IEC 60068 2 58 Edition 4 0 201 5 03 INTERNATIONAL STANDARD NORME INTERNATIONALE Environmental testing – Part 2 58 Tests – Test Td Test methods for solderability, resistance to dissolution of metalliza[.]
Wetting
In various specifications, a complete or nearly complete solder coating is often defined by the 95% requirement This requirement can be challenging to apply when assessing specimens with metallized or short metallic terminations, particularly when different parts of the termination are identified Despite these challenges, the same evaluation approach is utilized To aid in the assessment of wetting, the photographs in Figure A.1 have been scaled to ensure that dimensions are comparable to those observed under a microscope, while still maintaining clarity for smaller details.
Evaluation of wetting
Acceptable when 95 % or more area to be evaluated covered by an ideal solder coating with a dewetting area shall be scattered and not concentrated in one area
Figure A.1 comprises six examples illustrating the criteria for visual examination
The ideal coating should be applied uniformly on both the foot and sides, ensuring that the visible rim remains intact without any dewetting due to the absence of a contact angle Additionally, it is important to ensure that the flux residues between the body and termination are properly removed.
U nacceptabl e: more than 5 % d ewetti ng on the toe; the bend i s wel l coated
Acceptable: some spots of non -i d eal coating on the su rface are visibl e U nacceptabl e: more than 5 % of the foot is dewetted
Acceptable: a few very small irregu l ariti es are visi bl e U nacceptabl e: more than 5 % of the area is not wetted
N OTE Th e arrows indicate imperfections (acceptable or unacceptable) referred to i n Cl au se A 2.
Evaluation of method 2 (Td1 )
For method 2 (reflow), solder balls at the pins or irregular solder accumulations are not allowed
The surface shall be homogenous without irregularities or damages
The results shall be documented in the test report including pictures.
Evaluation of method 2 (Td3)
General
Solderability testing should be conducted in a quantitative and objective manner The development of this standard has taken into account procedures that fulfill these criteria, which are detailed in IEC 60068-2-69.
I n choosing these conditions, consideration has been given to established procedures 1 , as well as the solder bath dip or reflow test conditions already specified in I EC 60068-2-20 and
For PCB components designed for bottom-side mounting and full immersion in wave soldering, the solder bath method (attitude A) is recommended It is essential to consider the relationship between static solder dip conditions and dynamic wave soldering conditions, as wave soldering presents more challenging conditions for components than static dipping.
The reflow method has been included for SMDs that are intended for the reflow process only, or to determine the suitability of an SMD for reflow
When selecting reflow profiles and peak reflow temperatures, it is crucial to exercise caution, as certain components may be damaged by the reflow temperature profile For instance, semiconductor devices must be handled carefully to ensure that their moisture sensitivity level (MSL) ratings are not surpassed, in accordance with IEC 60749-20 and IEC 61760-4 standards.
Limitations
Specimens with terminations coated in pure tin or other lead-free platings may exhibit discrepancies between dip test results in lead-tin solder baths and actual performance when using methods that operate below tin's melting point, such as vapor phase Currently, there is no known solution to this issue In these instances, standard production methods or the reflow method can be employed as alternative testing procedures.
B.2.2 Excessive peak reflow temperatures initiate failures, which cause equipment failures under normal use conditions
Solder dipping should be employed only when there is evidence demonstrating that the junction temperature of the part during wave soldering is comparable to that of dipping Furthermore, it is essential to have data indicating the appropriate preheating conditions to establish this correlation.
Preheating is extremely important to prevent damage to parts, especially to large volume packages Preheating is part of a good process set-up.
Choice of severity
Test Td1 : Solderability by solder bath method
The selection of time and temperature values from Table 3 depends on the thermal capacity of the components a) Low thermal capacity and/or high heat resistance component
1 These procedures have been established by TC 40 and TC 47, by I ECQ: IEC Quality Assessment System for
El ectronic Components http: //www i ecq org /ind ex htm and by the AI E: I ntern ation al Associ ati on Of Electri cal Contractors
I n Group 2, test condition 235 ° C, 2 s is preferred for general components of low thermal capacity b) For high thermal capacity component
For components having a high thermal capacity the relevant specification may prescribe an extension of the immersion time up to (1 0 ± 1 ) s
I n case of high thermal capacity components with lead, attitude B (floating attitude) or using separated lead should be chosen to avoid drop in solder bath temperature.
