb type solder paste Finally, withdraw the specimen from the molten solder paste once the measurement is complete.
The recorder will capture the force signal from the transducer between points A'' 3 and F 3, as illustrated in Figure 12 The measurement concludes once the force stabilizes or after a predetermined duration.
Presentation of the result
Figure 12 illustrates the typical output signal shape as the sample temperature increases according to the defined temperature profile Annex C provides the interpretation and correction for any data that deviates from the shape depicted in Figure 12.
The data for the period between A 3 and A'' 3 are not used in the evaluation of wetting force of the specimen
NOTE The upward force as shown in Figure 12 with a dotted line between A' 3 and A'' 3 is the coagulation force when the solder paste melts
10 s ± 0,5 s A ct ing f orc e P os itiv e N egat iv e
A 3 The instance the test jig starts to heat
A’ 3 Instance when the flux in the solder starts to melt
A’’ 3 Instance when the wetting of the solder to the specimen starts
C 3 Instance when the wetting force reaches 2/3 of the maximum wetting force c 3 Instance when the wetting force reaches 86 % of the maximum wetting force
D 3 Instance when the maximum wetting force is obtained in the measurement
E 3 Instance when the specimen is withdrawn after the measurement is completed
The F 3 instance occurs when the force stabilizes after the specimen is removed from the jig plate The wetting time at t 13, which is two-thirds of the total duration, is measured between point C 3 and point A’’ 3 Additionally, the wetting time at t 23, representing 86% of the total duration, is also calculated between point C 3 and point A’’ 3.
F 3,max Maximum wetting force The maximum force obtained (the value from the zero line) in the measurement
F 3,end Final wetting force The force obtained (the value from the zero line) at the end of the test
Figure 12 – Typical output shape of signal in the temperature profile method
Characterisation parameter examples
a) Wetting time: t 13 and/or t 23 b) Maximum wetting force: F 3,max c) Wetting stability: Sb 3 ; The ratio of the final wetting force (F 3,end ) and the maximum wetting force (F 3,max )
NOTE Wetting stability is calculated from: Sb 3 = F 3,end / F 3,max
Equipment for the quick heating and synchronous method
This annex specifies the details of the test equipment for the quick heating and synchronous method
The details of the test equipment are specified as follows
The measuring system must meet specific criteria: it should measure wetting forces within a range of -10 mN to +10 mN, have a displacement sensitivity exceeding 0.5 mN/µm, and a resolution better than 0.01 mN Additionally, the system must continuously record output signals covering the range from A1 to F1 of the provided data.
The recorder must be capable of recording output data on a recording sheet or displaying it via a personal computer It should achieve a time resolution of better than 0.1 seconds Additionally, the response time of the recording tip must be less than 0.3 seconds to return from the maximum output to the zero center, with an overshoot of less than 1% of the reading Furthermore, the electrical and mechanical noise levels in the system should not exceed 10% of the signal.
The heating system shall comply with the following requirements a) The heating section of the system shall realize the temperature profile as specified in
The heating bath must have a diameter greater than 50 mm and a depth exceeding 15 mm, while the inner diameter of the mini crucible used for the synchronous method should be 25 mm.
The lift system must meet specific criteria, including the ability to adjust the immersion depth of the specimen into the solder paste on the test jig plate in increments of 0.05 mm, with a maximum depth corresponding to the drawing depth of the test jig plate Additionally, the position resolution should be controllable to better than 0.02 mm Furthermore, the system must be capable of immersing both the specimen in solder paste and the test jig into the heating bath, as outlined in section 7.4.3.
Reading of the output data and correction of the result in the quick heating test
This annex specifies the reading of the output data and correction of the result other than as shown Figure 5
B.2 Reading of the output form in the quick heating test
Figure B.1 presents additional typical examples, where the bold line illustrates the force applied to a specimen over time, while the fine horizontal line indicates the zero line Notably, point B1 marks the moment when the force line intersects the zero line.
In cases where the force line does not intersect the zero line, it is impossible to determine B 1, as well as the initial wetting time, t 01, and the total wetting time, t 11 To derive a virtual B 1, one must identify the intersection point between an extended supplemental line and the zero line on the chart.
B 1 for the cases a) to c) and g) is the B 1 as given in the figures The correction for the cases of d) to f) in Figure B.1 shall be made in accordance with B.3
B 1 for case h) in Figure B.1 cannot be obtained b) Maximum wetting force, F 1,max :
F 1,max for the cases a) to d) is the F 1,max as given in the figures The correction for the cases of e) to g) in Figure B.1 shall be made in accordance with B.3
In the scenario depicted in Figure B.1, the maximum wetting force, denoted as F 1,max, cannot be determined Initially, wetting initiates from a negative force applied to the specimen Following this, a peak wetting force is observed, which subsequently diminishes over time Additionally, a significant step in the wetting process is noted.
