STMicroelectronics devices are requalified to ensure their resistance to new soldering temperatures requested by PC board mounting with Tin-Silver-Copper alloys : melting temperature of 217°C instead of 183°C for SnPb eutectic alloy.
STMicroelectronics, together with Philips Semiconductors and Infineon Technologies (E3) have published and used a hotter profile with Peak Body Temperature at 260°C for small body packages, in anticipation of new JEDEC standard J-STD020C and to follow the demand from several customers .
ECOPACK™ components ensure no reliability risk due to whiskers growth see Application notes AN2035 .
ST Corporate Policy is to qualify each package family through test vehicles representative of the most critical parameters .
A typical qualification procedure includes:
Manufacturing processes assessment in assembly plants, Specific process validation, e.g. Tin plating process whiskers growth assessment, Qualification lots assembly for test vehicles defined by product divisions with assembly in–process quality controls, Package validation tests, including soldering ability with both SnPb and Pb-free SnAgCu solders, dimensional, visual and mechanical controls, Reliability tests.
BACKWARD & FORWARD COMPATIBILITY
Care has been taken to ensure that ECOPACK™ components are solderable using both current Lead and Lead-free PCB assembly processes. This ensures that our ECOPACK™ components can be integrated regardless of whether the assembly processes have already been converted to Lead-free or not.
However BGA type components will require a higher soldering temperature than Leaded equivalents.
The main difference between Pb and Pb-free soldering process is the temperature range : Pb–soldering (215°C-240°C) vs Pb–free soldering (235°C-260°C).
a. Backward compatibility
NiPdAu and Sn products are compatible with a Pb containing soldering process (See Application Note AN 2034 about Soldering Compatibility). As a consequence, our customer assembly lines will not be af-fected by the use ECOPACK™ products and all stocks will be compatible with the various soldering processes. Therefore ST will implement its conversion schedule, as per the attached roadmap. For SnAgCu finishing (BGA) the compatibility is not fully guaranteed (soldering below 230° is critical).
b. Forward compatibility
Most of our packages are compatible with Lead-free soldering processes. Nevertheless when customers convert their production line to Pb-free before Pb-free products availability, due to the higher reflow temperature (235°C-260°C), a few devices containing Pb may not be qualified for such a temperature range (higher moisture sensitivity). It is the customer’s duty to make sure that our current Pb-devices are qualified with their new soldering process. It is important to note that the maximum temperature is mentioned on the Inner box label.
RELIABILITY: please see here
MOISTURE SENSITIVITY LEVEL (MSL)
All Pb-free Surface Mount Devices (SMD) have been re-qualified according to the JEDEC STD-020C compliant soldering profiles considering 3 classes of packages and 3 peak temperatures: 245°C, 250°C and 260°C.
The MSL is indicated on labels according to IPC/JEDEC Standard J-STD033.