LQFP 100 soldering - Page 1
Forum section: electronics / general

author: garfunx
author_rank: Newbie
timestamp: May 05, 2013, 03:40:55 pm
content: Hi,For a previous project, I succeed in soldering 64 TQFP package on multiple boards with a flux pen. But now I'd like to solder 100 LQFP package. Before to start designing and buying components, I'd like to know if someone already try to perform a such operation.Thank you!

author: Harvs
author_rank: Super Contributor
timestamp: May 05, 2013, 11:24:17 pm
content: It's no different to soldering a 64pin. Hand soldering all the way up to 208pin QFPs isn't challenging, you just use the same techniques.

author: c4757p
author_rank: Super Contributor
timestamp: May 05, 2013, 11:27:35 pm
content: Yep. Piece of cake unless you're a massive hamfist. Use flux, flux, and more flux, and when you think you have enough flux, add flux.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 05, 2013, 11:34:14 pm
content: Do you just use a flux pen? Or some other delivery method.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 06, 2013, 12:05:56 am
content: Flux pen, refilled from a bottle of liquid flux as pens are an expensive way of buying flux.Also remember flux only works once - once it's seen a soldering iron, clean off and re-flux.

author: Psi
author_rank: Super Contributor
timestamp: May 06, 2013, 12:15:29 am
content: Also get some good quality solderwick (Chemtronics) to remove excess solder or bridges.Be careful if you have IC pads not connected to anything, they will lift/rotate pretty easily, especially if you have the iron too hot

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 06, 2013, 01:48:58 am
content: No worries about the "soder" wickQuoteI guess you mean the pcb pads not connected, and not the ic legs. I do have quite a few NC pads. So on these the IC legs will solder to the pad but not be connected to anything else. I will be reasonably careful.I only have the no clean flux pen at the moment I will get a rosin flux pen and a bottle of liquid flux. No sure how the refill works I guess it will become obvious once I need to do it.According to my gerbers I have managed to put 0.17mm of mask between each 0.5mm pitch pin, obviously there isn't much space between the edge of the mask and the side of the pins.I have been told it is better not to use mask at all for this pin pitch. (Seeed Studio design tolerances). Any thoughts on this? I was intending to reflow solder and then drag solder only if I had any shorts.Also I chose enig rather that hasl. Worth doing if hand soldering?I only need to do a dozen boards.Hopefully I am remaining on topic with these questions.

author: c4757p
author_rank: Super Contributor
timestamp: May 06, 2013, 01:54:09 am
content: Quote from: HackedFridgeMagnet on May 06, 2013, 01:48:58 amNot a big deal if you're hand soldering, but...QuoteSlightly more important with reflow. I'd consider completely drag-soldering this one.QuoteNot at all.QuoteSo... how's the weather where you live?

author: Psi
author_rank: Super Contributor
timestamp: May 06, 2013, 02:17:57 am
content: Quote from: HackedFridgeMagnet on May 06, 2013, 01:48:58 amSorry yeah, i mean the pcb pads.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 06, 2013, 03:27:56 am
content: QuoteFrom what I remember the advantage of no solder mask was that the chip had more chance of sitting flat if something was misaligned.Anyway I will soon find out.I did some some small DFNs 0.45mm pitch once with a thermal pad and no solder mask, they were quite troublesome, I guess that is the only reason I am a bit worried, these should be heaps easier.Weathers perfect. Here's a picture.

author: c4757p
author_rank: Super Contributor
timestamp: May 06, 2013, 03:57:16 am
content: Wow! The general atmosphere in that picture looks surprisingly similar to where I live (southern New York State, way inland from NYC) in autumn. If I suddenly woke up there it'd take me a while to realize I wasn't at home... I suppose itisautumn in Australia, but just the general look of the plants, terrain, etc. At risk ofcompletelyderailing the discussion, whereabouts in Australia do you live?In the interest of proving I'm notonlyhere to talk about climate - yep, I've found DFN/QFN troublesome without solder mask. You really have to reflow them, usepreciselythe correct amount of solder paste, and they seem pretty finicky about temperature profile as well.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 06, 2013, 05:34:40 am
content: Yes I think the amount of solder paste was the problem, that and having pads that can short underneath the chip.Back to derailing this thread, I thought the Eucalyptus would make it look quite different from the US but there are pines in the picture too. And obviously because most of our trees are evergreens we dont get much in the way of Autumn colours.ps. The weather isn't always as nice as today. 43 degrees 3' south on the East coast, the water is named North West Bay. Funny considering we are South East of just about everything.

author: poorchava
author_rank: Super Contributor
timestamp: May 06, 2013, 06:59:52 am
content: Difficulty in soldering QFPs comes from fine pitch rather than number of pins. Anything down to 0.6mm is trivial. 0.5mm is too, but requires careful inspection for accidental shorts (use lots of flux).

author: BravoV
author_rank: Super Contributor
timestamp: May 06, 2013, 07:06:48 am
content: Mind share what is your favorite solder tip in drag soldering these tiny pitch xQFP pins ?

author: peter.mitchell
author_rank: Super Contributor
timestamp: May 06, 2013, 08:27:41 am
content: When reflowing these, i like to have the pads a bit longer than normal, so the excess solder will pull onto the pad better and be less likely to bridge.

author: Psi
author_rank: Super Contributor
timestamp: May 06, 2013, 11:24:11 am
content: Quote from: peter.mitchell on May 06, 2013, 08:27:41 amYeah, i forgot to do that in a recent project and it definitely bridges more often than normal.

author: poorchava
author_rank: Super Contributor
timestamp: May 06, 2013, 01:39:59 pm
content: Quote from: BravoV on May 06, 2013, 07:06:48 amI use 'knife-blade' tip. Specifically this one (website for reference only, I bought it elsewhere:http://www.vetco.net/catalog/product_info.php?manufacturers_id=13&products_id=12651I actually use that tip for pretty much everything.