Gold cap IC - Page 1
Forum section: electronics / beginners

author: Nemo
author_rank: Newbie
timestamp: January 15, 2014, 12:37:36 am
content: I have always had this question, but couldn't really get a good answer searching about it on the Google.Does anyone know why these old/MIL-SPEC ICs came with gold-plated (I suppose it's plated, since it'd be ridiculously expensive to use pure gold) caps? I can somewhat understand the gold pins, but gold cap doesn't make any sense to me.Is there any specific reason to this? or is it solely for aesthetics?(Please refer to the attached image, for some reason the forum editor image function isn't working)

author: han
author_rank: Frequent Contributor
timestamp: January 15, 2014, 01:01:43 am
content: to prevent corrosion, that can affect chip wafer below..maybe....

author: Nemo
author_rank: Newbie
timestamp: January 15, 2014, 01:23:32 am
content: Quote from: han on January 15, 2014, 01:01:43 amI suppose oxidation could be a reason, but then why didn't they use zinc plating (galvanising) instead? or just aluminum. I think those would have been cheaper than heavily gold plating the cap.

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2014, 01:40:05 am
content: Quote from: Nemo on January 15, 2014, 12:37:36 amYep, lots of electronics is gold plated, it's only 1000 atoms thick or so.

author: han
author_rank: Frequent Contributor
timestamp: January 15, 2014, 05:01:24 am
content: I search the gold plating is for radiation protection (see Radiation hardening) and MIL-SPEC IC is not cheap, so gold plating is not increasing the price significantly, they use gold in bond wire afterall

author: deth502
author_rank: Frequent Contributor
timestamp: January 15, 2014, 06:06:23 am
content: Quote from: han on January 15, 2014, 05:01:24 ami would guess for some kind of shielding purposes myself.military contracts go to the lowest bidder, so i can guarantee you that its not there for looks.

author: free_electron
author_rank: Super Contributor
timestamp: January 15, 2014, 06:55:14 am
content: The gold flash is because of the sealing process used. You dont want too many metals in the mix.A silver particle paste is stenciled on the rim, the lid is placed on top of that and the part is sent through the oven. The silver solders the lid on the cavity. If done correctly this creates a hermetic sealThe cavity is gassed out during rampup and the actual soldering happens under pure nitrogen atmosphere.

author: amyk
author_rank: Super Contributor
timestamp: January 15, 2014, 07:31:28 am
content: Quote from: han on January 15, 2014, 05:01:24 amGold is not any good at radiation shielding.

author: BravoV
author_rank: Super Contributor
timestamp: January 15, 2014, 07:34:45 am
content: So the gold basically to ensure long term mechanical integrity of the metal lid from getting corroded thru time, since the chamber is pressurized ?

author: han
author_rank: Frequent Contributor
timestamp: January 15, 2014, 09:51:23 am
content: my bad...The gold only protect from UV and IR radiation...http://info.goldavenue.com/Info_site/in_glos/in_glos_foil.html

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 15, 2014, 04:11:27 pm
content: The base metal is Kovar or similar alloy chosen for a similar coefficient of thermal expansion as the ceramic package. The gold plating is to enhance conductivity, aid solderability, and protect the Kovar from corrosion.