Would better solder and a stencil help me here? - Page 1
Forum section: electronics / beginners

author: Jackster
author_rank: Frequent Contributor
timestamp: May 11, 2017, 10:43:58 am
content: Hi all.So I have made a few boards up but the problem atm is that I am not getting the best results in my reflow oven.Of which is just a toaster oven, without a reflow controller on it yet.The method I am using atm is one of those automated dispensers that use compressed air to push solder out of a syringe.The solder I am using is this;http://www.tme.eu/en/details/esn62pb36ag_40/solders-pastes/ag-termopasty/The results I am having look to be toasting the boards pretty well but not all of the solder melts.I am being quite conservative with my dispense of solder onto the board.The 0.5mm pitch components are the biggest struggle atm as they mostly require work after reflow.Even the 1mm pitch usually end up having a few pins short with solder.Should I just invest in stencil and a higher price paste?ThanksJack,

author: DTJ
author_rank: Super Contributor
timestamp: May 11, 2017, 11:39:44 am
content: Quote from: Jackster on May 11, 2017, 10:43:58 amI can't help with most of your questions but I use cheap leaded paste and the $10 laser cut stencils from pcbcart.comI pre-heat to around 110°C on a re-purposed kitchen hotplate and then wave a hot air rework gun over it until it melts.Even when fine stuff gets smudged it works fine with just a few rework spots.I used to place the paste manually but the stencil works better & I don't miss any pads.

author: rstofer
author_rank: Super Contributor
timestamp: May 11, 2017, 02:26:19 pm
content: It takes quite a while to heat the board, let it soak, ramp it up, hold and cool down. I built my reflow oven from a Black&Decker Infra Wave (now obsolete) but I had to add high temperature insulation in all the cavities in order to get to temperature. To me, this seemed critical.I also used a controller:http://www.rocketscream.com/shop/reflow-oven-controller-shield-arduino-compatibleIIRC, I modified the control algorithm a bit but this has been a few years back. Maybe there is a later version.If the boards are small enough, a hotplate works better:http://www.target.com/p/oster-single-burner-hot-plate-ckstsb100/-/A-13773420The problem is, the boards should probably not overlap that void area in the center. That rather limits the size of the board.You are not getting hot enough and/or you aren't holding at temperature long enough. The solder will flow when you get to a sufficient temperature for a long enough period of time.

author: KL27x
author_rank: Super Contributor
timestamp: May 11, 2017, 10:47:41 pm
content: QuoteI have this problem even at 0.65mm pitch and using full frame stainless steel stencils and a reflow oven. I'm looking for a better paste, so I'll be checking in on the thread. I am hoping a larger volume of paste will help too... even though my usage it not very frequent, I am thinking maybe the bigger jars are easier to use and to mix evenly before use.

author: rstofer
author_rank: Super Contributor
timestamp: May 12, 2017, 04:26:49 pm
content: http://www.howardelectronics.com/soldering/soldering-accessories/solder-paste-and-flux/qualitek/p615d-013-8840i-qi-qualitek-sn63-37-solder-paste/Unless I were to use a stencil, I wouldn't want solder paste in a jar. The syringe works well and other needles are available.

author: Jackster
author_rank: Frequent Contributor
timestamp: June 08, 2017, 01:41:33 pm
content: So I got a stencil and I think it helped.But I am having no luck with the oven side of things.I don't have a controller so I am having to do it by eye.The solder melts a little but not a lot.As you can see I overdid it to the point where the board melted >.<Any ideas on what I can do? Am I just going to have to buy a controller, maybe use some better paste?

author: rstofer
author_rank: Super Contributor
timestamp: June 08, 2017, 02:51:43 pm
content: As I said, I used the Black and Decker Infrawave but... In order to get it up to temperature in a reasonable time, I had to pack the wall cavities with high temperature insulation.Something like this, I believe:https://www.mcmaster.com/#additional-insulation/=17zag0wThe oven is no longer manufactured but there are others:https://www.amazon.com/black-decker-fc350-speed-cooking-countertop/dp/b00197vnyaFWIW, the InfraWave is rated at 1600 Watts and that isn't enough to heat up in the preferred profile without the insulation.I use leaded solder, it melts at a lower temperature (generally).I don't see how you can manually heat the board to a particular temperature (well below the melting point of solder), hold it at that temperature (soak) then ramp it up to melt the solder and hold for just a bit before ramping down (no heat added, in my case). This profile is pretty specific in terms of temperature and time.The hot plate approach is much easier: Turn it to Max, hold until you see all the solder melt and then carefully remove the board, setting it aside to cool. No profile, really, just add heat until the solder flows. Don't leave the board on the hot plate while it cools.There's a discussion of the suggested lead-free temperature profile here:http://www.rocketscream.com/blog/docs-item/reflow-controller-shield/It's pretty clear you aren't getting anywhere near hot enough and you need to get there fairly quick. Otherwise the board and components are damaged.

author: Jackster
author_rank: Frequent Contributor
timestamp: June 09, 2017, 02:16:32 pm
content: Turns out the paste I was using is shit for reflow at least.https://www.eevblog.com/forum/reviews/solder-paste-recommendation/msg965470/#msg965470Anyone got any recomendations on paste that they know that work that I can get in the UK?As in from RS, Farnell, TME etc?

author: Jackster
author_rank: Frequent Contributor
timestamp: June 09, 2017, 03:29:36 pm
content: Tempted to try this low temp stuff,http://cpc.farnell.com/chip-quik/smdltlfp/solder-paste-low-temp-5cc/dp/SD01716