Test Td2: Resistance to soldering heat – Solder bath method
The selection of time and temperature values from Table 6 depends on the thermal capacity and thermal sensitivity of the components a) Low thermal capacity and/or high heat resistance component
I n group 2 and 3, test condition 260 ° C, 1 0 s is preferred for general components of low thermal capacity and high heat resistance b) For high thermal capacity component
Some soldering techniques necessitate a temperature of (270 ± 3) °C for (5 ± 0.5) seconds, or under more extreme conditions, for (10 ± 1) seconds These specific requirements should be outlined in the detail specification or mutually agreed upon by the trading partners.
The solder bath method is unsuitable for large semiconductor packages intended for reflow soldering due to its higher temperature compared to reflow soldering Additionally, this method is not recommended for components with low heat resistance.
I n case of aluminium electrolytic capacitors with non-solid electrolyte, film dielectric capacitors and connectors, the solder bath method cannot be applied.
Test Td2: Resistance to soldering heat –Reflow method
The selection of time and temperature values from Table 7 depends on the thermal capacity and thermal sensitivity of the components a) Low thermal capacity and/or high heat resistance component
The test conditions in Table B.1 are preferred for general components of low thermal capacity and high heat resistance
3 Sn 96, 5Ag3Cu, 5 1 50 200 21 7 260 30 ± 1 480 max b) H igh thermal capacity component
For components with high thermal capacity, the temperatures and times specified in Table 7 may not be suitable, as achieving T4 may be impossible In these situations, it is essential to determine t1, t2, and t4 in a way that ensures t3 is reached.
For plastic molded semiconductors, refer to I EC 60749-20 c) For a low heat resistance component
Temperature and time need to be selected from Table 7 depending on the heat resistance of a component as given by the relevant specification
For example, in case of aluminium electrolytic capacitors with non-solid electrolyte, the inner electrolyte temperature needs to be kept under the boiling point (e.g 21 0 ° C)
I mmersion attitude
The selection of the immersion attitude in Figure 1 and Figure 3 depends on the thermal capacity of the components a) For solderability of the termination
When evaluating the solderability of terminations, large flat specimens, such as ceramic chip carriers, can absorb heat when immersed in the solder bath In these instances, the floating attitude (attitude B) should be specified It is not advisable to differentiate between various specimen sizes by altering the immersion time Additionally, resistance to soldering heat is a critical factor to consider.
When testing resistance to soldering heat, large flat specimens like ceramic chip carriers should be positioned in a floating attitude to accurately reflect practical soldering conditions Immersing these specimens vertically does not create the necessary thermal gradient across their thickness Additionally, varying immersion times to differentiate between specimen sizes is not recommended.
Test Td3: Dewetting and resistance to dissolution of metallization for
In wave soldering, the dissolution rate of metallization significantly exceeds that of static dip methods Techniques such as wave, reflow, or vapor-phase soldering allow for additional iron soldering for repairs or touch-ups Consequently, a prolonged immersion at elevated temperatures is necessary to evaluate the metallization's resistance to dissolution in molten solder.
The severities of dewetting and resistance to dissolution of metallization shall depend on the components electrode structure
Solderability
The solderability of components designed for Through-Hole Reflow (THR) must be evaluated in accordance with IEC 60068-2-20, Test Ta, method 1, while adhering to the specific conditions outlined in Table C.1, which differ from those in the standard to better simulate reflow soldering conditions The relevant specification should include a preheating requirement prior to immersion in the solder bath, typically involving positioning the test specimen 10 mm above the solder bath surface for 30 seconds.
Table C.1 – Test conditions for solderability test
Sn96, 5Ag3Cu , 5 235 °C, (5 ± 0, 5) s recommend ed
Resistance to soldering heat
Test Td 2 , method 2, reflow simulation without solder shall be used The test conditions related to the respective soldering process group apply.
Dewetting
Test Td 3 , method 2, reflow simulation without solder shall be used The test conditions related to the respective soldering process group apply.
informative) Cross reference for references to the prior revision of this
In various specifications, a complete or nearly complete solder coating is often defined by the 95% requirement, which can be challenging to apply when assessing specimens with metallized or short metallic terminations Despite these difficulties, the same evaluation approach is utilized To aid in the assessment of wetting, the photographs in Figure A.1 have been scaled to ensure that dimensions are comparable to those observed under a microscope, while still maintaining clarity for smaller details.
