MC33078: About MSL of MC33078.

Hi Kazuya-san,

Q1. J-STD-033 has been updated and the latest version is 033D.

You are correct. IPC/JEDEC J-STD-033D supersedes the revisions shown below, as the document indicated. IPC/JEDEC J-STD-033D document is the latest recommendation from JEDEC Committee (JEDEC JC-14.1 Committee).  

If the sealed humidity indicator card did not change color, then the moisture contents or level within the package have been unchanged due to the storage, and baking steps are not required. 

Q2. About "9.Manual Repair Procedure" on page 10 of AN-2029:

Ok, AN-2029 application note spelled out the maximum tip temperature and duration for repair work. Personally, I never had to micro-manage solder iron tip temperature. If the soldering surface is large with heavier gauge wires, I tend to use larger and higher soldering temperature tip (e.g. SMD inductors and transformers etc.). If parts are small (e.g. op amp, transistor, resistors etc), I tend to use small soldering tip size and lower temperature soldering tip. If a selected solder iron tip takes a longer time to melt a solder, I tend to change the tip size/temperature of the tips (I use Metcal soldering iron in general). 

Generally, a solder alloy should melt immediately when soldering tip is in contact with the solder, and the contacting time should be as short as possible. I tend to cover the soldering area with generous amount of flux, where flux should cover the tip of iron and soldering area. This is to prevent the additional solder alloy surface oxidation at the iron's contact point. Flux can shield oxygen away from the soldering surface. Oxidized metal surfaces tend to have higher melting point, poor heat transfer and may create brittle bonding or cold soldering joints in manual IC repair work.

In Metcal soldering system, the tip temperature is basically fixed. The size of the tip will determine the amount of energy at soldering tip. When the tip is in contact with another surface/metals, the soldering tip energy will be transferred to the contacted area. The nominal eutectic melting point are 220-240C for Sn/Ag based solders (Pb free). At the thermal contact instant, the iron tip temperature should be still above the Pb free melting points. If one has to wait (say >1 sec) for the iron to heat-up because of loss of thermal energy at the contact instant, the iron tip's energy may not be adequate  (tip size - contact tip surface + tip temperature + heating rate for non-Metcal soldering system). 

Enclosed is the max. tip temperature from Metcal solder station models for your references. 

/cfs-file/__key/communityserver-discussions-components-files/6/Metcal_2D00_Maximum_2D00_Tip_2D00_Temperature.pdf

If you have additional questions, please let us know.

Best,

Raymond