Electronic – What does the e3 or e4 printed on an IC mean

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So after staring at a few ICs today, I was wondering what the "e3" or "e4" stands for on the top of an IC. For example, here is an e3:

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Best Answer

It is regarding the lead content or plating finish. Here is an excerpt from IPC/JEDEC J-STD-609:

e0 - contains intentionally added lead (Pb)

e1 - SnAgCu (shall not be included in category e2)

e2 - Sn alloys with no Bi or Zn excluding SnAgCu

e3 - Sn

e4 - Preplated (e.g., Ag, Au, NiPd, NiPdAu)

e5 - SnZn, SnZnx (no Bi)

e6 - contains Bi

e7 - low temperature solder (\$\le\$ 150C) containing Indium (no Bi)

e8, e9 - unassigned