Soldering BGA when used to use leaded solder... - Page 1
Forum section: electronics / general

author: cgroen
author_rank: Unknown
timestamp: April 20, 2017, 08:02:18 am
content: I have been doing a lot of "conventional stuff" with QFP, LCC etc. I have always wanted to get into handling BGA's for prototyping and have now my first testboard with BGA's on it (CPU + SDRAM), this is just a board with no real use, just to check BGA mounting etc.I have preheat equipment, hotair etc. I have always used leaded solder for prototyping as this was much easier. But, when I get my hands on the BGA stuff they already comes with balls (obviously) which are lead free! I guess I have a fear for the higher temperatures/handling of the non leaded stuff, but do I have to be afraid or is this really just "business as usual" although with a little higher temperatures ... ?The packages are 180 and 54 pins with 0.8 mm spacing

author: cgroen
author_rank: Unknown
timestamp: April 20, 2017, 12:06:58 pm
content: Also, do any of you solder lead free BGAs using leaded paste ? When searching it seems that some say its "ok" and some say "dont do this"...Any real world experience from fellow engineers ?

author: TJ232
author_rank: Frequent Contributor
timestamp: April 20, 2017, 07:45:35 pm
content: It is recommened to not mix leaded with lead free for a lot of reasons, some technical (bad solder joints, BGA balls nightmare, flux incompatibility, etc) and some legal (might end up with RoHS violation).

author: Lawsen
author_rank: Frequent Contributor
timestamp: April 21, 2017, 02:42:44 am
content: One should not mixed solder between lead and silver because of different metals could cause galvanic corrosion by electricity flowing between the difference metals. If you are required to use lead free during a production circuit then you have no choice but use lead free. If you are prototyping or just for yourself then lead is allowed but sometime in the future the prototype might get thrown away that is when the lead will be a problem to drinking water. I have a pound of lead solder that I need to use up before switching to silver solder. Circuits that I sell are lead free but circuits for myself are lead because I am trying to used up my 1 pound lead solder that I inherited.

author: cgroen
author_rank: Unknown
timestamp: April 21, 2017, 07:27:57 am
content: Thanks for the input guys!I might just go ahead and mount the two BGAs with no-lead solder, and then the rest of the circuit as I normally do with prototypes. The board will stay in my lab, it is only a "first try" at BGA on the bench, nothing else. In the company, we design all our stuff with BGAs and various lead less packages but layout (and production) is done by sub-contractors.

author: TJ232
author_rank: Frequent Contributor
timestamp: April 21, 2017, 02:29:45 pm
content: Quote from: cgroen on April 21, 2017, 07:27:57 amI would suggest you to give a try to the GC10. Worth any extra money you might need to pay. Just pay attention to order the right particle size ones: T3 or T4, depending on your needs.

author: cgroen
author_rank: Unknown
timestamp: April 21, 2017, 02:34:09 pm
content: Quote from: TJ232 on April 21, 2017, 02:29:45 pmI do in fact already have GC10 (in T4), expiry data was unfortunately october last year, but it has been keep in the cooler (3 deg C) since I bought it so hope it is still usable ?It is untouched as I never took the "lead-less" routeBoard will arrive in 3 to 4 weeks time (OSHPark) I also ordered a stainless steel stencil from OSHStencils

author: TJ232
author_rank: Frequent Contributor
timestamp: April 21, 2017, 05:17:43 pm
content: Quote from: cgroen on April 21, 2017, 02:34:09 pmGC10 doesn't need to stay in the freezer at all. But as it happened already, before usage just take it out from there, let it stay in the room temp for about 12 hours and after that you can unseal the container, give it a good mix, and you might be good to go.

author: John_ITIC
author_rank: Frequent Contributor
timestamp: April 22, 2017, 08:28:14 pm
content: Just use leaded solder for everything. You will have no issues what so ever. But make sure to use higher reflow temperatures so that the leaded BGA balls melt properly.

author: TJ232
author_rank: Frequent Contributor
timestamp: April 22, 2017, 08:41:44 pm
content: Quote from: John_ITIC on April 22, 2017, 08:28:14 pmBelieve it or not, these days most of the BGA stuff comes with lead free balls. And the number of available leaded versions is going soon near zero. Or pay the price for special mil/whatever specs. I know a company doing reballing to leaded, but they have a very, very good reason behind.

author: John_ITIC
author_rank: Frequent Contributor
timestamp: April 23, 2017, 02:30:03 am
content: Quote from: TJ232 on April 22, 2017, 08:41:44 pmYes, I meant lead-free BGA balls. The point is that it is fine to mix leaded/non-leaded for prototype work.

author: cgroen
author_rank: Unknown
timestamp: May 10, 2017, 04:40:30 am
content: Success!Yesterday I received the PCB boards from OSHPark and tried to do some assemblyThe first board was not so lucky, I think I had put too much pressure on the SDRAM device, I could see that the solder balls has been "flattended" to the point where they touched their neighboring "balls"The second board was a total success!I started out by finding the best spot for the IR heater, for the process I used around 140 to 150 deg C (top PCB temperature). I know it is not the best approach to place the PCB right on top of the IR heater, but I was in a hurryIt's fun actually to see how much you can "wiggle" a BGA device when it reflows, you give it a tiny push with a pair of tweezers and it immediately jumps back.I have attached a number of pictures in random order...

author: TJ232
author_rank: Frequent Contributor
timestamp: May 10, 2017, 04:55:02 pm
content: Somebody had a lot of fun out thereNow next step, play the fancy game also with some lead free stuff, yeah, your GC10 jar is waiting you!

author: cgroen
author_rank: Unknown
timestamp: May 10, 2017, 05:27:23 pm
content: Quote from: TJ232 on May 10, 2017, 04:55:02 pmIt was interesting and in fact easier than I thought! I will try and mount the last of the 3 PCBs using the GC10 in a couple of days, maybe I'm lucky once againThanks to all for input