Cheap parts for soldering practice.  - Page 1
Forum section: electronics / beginners

author: WatchfulEye
author_rank: Regular Contributor
timestamp: June 10, 2022, 01:47:30 pm
content: I'm looking to try and practice soldering some QFN and maybe some coarse BGA parts to test crude reflow capabilities.Just looking for some ideas of cheap, readily available parts which could be easily integrated into a simple circuit to confirm functional solder joints.I had originally though some 74 logic, but I'm already happy with TSSOP and am not interested in the X2SON and similar packages.MCUs are a possibility but I've only set up tooling for microchip arm which are largely non-existent at present.

author: MikeK
author_rank: Super Contributor
timestamp: June 10, 2022, 03:49:17 pm
content: eBay has SMD soldering practice kits. Not sure if they have QFN and BGA, though.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 10, 2022, 04:14:00 pm
content: For both QFN's and BGA's you need the package and a matching PCB.You could start by practicing on any scavenged electronics you can find. Put some kapton tape and aluminimum foil around a part, desolder it with hot air, clean it, apply new flux and solder and solder it back. If it still does something after you've done this, you probably did it right.

author: wraper
author_rank: Unknown
timestamp: June 10, 2022, 04:30:03 pm
content: If you want cheap practice parts, go to some distributor, for example LCSC (since it sells cheap Chinese branded parts), select type of part you need, in parametric filter select package type you need. Sort them by lowest price and buy the cheapest. Empty packages in soldering practice kits are almost always more expensive than cheap real components. As of PCB, likely it will be cheaper to order a custom PCB with a bunch of footprints thrown in from a cheap PCB house.

author: WatchfulEye
author_rank: Regular Contributor
timestamp: June 10, 2022, 08:21:02 pm
content: Quote from: wraper on June 10, 2022, 04:30:03 pmGood tip. Thanks.Looks like LM324 and 74 series buffers are suitably cheap and supply is excellent in QFN. Not the most exciting parts, but they'll be easy to test function and connectivity. The BGAs I'm less fussed about, and supply of these is not as good, most of the bargain basement BGAs are chip-scale 0.35 mm or similar, so basically pointless. The best I could find was some serial flash memories with 1 mm ball pitch, which I could potentially find a use for, but they're about 10x the price of an LM324, so not worth it for practice use.This is also a good opportunity to get more familiar with kicad, designing footprints and practicing the overall custom PCB workflow.

author: CaptDon
author_rank: Super Contributor
timestamp: June 11, 2022, 12:32:33 am
content: I went to school for the Fuji chip shooter SMD machines in Vernon Hills Illinois. They had tons of 'dummy' I.C.'s in all kinds of packages for the students to 'pick-n-place' on practice boards. The parts were unmarked and it was assumed they were 'duds' that failed QC/QA somewhere. Apparently no one at Fuji ever tried to use or test one of these 'unknowns' to see if they had any guts inside or where just dummies. Interesting question however by the O.P.!! Some of the machines approached 20,000 pounds and it was interesting to see one guy move the machines with an 'Air Float' on a mirror smooth concrete floor!!!

author: james_s
author_rank: Super Contributor
timestamp: June 11, 2022, 01:10:10 am
content: I would suggest going a step further when designing a practice PCB and try to build some kind of trivial circuit that actually makes use of at least some of the parts. Even if it's just a blinky LED or something it makes it a tad more interesting and allows you to confirm that your soldering works. As someone else suggested just browsing distributors for the cheapest part in the packages you want is a valid approach, you can also look on ebay and see what turns up, or give rework a try, stuff like old broadband routers frequently turn up for peanuts at thrift shops and that's a fairly complex working device you can try swapping the RAM, ROM, CPU, etc, reinstall and see if it still works. If it doesn't you can keep using the board for practice.

author: taste_tester
author_rank: Regular Contributor
timestamp: June 11, 2022, 08:51:32 am
content: For BGA practice try a cheap toaster oven!!the ones that can do air frying as well tend to have quite accurate temperature too...

author: WatchfulEye
author_rank: Regular Contributor
timestamp: June 11, 2022, 11:03:12 am
content: Thanks all.I'm going to make this a bit more of a holistic project, so I'll have a go with schematic and PCB design, and build something simple.As it was I was browsing LCSC and secured a bunch of quad comparators for about 20c per package, as well as some 8 channel 74 line drivers at 9c per package, as well as a life time's supply of 0805 LEDs, so a bar graph volt meter is an obvious project.LCSC were also having a clearance on quad NAND gates at 0.3 c per package, so I bought a life time's supply of those.I like the idea of finding some old routers and practicing desoldering and resoldering. I'll certainly think about that.

author: agehall
author_rank: Frequent Contributor
timestamp: June 12, 2022, 02:58:37 pm
content: The big problem with practicing BGA soldering is knowing if you got it right or not. It is pretty hard to verify that the soldering is OK unless you build a working PCB out of it.I bought som cheap ATTiny (or similar - don’t remember right now) in BGA packages before the chip armageddon started and have always planned to make a custom PCB that allows me to build a simple board where I can test the MCU after it is soldered. Never got around to the last part but lately I’ve been thinking about finishing this project.

author: Shock
author_rank: Super Contributor
timestamp: June 13, 2022, 04:13:22 am
content: Practice on some ewaste is the cheapest and most realistic way.

author: tepalia02
author_rank: Regular Contributor
timestamp: June 13, 2022, 10:41:09 am
content: What's your budget by the way?