DIN EN 62137-4:2015-07

This part of IEC 62137 specifies the test method for the solder joints of area array type packages mounted on the printed wiring board to evaluate solder joint durability against thermo-mechanical stress. This standard applies to the surface mounting semiconductor devices with area array type packages (FBGA, BGA, FLGA and LGA) including peripheral termination type packages (SON and QFN) that are intended to be used in industrial and consumer electrical or electronic equipment. The test method described in this standard is not intended to evaluate the semiconductor devices themselves. For the application of this document, the terms and definitions according to IEC 60191-6-2, IEC 60191-6-5 and IEC 60194 and the terms introduced shall apply. The purpose of the test procedure described in this standard is to assess the resistance to thermal stress of soldered joints on a package mounted on a substrate, but not to test the mechanical strength of the package itself. The test method described in this standard is mainly applicable to solder joints between the substrate materials of printed circuit boards and the package as the object of evaluation. The Test Device and Materials chapter covers the test specimen, reflow soldering equipment, temperature change chamber, short interruption detector, test substrate, and solder paste. Solder paste is manufactured from flux, finely divided solder particles and additives to promote wetting and control viscosity, adhesion, slippage, drying rate, etcetera. Unless otherwise stated in the product specification, one of the listed solder alloys (as described in IEC 61190-1-3) shall be used. The product specification should contain the details of the solder paste. When preparing the test specimen, the package must be mounted on the substrate using the following reflow soldering procedure. The package used as test specimen shall be modified as test package in such a way that after reflow soldering a circuit is formed with the connection surface pattern of the test substrate. The temperature change test is performed according to Test Na (fast temperature change with prescribed transition time), described in IEC 60068-2-14, with the following details. The test specimen shall be placed in the temperature change chamber where the best air flow prevails and where sufficient air flow surrounds the test specimen. The test shall be carried out in accordance with the cycles specified in the product specification. The electrical resistance of the circuit shall be continuously monitored during the test using the short-time interruption detector described. If the electrical resistance of the circuit increases due to the break of the solder joint, then the number of test cycles at this point represents the test specimen failure rate. The lifetime at thermal cycling should be statistically determined as the mean lifetime or characteristic lifetime of the Weibull distribution from the failure cycle data of the test specimen. The informative Annex A deals with the acceleration of the thermal cycling test for solder joints, describing the acceleration characteristics for evaluating the durability in the field from the results of thermal cycling tests of solder joints. The informative Annex B deals with current continuity testing for soldered joints of enclosures. This Annex refers to the test to evaluate the durability of the soldered joint of the enclosure using the current passage. The informative Annex C deals with the reflow solderability test procedure for packages and test substrate pads, giving an explanation of the test procedure for the reflow solderability of packages. The informative Annex D contains the design guideline for the test substrate. An explanation of the design guideline for the test substrate is given in the Annex. It applies to the PCB design guideline to be used to assess the durability of packages. For substrates, both the thickness and configuration of the layers and the mounting density on the substrate have a significant impact on the lifetime of the solder joint with the package mounted on the substrate under temperature cycling stress. It is known that the durability of the soldered joint is halved if, in particular, the surface matrix packages are mounted on the same area on both sides of the substrate. If the packages under evaluation may be mounted on a double printed circuit board, then evaluation of the lifetime of the solder joint with the components mounted on both sides of the substrate is recommended. The informative Annex E explains the heat resistance of the test substrate to reflow soldering. An explanation of the heat resistance of the test substrate to reflow soldering is given. If the test substrate does not have sufficient thermal stability, then the test substrate may deform during the reflow soldering process so that the durability of the solder joint basically cannot be evaluated by the thermal cycling test. The informative Annex F contains tensile strength measurement methods for the test substrate terminal pad. An explanation of the tensile strength measurement method for the substrate terminal pad is given here. If the test substrate has a poor terminal pad tensile strength, then the durability of the solder joint basically cannot be evaluated in the thermal cycling test. The following parameters have a lasting effect on the result. The tensile speed, the temperature at which the tensile strength test probe is mounted (method of fixing the probe using heat), the temperature of the probe during the tensile strength test (method of fixing the probe using heat). The informative Annex G contains standard mounting procedures for the enclosures. An explanation of the standard mounting procedure for the enclosures is given in the Annex. The informative Annex H describes the mechanical stresses of the enclosures. The Annex gives an explanation of the mechanical stress after mounting the packages on the printed circuit board. If the mounted package is subjected to mechanical stress, then the thermal cycling test can basically have a variety of effects on the durability of the soldered joint. The responsible committee is DKE/K 682 "Montageverfahren für elektronische Baugruppen" ("Electronics assembly technology") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.