SMD, reflow, beginner

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BennehBoy
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SMD, reflow, beginner

Post by BennehBoy » Thu Jan 25, 2018 2:14 pm

I'm considering venturing into making my own PCB's so I can use SMD reflow - my hand made veroboard monstrosities are testament to this requirement!

So, does anyone have any recommendations for a low(ish) cost startup which doesn't require an oven? I'm only going to be doing small stuff.

I was thinking to get a reworking hot air station - variable temp/air, any recommendations? I already have a decent temp controlled solder station but would consider a combined solution.

I'll probably initially be practicing my SMD technique using tssop to dip adapter boards and SS stencils readily available.
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Pito
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Re: SMD, reflow, beginner

Post by Pito » Thu Jan 25, 2018 2:26 pm

I did smds and BGAs with hot air, no stencil, no solder paste, but a lot of flux and pre-tinned pads only.. Needs some training to get the temperatures/air pressure/etc. right. BGAs yield 80% after some experiments..
For flatpacks/bgas you would need bigger nozzles (>=10x10mm). My settings (power/air_speed) were almost on the lowest ends all the time (2-3 out of 8), the distances 25-50mm when following a "profile" (distances calibrated with a thermometer, fixed power and air speed) with my 500W gun.
You cannot solder a pcb in one shot, however..
Pukao Hats Cleaning Services Ltd.

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mrburnette
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Re: SMD, reflow, beginner

Post by mrburnette » Thu Jan 25, 2018 4:20 pm

between the hotplate with a sand head moderator and a hot-air rework station, you should do OK. I have an inexpensive rework station that is a real workhorse.

But, the high-quality rosin flux is the trick. Easy cleanup with IPA (90% or better) ... then use the hotair to remove all of the moisture, or bake the board. If you need a conformal coating, apply after baking the moisture.

zmemw16
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Re: SMD, reflow, beginner

Post by zmemw16 » Thu Jan 25, 2018 4:23 pm

flux, flux and more flux.
make you clean it off afterwards
srp

victor_pv
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Re: SMD, reflow, beginner

Post by victor_pv » Thu Jan 25, 2018 7:20 pm

BennehBoy wrote:
Thu Jan 25, 2018 2:14 pm
So, does anyone have any recommendations for a low(ish) cost startup which doesn't require an oven? I'm only going to be doing small stuff.
Not sure where you are located, but in the US you can buy a toaster over from some $50 and you can reflow with low temp solder without any modification whatsoever, just like it comes from the factory.
I only tried low temp solder sn45pb35bi20 before I started modifying it, but reflowed just perfect.
This oven (I bought from amazon though)
https://www.walmart.com/ip/BLACK-DECKER ... B/15806193

Key points, get more one uses more than 900w to get a good temp quick, and that has a fan (normally described as "convection" ones).
How I used it: I reflowed a board 100x100mm with that paste and like I took it out of the box. That solder paste melts at some 180C and the over had no problem reaching that. The Fan helps to spread the heat to all components and the PCB.

First I preheated to oven 100C with the board inside already, kept it there a couple of minutes, then I set the oven to some 200C, and watched thru the door and could see the solder melting. Once the solder was melting I counted like 1 minute, then turned it off and opened the door to let it cool down.
I first tried some smaller boards, no trouble, then one that's 100x100mm, no trouble again.

With higher temp solder you need to be more precise to not damage anything, so I have modified the oven with insulation, a bluepill as controller with thermocuple, SSR for the heating and SSR for the fan, etc, but I haven't had the chance to resolder anything yet.

I tried the skillet method before, too much trouble, the oven is way easier. I don't think you can beat it for $50 or less.

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RogerClark
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Re: SMD, reflow, beginner

Post by RogerClark » Thu Jan 25, 2018 8:08 pm

Don’t buy a T-962 reflow oven from eBay etc, they are junk...
I have one nx it’s still uslwss even after spending weeks upgrading the firmware and sensors etc etc

It’s main problem is very uneven heating as the heating elements are within 5 cm of the board

It needs to have an internal fan added , but that’s a major mechanical modification that I have not had time to make.

So my T-962is in the shed in pieces at the moment, and is likely to stay there for the foreseeable future

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BennehBoy
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Re: SMD, reflow, beginner

Post by BennehBoy » Thu Jan 25, 2018 10:08 pm

So basically I should get an oven?

The problem is that I have a HUGE amount of what my wife would term 'sh*t' already in the house...

All my electronics gear

A ton of computer and hi fi gear

Even more camera equipment, ranging all the way up to 8x10 & a fully automated colour autolab.

All manner of automotive tools and test gear (granted most of it is in the shed).

So getting 'yet another' non trivial piece of kit is probably not going to help.
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zmemw16
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Re: SMD, reflow, beginner

Post by zmemw16 » Fri Jan 26, 2018 11:34 am

plenty of camouflage then :lol:
trick is to make the recent project item nearest to you be something else.
not sure which would be harder, a missus or the bank ;)
srp

victor_pv
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Re: SMD, reflow, beginner

Post by victor_pv » Fri Jan 26, 2018 8:55 pm

Another good trick is to make some projects for her. Then when you need tools, parts, whatever else, you can always say it's needed to finish HER project ;)
I'm building my wife a flamenco guitar, which I enjoy building anyway, but since I started building hers I have heard zero complaints about the piles of guitar wood and tools I have. You would think they became invisible!

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ahull
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Re: SMD, reflow, beginner

Post by ahull » Fri Jan 26, 2018 9:38 pm

victor_pv wrote:
Fri Jan 26, 2018 8:55 pm
Another good trick is to make some projects for her. Then when you need tools, parts, whatever else, you can always say it's needed to finish HER project ;)
I'm building my wife a flamenco guitar, which I enjoy building anyway, but since I started building hers I have heard zero complaints about the piles of guitar wood and tools I have. You would think they became invisible!
I'm hoping to use a similar ruse to justify my new 3D printer, lots of "knitting needle gauges" and other similar projects will need to be included in its output. :D

I'm also hoping to build a few fancy new "combs" for some of the more ancient, beat up and dilapidated harmonicas I've collected over the years, and print off some simple overblown flutes in different keys. (More details)

This is all, in reality, an excuse to waste a lot of time playing with FreeCad, and of course, making "a mess", which is one of the few things I seem to be supremely talented at.
- Andy Hull -

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