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Electronics => Beginners => Topic started by: radiolistener on March 01, 2024, 10:47:34 am

Title: What is proper soldering process for LFCSP-64 package?
Post by: radiolistener on March 01, 2024, 10:47:34 am

I bought radioberry (https://github.com/pa3gsb/Radioberry-2.x) board on aliexpress, but the seller sent me broken device, it don't works. According to tests, unfortunately the root of cause is dead AD9866 (https://www.analog.com/media/en/technical-documentation/data-sheets/AD9866.pdf) chip. It has clock on the input, but no clock on the output (both pin 19 and pin 61 are always zero) and there is no sign of life on its outputs. :(

I'm thinking to try to repair it by replacing AD9866 (https://www.analog.com/media/en/technical-documentation/data-sheets/AD9866.pdf) chip. But it looks not so easy. I never soldered such chips with a thermal pad on the bottom and don't know how to solder it properly. Could you please help?

Does thermal pad should be soldered together with usual pins with heating, or it should be soldered later by putting some solder into through hole in PCB?

What is the best way to desolder it and avoid damage and unsolder for other components?

Title: Re: What is proper soldering process for LFCSP-64 package?
Post by: JustMeHere on March 02, 2024, 02:33:18 am

Hot air.  Possibly a pre heater.   Very steady hands.  Possibly some chip quick.  Google some videos

Title: Re: What is proper soldering process for LFCSP-64 package?
Post by: Jwillis on March 02, 2024, 03:11:33 am

Found this Application Note (https://c44f5d406df450f4a66b-1b94a87d576253d9446df0a9ca62e142.ssl.cf2.rackcdn.com/2018/08/AN3015B-Amkor-DRMLF-App-Note-0818.pdf)
Page 9 has some guidelines for rework.
The data sheet for the AD9866 has a link to a application note on page 44 PCB DESIGN CONSIDERATIONS. But doesn't work. But I did find this https://amkor.com/document-library/?looking_for=lfcsp-64 (https://amkor.com/document-library/?looking_for=lfcsp-64) which might have more information.

Title: Re: What is proper soldering process for LFCSP-64 package?
Post by: Solder_Junkie on March 02, 2024, 09:11:06 am

Do not use Chip Quik, not only won’t it help, it leaves a horrid alloy on the board that is hard to remove. I have used it on SMD boards but regretted it afterwards.

Those ICs with underside heat transfer pads can be removed with hot air alone. The problem then becomes one of placing a replacement with high accuracy (and keeping it there) while you re-heat the board.

Return the faulty board and buy from a reputable source. Or put it down to experience and throw it in the bin.

SJ