Acceptable when 95 % or more area to be evaluated covered by an ideal solder coating with a dewetting area shall be scattered and not concentrated in one area
Figure A.1 comprises six examples illustrating the criteria for visual examination
The ideal coating should be uniform on both the foot and sides, ensuring that the visible rim remains intact without any dewetting due to the absence of a contact angle Additionally, it is important to note that the flux residues between the body and termination have not been eliminated.
U nacceptabl e: more than 5 % d ewetti ng on the toe; the bend i s wel l coated
Acceptable: some spots of non -i d eal coating on the su rface are visibl e U nacceptabl e: more than 5 % of the foot is dewetted
Acceptable: a few very small irregu l ariti es are visi bl e U nacceptabl e: more than 5 % of the area is not wetted
N OTE Th e arrows indicate imperfections (acceptable or unacceptable) referred to i n Cl au se A 2
Figure A.1 – Evaluation of wetting A.3 Evaluation of method 2 (Td 1 )
For method 2 (reflow), solder balls at the pins or irregular solder accumulations are not allowed
The surface shall be homogenous without irregularities or damages
The results shall be documented in the test report including pictures
Solderability testing should be conducted in a quantitative and objective manner The development of this standard has taken into account procedures that fulfill these criteria, which are detailed in IEC 60068-2-69.
I n choosing these conditions, consideration has been given to established procedures 1 , as well as the solder bath dip or reflow test conditions already specified in I EC 60068-2-20 and
For PCB bottom-side mounting and full body immersion during wave soldering, the solder bath method (attitude A) is preferred It is essential to consider the correlation between static solder dip conditions and dynamic wave soldering conditions, as wave soldering subjects components to more severe conditions than static dipping.
The reflow method has been included for SMDs that are intended for the reflow process only, or to determine the suitability of an SMD for reflow
When selecting reflow profiles and peak reflow temperatures, it is crucial to exercise caution, as certain components may be damaged by the reflow temperature profile For instance, semiconductor devices must adhere to their moisture sensitivity level (MSL) ratings to prevent exceeding limits, as outlined in IEC 60749-20 and IEC 61760-4.
Specimens with terminations plated in pure tin or other lead-free materials may show discrepancies between dip test results in lead-tin solder baths and actual performance in lower-temperature methods, such as vapor phase Currently, there is no known solution to this issue In these instances, standard production methods or the reflow method can be employed as alternative testing procedures.
B.2.2 Excessive peak reflow temperatures initiate failures, which cause equipment failures under normal use conditions
Solder dipping should be employed only when there is evidence demonstrating that the junction temperature of the part during wave soldering is comparable to that during dipping Furthermore, it is essential to have data indicating the appropriate preheating conditions to establish this correlation.
Preheating is extremely important to prevent damage to parts, especially to large volume packages Preheating is part of a good process set-up
B.3.1 Test Td 1 : Solderability by solder bath method
The selection of time and temperature values from Table 3 depends on the thermal capacity of the components a) Low thermal capacity and/or high heat resistance component
1 These procedures have been established by TC 40 and TC 47, by I ECQ: IEC Quality Assessment System for
El ectronic Components http: //www i ecq org /ind ex htm and by the AI E: I ntern ation al Associ ati on Of Electri cal Contractors
I n Group 2, test condition 235 ° C, 2 s is preferred for general components of low thermal capacity b) For high thermal capacity component
For components having a high thermal capacity the relevant specification may prescribe an extension of the immersion time up to (1 0 ± 1 ) s
I n case of high thermal capacity components with lead, attitude B (floating attitude) or using separated lead should be chosen to avoid drop in solder bath temperature
B.3.2 Test Td 2 : Resistance to soldering heat – Solder bath method
The selection of time and temperature values from Table 6 depends on the thermal capacity and thermal sensitivity of the components a) Low thermal capacity and/or high heat resistance component
I n group 2 and 3, test condition 260 ° C, 1 0 s is preferred for general components of low thermal capacity and high heat resistance b) For high thermal capacity component
Some soldering techniques necessitate a higher temperature of (270 ± 3) °C for a duration of (5 ± 0.5) seconds, or under more extreme conditions for (10 ± 1) seconds These specific requirements should be outlined in the detailed specifications or mutually agreed upon by the trading partners.