The initial step, denoted as “F_a,” exceeds 0.5 times the maximum wetting force, “F_{1,max}.” In contrast, when “F_a” is 0.5 times “F_{1,max}” or lower, it indicates an apparent maximum wetting force Following this, the force diminishes from the apparent maximum wetting force until it approaches zero, ultimately resulting in a negative force.
Figure B.1 – Typical wetting force changes in quick heating method
B.3 Correction to the typical data attained by the quick heating method
Corrections to experimentally obtained data are necessary in specific scenarios One such case involves adjusting the initial wetting time when the wetting force exhibits a step-wise change, as illustrated in Figures B.1c and B.1d To accurately determine the initial wetting time, denoted as \$t_{01}\$, the correction should be based on either Figure B.2 or Figure B.3, depending on whether the wetting force value is greater or less than a certain threshold.
1/2 of the maximum wetting force
1) The wetting force at the first step, F a , is larger than 0,5 F 1,max (applicable to
The start of wetting of the first step is taken as the initial time of wetting, B 1
Figure B.2 – Example of correction of the initial time of wetting ( F a is larger than 0,5 F 1,max )
2) The wetting force at the first step, F a , is 0,5F 1,max or less (applicable to Figure B.1, d))
Draw a tangential line to the wetting curve and obtain the crossing of this tangential line and the zero line to obtain the initial time of wetting, B’ 1
Tangential line to the wetting B' 1
In Figure B.3, we illustrate the correction of the initial wetting time when the force \( F_a \) is 0.5 times \( F_{1,max} \) or lower Additionally, this correction applies to scenarios where a distinct positive peak is observed in the wetting process, as depicted in Figures B.1e to g.
1) Correction to the initial time of wetting (applicable to Figure B.1, e) to f)
Draw a tangential line to the wetting curve (refer to Figure B.3) and obtain the crossing of this tangential line and the zero line to obtain the initial time of wetting, B’ 1
2) Correction to the maximum wetting force (applicable to Figure B.1, e) to g)
The maximum wetting force is the force when wetting has reached stable state
The time to reach 2/3 of the maximum wetting force (refer to C 1 in Figure 5) is obtained from the corrected maximum wetting force
Test equipment for the temperature profile method
This annex specifies the details of the test equipment for the temperature profile method
The details of the test equipment are specified as follows
The measuring system must meet specific criteria: it should measure wetting forces within a range of -10 mN to +10 mN, have a displacement sensitivity exceeding 0.5 mN/µm, and a resolution better than 0.01 mN Additionally, the system must continuously record output signals covering the range from A’’ 3 to F 3 of the provided data.
The recorder must be capable of recording output data on a recording sheet or displaying it via a personal computer It should have a time resolution of better than 0.1 seconds and a response time of the recording tip that is less than 0.3 seconds to return to the zero center, with an overshoot of less than 1% of the reading Additionally, the system's electrical and mechanical noise must not exceed 10% of the signal.
The heating system shall comply with the following requirements a) The heating section of the system shall realize the temperature profile as specified in
Figure 10 b) The temperature difference between the solder paste and the electrodes of testing specimen shall be less than 5 °C for the temperature of solder paste of 212 °C to 222 °C
The standard specifies that the melting point of SAC solder ranges from 178 °C to 188 °C for Sn-Pb solder It is important to note that a temperature difference of up to 10 °C may occur if the solder paste temperature falls outside this range However, the standard does not address the temperature difference resulting from the latent heat of the solder paste.
The lift system must meet specific criteria, including an immersion and withdrawal speed ranging from 0.5 mm/s to 5 mm/s, and a position resolution that can be controlled to better than 0.01 mm Additionally, the system should effectively immerse a specimen in solder paste and facilitate its withdrawal, as outlined in section 9.5.
Reading of the output data and correction of the result in the temperature profile test
This annex specifies the reading of the output data and correction of the result other than as shown in Figure 12
D.2 Reading of the output form in the temperature profile test
Figure D.1 presents additional typical examples beyond those illustrated in Figure 12 The bold line represents the force applied to a specimen over time, while the horizontal fine line indicates the zero line The wetting time and the maximum force value, F 3,max, are utilized for cases a), b), and e) to f) as depicted in Figure D.1.
The correction for the case of c) in Figure D.1 shall be made in accordance with Clause D.3