National Semiconductor Application Note 2029 Martin Schnepf June 18, 2010 Introduction inside the package can create excessive internal pressure resulting in delamination or even cracked package (popcorn effect). NSC’s components that are considered moisture sensitive are sealed in moisture barrier bags (MBB) together with a desiccant and a Humidity Indicator Card (HIC). National Semiconductor generally follows Industry Standards IPC/ JEDEC J-STD-020 and J-STD-033 to determine the moisture sensitivity level and corresponding floor life time for NSC’s plastic package types, for details on absolute maximum ratings for soldering see www.national.com/ms/MS/MSSOLDERING.pdf. The floor life time is the maximum time period from the opening of the MBB to the final reflow soldering process. The MSL Level and floor life time as per Table 1 is provided on NSC’s immediate and/or intermediate packing container label. Additionally, the MSL level and the maximum peak package temperature for National’s devices can be found within the Product Folder of National’s website. This Application Note provides recommendations for handling, storing and mounting of National Semiconductor’s surface mount IC packages. The final manufacturing yield and board level reliability are influenced by various factors and processes outside the control of the IC manufacturer. This Application Note can therefore only be used as a guideline and reference to support our customers. Due to the variety of possible board assembly materials and equipments, National Semiconductor Corporation (NSC) advises the user to consult the individual suppliers and vendors to achieve the optimum board assembly yield. Moisture Sensitivity Level Due to the hygroscopic nature of the plastic encapsulants, the plastic ICs absorb a certain amount of moisture. When subjecting a SMT device to reflow soldering process (e.g. infrared, convection, vapor phase), the entrapped moisture Handling & Process Recommendations Handling & Process Recommendations TABLE 1. Moisture Sensitivity Levels (According to IPC-JEDEC J-STD-033B.1 (Note 1) Floor Life (out of MBB) MSL Level Time ≤ 30ºC / 85% RH ≤ 30ºC / 60% RH 4 weeks ≤ 30ºC / 60% RH 168 hours ≤ 30ºC / 60% RH 72 hours ≤ 30ºC / 60% RH 48 hours ≤ 30ºC / 60% RH 24 hours ≤ 30ºC / 60% RH Mandatory bake before use. After bake, must be reflowed ≤ 30ºC / 60% RH 1 Unlimited (no moisture barrier bag) 2 1 year 2A 3 4 5 5a 6 Conditions within the time limit specified on the label Reflow Soldering Solderability tests were conducted on components after long term storage in warehouse conditions and after exposure to accelerated aging environment. Based upon the results, NSC’s shelf life of dry-packaged moisture sensitive devices inside the unopened moisture barrier bag is 3 years after original seal date when stored in an environment not exceeding 40ºC / 90% RH. Component storage outside the MBB should be done in a dry storage cabinet at < 25°C and < 10% R.H. to prevent any moisture absorption. The shelf life with regard to soldering of non dry-packed devices, i.e. MSL1, is 3 years provided the storage environment is controlled at ≤ 30ºC / 85% RH. Please be aware that e.g. bare die & wafer products have different storage conditions and limitations. The most popular soldering method for surface mount devices is forced convection reflow and therefore the topic of this chapter. Other possible solder processes for surface mount devices are, with restrictions, infrared reflow (IR), vapor phase and wave soldering. It is not possible for an IC manufacturer to provide a general reflow profile recommendation for the end customer in charge of the board assembly. Reflow furnace settings depend for example on the number of heating/cooling zones, type of solder paste/flux used, board and component size as well as component density. The actual temperature setting needs to be above the liquidus temperature (solder melting point) of the solder paste in order to form a reliable solder joint, while the upper limit is clearly defined by the maximum peak package body temperature depending on package thickness and volume as provided by IPC /JEDEC J-STD-020, see Table 2 and Table 3 Note 1: Copyright IPC/JEDEC. Reproduced with permission. © 2010 National Semiconductor Corporation 301141 www.national.com AN-2029 Storage and Shelf Life AN-2029 TABLE 2. Maximum Peak Package Body Temperature Tp (according to IPC-JEDEC J-STD-020D) For Pb-Free Process (Note 1) Package Thickness Volume < 350mm3 Volume 350-2000mm3 Volume > 2000mm3 <1.6 mm 260 °C 260 °C 260 °C 1.6 -2.5 mm 260 °C 250 °C 245 °C >2.5 mm 250 °C 245 °C 245 °C TABLE 3. For SnPb Eutectic Process (Note 1) Package Thickness Volume < 350mm3 ≥ 350mm3 <2.5 mm 235 °C 220 °C ≥2.5 mm 220 °C 220 °C It is important to understand that the temperature profile provided within IPC/JEDEC J-STD-020 reflects the profile used for device (MSL) classification see Figure 1 and Table 4 with the temperature measured on the top package surface during the reflow soldering process. The actual board assembly reflow furnace settings need to be developed separately depending on furnace characteristics and board design. The selected temperatures should not exceed the parameters used for MSL classification. Volume NOTE: Package volume excludes external terminals (e.g., balls, bumps, lands, leads) and/or nonintegral heat sinks. 30114101 FIGURE 1. Classification Reflow Profile (peak package body temperature) for Pb-free reflow soldering TABLE 4. Classification Reflow Profile Parameters (according to IPC-JEDEC J-STD-020D) (Note 1) Profile Parameter Pb-free Assembly SnPb Assembly Preheat Temperature range 150°C – 200°C 100°C – 150°C Duration 60-120sec 60-120sec Ramp-up rate Max 3°C/sec Max 3°C/sec Liquidus Temperature TL and 217°C 183°C Time above TL 60-150sec 60-150sec TP Peak Package Body Temperature See Table 2 See Table 3 Dwell time within 5°C of at TP Max 30sec Max 20sec Ramp-down rate Max 6°C/sec Max 6°C/sec www.national.com 2 If the Floor Life time is exceeded or the Humidity Indicator Card indicates excessive moisture after opening the MBB (the 30114102 FIGURE 2. Humidity Indicator Card as per IPC/JEDEC J-STD-033B.1 (Note 1) Conditions for drying components depend on package thickness, MSL Level and baking temperature. Table 5 provides an excerpt of IPC/JEDEC J-STD-033B.1 on drying mounted or unmounted SMD packages. Please note that standard packing material such as tape, reel and tubes cannot with- stand higher baking temperatures and the components need to be taken out of the immediate shipping container. Only high temperature trays are able to withstand baking process at 125 ºC. TABLE 5. Reference Conditions for Drying Mounted and Unmounted SMD Packages (as per IPC-JEDEC J-STD-033B.1) (Note 1) Bake @ 90°C ≤5% RH Bake @ 125°C Package Body Level Exceeding Floor Life by >72 h Exceeding Floor Life by Exceeding Floor Life by >72 h ≤72 h Exceeding Floor Life by ≤72 h Bake @ 40°C ≤5% RH Exceeding Floor Life by >72 h Exceeding Floor Life by ≤72 h Thickness 2 5 hours 3 hours 17 hours 11 hours 8 days 5 days ≤1.4 mm 2a 7 hours 5 hours 23 hours 13 hours 9 days 7 days 3 9 hours 7 hours 33 hours 23 hours 13 days 9 days 4 11 hours 7 hours 37 hours 23 hours 15 days 9 days 2 18 hours 15 hours 63 hours 2 days 25 days 20 days 2a 21 hours 16 hours 3 days 2 days 29 days 22 days 3 27 hours 17 hours 4 days 2 days 37 days 23 days 4 34 hours 20 hours 5 days 3 days 47 days 28 days 2 48 hours 48 hours 10 days 7 days 79 days 67 days 2a 48 hours 48 hours 10 days 7 days 79 days 67 days 3 48 hours 48 hours 10 days 8 days 79 days 67 days 4 48 hours 48 hours 10 days 10 days 79 days 67 days Thickness >1.4 mm ≤2.0 mm Thickness >2.0 mm ≤4.5 mm Note: For BGA package types >17x17mm, stacked die packages or packages with thickness > 4.5mm, please contact your local NSC sales representative 3 www.national.com AN-2029 color change is described on the HIC card, see Figure 2 ), baking is required prior to the reflow process in order to remove any moisture out of the plastic package. Drying of Components AN-2029 Repair Permissions In case repair or even replacement of a component is needed, it is important that the temperature used for repairing, desoldering or replacing the component, needs to be selected as low as possible to avoid any damage to the adjacent components or PC board. The repair profile should be similar to the actual reflow profile, common rework tools are either hot gun or available rework machines. In addition, depending on the MSL level of the component and if the floor life time from initial reflow soldering process to the repair process is exceeded, a baking process is required with parameters provided in IPC/JEDEC J-STD-033B.1. Otherwise, the accumulated moisture can cause damage as described in the previous chapters. Proper handling practices are required to prevent any ESD damages during any handling of the components. Note 1: Copyright IPC/JEDEC. Reproduced with permission. www.national.com 4 AN-2029 5 www.national.com Handling & Process Recommendations Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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