The solder bath method is unsuitable for large semiconductor packages intended for reflow soldering due to its higher temperature compared to reflow soldering Additionally, this method is not recommended for components with low heat resistance.
I n case of aluminium electrolytic capacitors with non-solid electrolyte, film dielectric capacitors and connectors, the solder bath method cannot be applied
B.3.3 Test Td 2 : Resistance to soldering heat –Reflow method
The selection of time and temperature values from Table 7 depends on the thermal capacity and thermal sensitivity of the components a) Low thermal capacity and/or high heat resistance component
The test conditions in Table B.1 are preferred for general components of low thermal capacity and high heat resistance
3 Sn 96, 5Ag3Cu, 5 1 50 200 21 7 260 30 ± 1 480 max b) H igh thermal capacity component
For components with high thermal capacity, the temperatures and times specified in Table 7 may not be suitable, as achieving T4 may be impossible In these situations, it is essential to determine t1, t2, and t4 in a way that ensures t3 is reached.
For plastic molded semiconductors, refer to I EC 60749-20 c) For a low heat resistance component
Temperature and time need to be selected from Table 7 depending on the heat resistance of a component as given by the relevant specification
For example, in case of aluminium electrolytic capacitors with non-solid electrolyte, the inner electrolyte temperature needs to be kept under the boiling point (e.g 21 0 ° C)
The selection of the immersion attitude in Figure 1 and Figure 3 depends on the thermal capacity of the components a) For solderability of the termination
When evaluating the solderability of terminations, large flat specimens like ceramic chip carriers can absorb heat when immersed in the solder bath In these instances, the floating attitude (attitude B) should be specified It is not advisable to differentiate between various specimen sizes by altering the immersion time Additionally, resistance to soldering heat is a critical factor to consider.
When testing resistance to soldering heat, large flat specimens like ceramic chip carriers should be positioned in a floating attitude to accurately reflect practical soldering conditions Immersing these specimens vertically does not create the necessary thermal gradient across their thickness Additionally, varying immersion times to differentiate between specimen sizes is not recommended.
B.3.5 Test Td 3 : Dewetting and resistance to dissolution of metallization for 30 s at
In wave soldering, the dissolution rate of metallization significantly exceeds that of static dip methods Techniques such as wave, reflow, or vapor-phase soldering allow for additional iron soldering for repairs or touch-ups Consequently, a prolonged immersion at elevated temperatures is necessary to evaluate the metallization's resistance to dissolution in molten solder.
The severities of dewetting and resistance to dissolution of metallization shall depend on the components electrode structure
Application of the test methods to through hole reflow soldering components (THR) C.1 Solderability
The solderability of components designed for Through-Hole Reflow (THR) must be evaluated according to IEC 60068-2-20, Test Ta, method 1, with specific conditions outlined in Table C.1 that differ from the standard to simulate reflow soldering conditions The relevant specification should include a preheating requirement prior to immersion in the solder bath, typically involving positioning the test specimen 10 mm above the solder bath surface for 30 seconds.
Table C.1 – Test conditions for solderability test
Sn96, 5Ag3Cu , 5 235 °C, (5 ± 0, 5) s recommend ed
Test Td 2 , method 2, reflow simulation without solder shall be used The test conditions related to the respective soldering process group apply
Test Td 3 , method 2, reflow simulation without solder shall be used The test conditions related to the respective soldering process group apply
The criteria for evaluation shall be provided by the component specification
Annex X (informative) Cross reference for references to the prior revision of this specification
The updated sectional specification features a revised structure, and the table below offers a cross-reference for all elements mentioned in the previous version of this specification.
