Can I get away without gold plating for QFN packages? - Page 1
Forum section: electronics / projects

author: Starlord
author_rank: Frequent Contributor
timestamp: January 16, 2015, 02:31:18 pm
content: I noticed OSHspark has gold plating on all their boards. But Advanced Circuits doesn't on their $33 and $66 each promotions. And Gold Phoneix charges $100 extra for it.Is it absolutely necessary to use gold? I can't use silver because these are boards for hobbyists, so there will be through hole pads that aren't soldered, and silver tarnishes. And I'm pretty sure I can't use that organic coating on bare copper for the same reason.Gold Phoenix says on their site that they use high speed hot air to blow off excess solder when doing HASL to make it flatter. But will it be flat enough for 0.5mm pitch QFN packages with thermal pads on the bottom?I will be hand assembling the first few boards (hot plate, stainless steel stencil most likely), but I may have the PCB house manufacture the rest. So if gold is necessary for one or the other, I'll want to use it for both for consistency.Also, I'm only gonna get a hundred boards made. So if it's a matter of say 1% failing, and that being a big deal with large runs money wise, well, I'm not doing a large run, so I can accept if one or two boards out of a hundred don't work.Thoughts?

author: c4757p
author_rank: Super Contributor
timestamp: January 16, 2015, 02:31:45 pm
content: QuoteYes.

author: 8086
author_rank: Super Contributor
timestamp: January 16, 2015, 02:36:19 pm
content: You can get away with it, yes.I always get ENIG if I can though, it does make life a little bit easier.I would suggest maybe looking for a supplier that doesn't charge $100 extra for it. That seems excessive (for low quantity, if you're talking about 100+ boards then it's not so bad).

author: wraper
author_rank: Unknown
timestamp: January 16, 2015, 02:49:16 pm
content: Elecrow or Smart-protoryping? They charge around $15 for flash gold/ENIG IIRC. Lead free HASL produces much more flat surface compared to regular leaded HASL, not good if using leaded solder however.

author: wraper
author_rank: Unknown
timestamp: January 16, 2015, 02:53:34 pm
content: QuoteIt is not something special. It is standard part of any HASL process. HASL - hot air solder leveling.

author: Pjotr
author_rank: Frequent Contributor
timestamp: January 16, 2015, 05:15:33 pm
content: Have had no problems with standard HASL with QFN and thermal pads. ENIG is only useful for BGA's imho, but only when properly done. Have had gold plated boards without the nickel barrier (it seems) in the past. The gold was diffused away after a few months of storage and that boards became totally unsolderable.

author: rx8pilot
author_rank: Super Contributor
timestamp: January 16, 2015, 05:28:59 pm
content: I don't have any issues with QFN on PCBs without gold plating. Consider making the pads a little longer than normal for hand assembly. This is where the challenge is, production sized pads work great if you have a stencil printer and reflow oven. Hand application of paste will need clean-up, so give yourself a chance by making the pads big enough to get a soldering iron in there after reflow. Be careful with the center pad solder. If you get too much, the part will float and pull it away from the other pins.

author: zapta
author_rank: Super Contributor
timestamp: January 16, 2015, 05:31:56 pm
content: Quote from: Starlord on January 16, 2015, 02:31:18 pmI did a few HASL boards (elecrow) with QFN 0.5mm and no problem whatsoever (using 5mil metal stencil from elecrow) though ENIG (OSHPark) is definitely nicer.I used leaded paste, not sure if the HASL I got it leaded or not. You may want to look for match. Simpler with ENIG.For PCB price comparison checkhttp://pcbshopper.com.

author: nctnico
author_rank: Super Contributor
timestamp: January 17, 2015, 12:05:01 am
content: Gold plating is best for reflow. When hand soldering using an iron HASL is definitely easier to work with.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 17, 2015, 12:09:42 am
content: _good_ HASL is usually OK, but poor HASL can sometimes be lumpy, which is bad.For hand assembly it's not a big deal as you can always flatten any lumps with braid