Basic Things to avoid when manufacturing or assembling pcbs - Page 1
Forum section: electronics / general

author: mendez
author_rank: Regular Contributor
timestamp: February 26, 2019, 04:28:31 am
content: What are the basic things to avoid when you are trying to solder , use pick and place and reflows pcbs?Ex. I realize that i cant wear a winter coat, because it generates a lot of static charge and i hate wearing the anti static band. But is there any other things that you should consider?Like...pick and place must be in a temp. Control room?

author: Reckless
author_rank: Frequent Contributor
timestamp: February 26, 2019, 07:52:00 am
content: We run my pick and place machines at 55 F. I don't recommend that but it can be done. Solder paste can get dry quick so don't let it sit too long. Don't inhale fumes as much as possible. Be careful not to cook pcbs.

author: ANTALIFE
author_rank: Frequent Contributor
timestamp: February 26, 2019, 08:11:31 am
content: If you are reflowing solder with something that does not follow the typical JEDEC profile, make sure to let flux evaporate before the solder start melting. Otherwise you are going to witness some annoying component gymnastics as the flux vapor creates enough force to throw some components off your board ;^)

author: SMTech
author_rank: Frequent Contributor
timestamp: February 26, 2019, 08:56:03 am
content: Things like pick and place equipment have a fairly narrow window at which their rated accuracy is valid and is around the standard room temp of 21C (unsurprisingly). That is not to say they don't work perfectly well slightly outside these temps but then you('re) employees will not. A reasonably consistent temperature also means your paste behaves in a predictable manner which will help with consistent printing results, many pastes require storing cold but bringing up to room temp slowly before use, you really don't want to be trying to use paste at 55F (12.8C). A modern production floor would typically be climate controlled but whether yours needs to be would depend a bit where you were, surely 100% necessary in Florida and more easily avoided further north.Anti static: yes wriststraps are annoying and don't work well if you are not working at a workstation, which you wouldn't be if running a mini production line. But its not something you can simply not have so you could instead equip your room with antistatic flooring benches & seats and wear a footstrap.Keep the room clean.Keep the room ventilated, make sure fumes from reflow are extracted, they stink and if you see the crap that builds up in an oven (or filters if it has any) you don't want to be breathing in.

author: mendez
author_rank: Regular Contributor
timestamp: February 26, 2019, 02:25:27 pm
content: Thank you all for the feedback!When I solder or apply solder paste I use the Hakko FA-430 and its seems to do a great job; And I also keep my solder paste in the fridge before I use it.1. As far as the Pick and Place (PnP); I know it really depends on the brand; but, can I left the PnP in a cold garage (30F) overnight? or it might not be recommended due to the vision camera?2. SMD Storage? I just buy those antistatic sorage box and keep them in a temp. control room (inside the house) ?

author: SMTech
author_rank: Frequent Contributor
timestamp: February 26, 2019, 03:32:26 pm
content: For a little PNP you can probably do whatever you like, their tolerances are nowhere near anything that might affect accuracy due to temperature IMHO. You probably don't want to keep it anywhere it might freeze or get condensation on tho'.Your enemy is likely to be moisture, many electronic components love to absorb moisture, if it isn't controlled or baked out slowly they can go pop when you reflow them. For low volume you might just be talking keeping them stored with some desiccant packs in something airtight, here in the UK I've never encountered a problem even things I know have been stored outside of spec so your mileage may vary. However out factory is heated with a massive gas fired blower which probably keeps things dryer than might otherwise be true.

author: jmelson
author_rank: Super Contributor
timestamp: February 26, 2019, 09:54:38 pm
content: Quote from: mendez on February 26, 2019, 02:25:27 pmI REALLY would NOT do this! I wouldn't worry about the camera as much as condensation on the machine during temperature changes. Keeping it in a garage is like keeping it OUTSIDE! One other thing, if you have stored boards for a long time before stuffing/reflow, you might want to bake the moisture out of them to prevent blistering. I heat to 50 C for an hour, then 70 C for an hour, then no blister problem.Jon

author: jmelson
author_rank: Super Contributor
timestamp: February 26, 2019, 10:04:55 pm
content: I have tried the ChipQuick, and it worked pretty well. But, I do a lot of lead-free work. I have started using GC10 (sold in the US under the Loctite brand) and it is amazing stuff. I just did some boards with about 8400 SMT solder joints, and I had **ONE** bad joint in the whole batch. That is absolutely a record for my homebrew setup.Jon