Cl ause/Su bclau se
5 — The prescri pti ons on precondi ti oni ng are all ocated wi th the separate tests Td 1 , Td 2 , or Td 3 , see bel ow
I f appli ed to test Td 1
I f appli ed to test Td 2
I f appli ed to test Td 3
6 — Th e prescri pti on s on the sold er bath method are all ocated wi th the separate tests Td 1 , Td 2 , or Td 3 , see bel ow
I f appli ed to test Td 1
I f appli ed to test Td 2
I f appli ed to test Td 3
I f appli ed to test Td 1
I f appli ed to test Td 2
I f appli ed to test Td 3
I f appli ed to test Td 1
I f appli ed to test Td 2
I f appli ed to test Td 3
Th e prescri pti on s on the sold er reflow method are all ocated wi th the separate tests Td 1 , Td 2 , or Td 3 , see bel ow
I f appli ed to test Td 1
I f appli ed to test Td 2
I f appli ed to test Td 3
I f appli ed to test Td 1
I f appli ed to test Td 2
I f appli ed to test Td 1
I f appli ed to test Td 2
Cl ause/Su bclau se
The prescri pti on s concerni ng lead -free sol d er all oys are all ocated wi th the separate tests Td 1 , Td 2 , or Td 3 , see bel ow
I f appli ed to test Td 1
I f appli ed to test Td 2
Th e prescri pti on s concerni ng lead con tai ni ng sol d er all oys are all ocated wi th th e separate tests Td 1 , Td 2 , or
I f appli ed to test Td 2
I f appli ed to test Td 3
I f appli ed to test Td 1
I f appli ed to test Td 2
Annex C — I nformation relevant to compon ents for th rough-h ole refl ow sol deri ng is avail abl e in I EC 61 760-3
Bi bli og raphy Bi bli ograph y —
I EC 60068-2-54, Environmental testing – Part 2-54: Tests – Test Ta: Solderability testing of electronic components by the wetting balance method
I EC 60068-2-69, Environmental testing – Part 2-69: Tests – Test Te: Solderability testing of electronic components for surface mounting devices (SMD) by the wetting balance method
IEC TR 60068-3-1 2, Environmental testing – Part 3-12: Supporting documentation and guidance – Method to evaluate a possible lead-free solder reflow temperature profile
I EC 60068-3-1 3, Environmental testing – Part 3-13: Guidance on Test T: Soldering 3
I EC 60749-20, Semiconductor devices – Mechanical and climatic test methods – Part 20: Resistance of plastic-encapsulated SMDs to the combined effect of moisture and soldering heat
I EC 61 760-3, Surface mounting technology – Part 3: Standard method for the specification of components for through hole reflow (THR) soldering
I EC 61 760-4, Surface mounting technology – Part 4: Standard method for classification, packaging, labelling and handling of moisture sensitive devices 4
J-STD 020D, Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices http: //www.jedec.org/sites/default/files/docs/jstd020d-01 pdf
J-STD 075, Classification of Non-IC Electronic Components for Assembly Processes
4 Ensemble des procédés de brasage et sévérités d'essai associées 45
5 Matériel d'essai 46 5.1 Bain de brasage 46 5.2 Équipement de refusion 47
6 Essai Td1 : Brasabilité des bornes 47 6.1 Objet et description générale de l'essai 47 6.2 Préparation des éprouvettes 47 6.3 Vieillissement accéléré 47 6.4 Mesurages initiaux 47 6.5 Méthode 1 : Bain de brasage 48
6.5.3 6.6 Méthode 2: Brasage par fusion 50 Équipement de refusion 50
Profil de température de brasage par fusion pour l'essai Td1 51
7 Essai Td2: Résistance à la chaleur de brasage 53 7.1 Objet et description générale de l'essai 53 7.2 Préparation des éprouvettes 53 7.3 Préconditionnement 53 7.4 Mesurages initiaux 54 7.5 Méthode 1 : Bain de brasage 54
7.5.3 7.6 Méthode 2: Brasage par fusion 56 Équipement de refusion 56
8 Essai Td3: Démouillage et résistance de la métallisation à la dissolution 59 8.1 Objet et description générale de l'essai 59 8.2 Préparation des éprouvettes 59 8.3 Mesurages initiaux 59 8.4 Méthode 1 : Bain de brasage 59
8.5 Méthode 2: Brasage par fusion 60 Équipement de refusion 60
Application du profil de refusion 61
9 Mesurages finaux 61 9.1 Retrait du flux 61 9.2 Conditions de reprise 61 9.3 Évaluation 61
Résistance à la chaleur de brasage 63
Résistance de la métallisation à la dissolution 63
1 0 Renseignements à indiquer dans la spécification applicable 63