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Package Reflow Profiles

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Abstract

Reflow profiles are dependent on numerous factors including package type, number of components, board layers, board size, reflow oven accuracy and process and more.

Because of the number of variables it is not possible to provide a single reflow profile that is representative of every board using a specific package type. Typically manufacturing houses have reflow profiles in place and modify them for specific hardware.

The reflow profiles in this application note are provided as a reference to assist customers and manufacturing houses in customizing the reflow profile to specific hardware for the package type indicated. Therefore the information provided is not considered a final reflow profile.


Optimized Reflow Profiles

For optimal reflow results in achieving consistent solder joint geometries the reflow profile should be developed in cooperation with the solder paste supplier and with the equipment supplier as needed. The solder paste vendor's datasheet includes recommendation for reflow profiles based on alloy melting temperatures and flux activity. These recommendations must be followed to achieve optimal flux activity resulting in wetting of the lead surface. The flux activity in the solder paste plays an important role in facilitating solder wetting resulting in consistent solder joint geometries.

In the event SnPb or Sn lead finish are compared to NiPdAu solder joint geometries, be aware there are distinct but acceptable different solder joint geometries for NiPdAu lead finish. Refer to Evaluation of Nickel/Palladium/Gold-Finished Surface-Mount Integrated Circuits application note and Factors That Influence Side-Wetting Performance on IC Terminals application note for more information.


Maximum Reflow Temperature

The maximum allowed reflow temperature is stated on the Moisture Sensitivity Label (MSL). The following provides a detailed MSL explanation.

The maximum allowed reflow solder temperature is specified for Pb-free and non Pb-free soldering per the international Standard JEDEC 020D.1. The standard may be downloaded from the JEDEC web page


https://www.jedec.org/document_search?search_api_views_fulltext=JSTD020


This standard describes the Temperature versus Time maximum for a reflow profile used in Pb-free and non Pb-free soldering. These conditions are used also for the package qualification tests and are intended to be referenced as the allowable reflow profile ranges for device level qualification testing and not a recommendation for solderability.

Older packages may have used earlier versions of the JEDEC 020 standard which are grandfathered (considered acceptable). The allowed maximum reflow peak temperature is listed on the device MSL label on the tape and reel. Sometimes multiple values may be given indicating different humidity exposure levels and with associated processing temperature.


Reference Reflow Profiles

The following reflow profiles are provided as reference when working with a manufacturing house to generate a final reflow profile specific to the hardware using the specified package type. This information is provided for reference only and should not be used as the final reflow profile. Final reflow profiles must be worked out between the customer and manufacturing house.


Table 1. Reference Reflow Profiles for CBB and CBC Package Types


Pre-Heat Temperature (oC)
Pre-Heat Dwell Time (sec)
Time above Liquid (sec)
Peak Reflow Temperature (oC)
Duration at Peak Reflow Temperature (sec)
Cool Down Rate (deg C/sec)
Conveyor Speed (cm/min)
CBB (12x12mm, 0.4mm, top - 0.5mm)/ CBP (12x12mm, 0.4mm, top - 0.5mm)
CBP (12x12mm, 0.4mm, top - 0.5mm)/ CBP (12x12mm, 0.4mm, top - 0.5mm)
165-185
60-120
30-60
250
10
8
50
CBC(14x14mm, 0.5mm, top – 0.65mm)
60-120
10
30-60
250
20
8
What ever is required to accomplish desired reflow profile
CUS(16x16mm, 0.65mm)
150 +/-10
90 +/-30
30-60
245-250
10
8
What ever is required to accomplish desired reflow profile



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