author: olkipukki
author_rank: Frequent Contributor
timestamp: February 27, 2019, 12:18:59 pm
content: ChipQuick is a good paste, but was short-life at last time I used it and waited almost 6 weeks thought a distributor.Now they make "no fridge" version with shelf life more than 12 months and in a small jars.*Also, looks like you can order directly.* not yet tried

author: Psi
author_rank: Super Contributor
timestamp: February 27, 2019, 12:24:14 pm
content: 1) I had some T3 chipquik paste that worked fine and some T5 paste that was damn awful.I recommend getting something better. Chipquik is usually the lowest cost stuff for a reason.2) Have a large tray setup with all your paste soldering gear on it and do everything on this tray. Then put the whole tray away when your done. This keeps you from getting solder paste everywhere.It's much easier to clean up when its all in once place.Since it's a 'paste' it's easy to get it on your fingers and then start touching stuff and before you know it you have lead paste everywhere. Really bad3) Wear nitrite gloves for above reason. It makes clean up easy. And a box of 50 is pretty cheap.4) If you the paste explodes when you reflow it, eg parts jump off the PCB then your paste is bad. Throw it out and get some new stuff as it has got water in it.5) Store the past in a fridge. but be careful, you don't want to contaminate your food fridge with lead. You can store it safely in a food fridge if careful but if others use the fridge i wouldn't risk it. Get a small fridge dedicated for solder paste and glues. You don't want to come home to find your wife/gf has baked a cake and iced it with some awesome silver icing she found in the fridge.

author: olkipukki
author_rank: Frequent Contributor
timestamp: February 27, 2019, 12:38:42 pm
content: Quote from: Psi on February 27, 2019, 12:24:14 pmWhere is it? I found same pricing as GC10...

author: Psi
author_rank: Super Contributor
timestamp: February 27, 2019, 12:59:17 pm
content: Whenever i order by price chipquik is in the first few results.

author: olkipukki
author_rank: Frequent Contributor
timestamp: February 27, 2019, 01:39:35 pm
content: Quote from: Psi on February 27, 2019, 12:59:17 pmHow much did you pay for ChipQuick and CG10 in NZ?Here we go, for example, Mouser NZ pricing for 250gr lead-free no clean T4 (500gr approx 90% of 2 jars)

author: SMTech
author_rank: Frequent Contributor
timestamp: February 27, 2019, 02:48:53 pm
content: That's some expensive paste. That said it is often better to source your paste from specialist suppliers, in the UK you might buy Henkel/Loctite GC10 from Grosvenor for less than Farnell, BLT directly, Warton directly, DKL from Surclean (DKL want to sell you a crate of the stuff directly) & Koki from Fraser technologies for instance. The downside paste is heavy and those people will probably charge shipping, we single source everything from BLT- bar,wire,paste,wipes&flux

author: mrpackethead
author_rank: Super Contributor
timestamp: February 27, 2019, 06:58:09 pm
content: GC10 is avaialble from both synergy electronics and Baskiville in New Zealand. they have it in stock. $NZ108+GSThttps://www.baskiville.co.nz/products/category/ALL/HEN2001184--loctite-henkel-gc-10-sac-305-type-4-solder-paste-500-grams

author: mendez
author_rank: Regular Contributor
timestamp: February 28, 2019, 02:29:57 pm
content: Thanks guys for the feedback. The solder paste will have its own fridge from now on! and I will store the smd components inside the room.Question: When I'm applying solder paste to my boards; I can still smell the fumes of solder paste; I even tried to point my Fakko FA-430 as close as possible to the pcb but still. Is there a way to avoid the fumes at all? even on a open environment you can still smell it. When I solder, the FA-430 does a great job; but applying solder paste is the issue.Thanks,Jose

author: jmelson
author_rank: Super Contributor
timestamp: February 28, 2019, 08:05:27 pm
content: Quote from: mendez on February 28, 2019, 02:29:57 pmGee, I haven't noticed any smell AT ALL when applying the paste. Now, when I do the reflow in the oven, then I DO smell it, and the GC10 stuff is so strong I'm going to have to build a fume hood to suck up the fumes.Jon

author: mendez
author_rank: Regular Contributor
timestamp: March 01, 2019, 12:01:31 am
content: Thanks, I will have to try the Lead free paste then.