Suitable rework station to remove and replace parts like L6205PD H-Bridge

[perdrix]

I needed to replace one of these yesterday, and with the tools I have it was an absolute PITA to remove.

In the end I used a carbide mill to cut the entire top of the IC to reveal the large copper substrate which was soldered to a copper ground plane on the PCB (about 16mm by 10mm).   In the process I did a bit of damage to some of the pads and adjacent tracks (which I can work round with some bodge wires).

To solder in the replacement I've drilled a couple of 3mm holes through the board so I can solder the heat sink plane from underneath.

I'm likely to need to do this again, so next time however I'd much prefer to do this properly !!!  I don't think using a domestic oven ist appropriate as the PCB has quite a fair number of thru hole parts with plastic housings that really wouldn't be happy with 200C.  Maybe I'm over worrying about that though???

So, given a very limited budget (he says) what should I be looking at in the way of rework stations?  Probably used, and not too large!

Are the T862++ units I see on eBay any good or would that be a waste of my cash?  If not those, then what?

Thanks
David

[perdrix]

Anyone with thoughts about the more affordable IR solder stations such as the type I referenced? Anyone?

Thanks
David

[Rasz]

Anyone with thoughts about the more affordable IR solder stations such as the type I referenced? Anyone?

bottom heater is 120x120mm, great for cellphones, useless for anything bigger. you will risk pcb deformation
240x60mm panels are $10 from China, buy 3-4 + $15 REX-C100 clone PID controller (bundled with thermocouple and SSR) and you have bottom half of proper BGA station.

[telectric]

Yeah, these are tough to get off.  I usually cut all the legs first and then take a 140W soldering iron/pencil (sometimes two) and remove the body.  Then go back with a small iron to remove the legs.  Clean the solder off with solder wick. Then pre-heat the new part in an oven staying within the manufacturers temperature range. When it's good and hot move it onto the board & use the 140W iron again to solder it to the copper.  Then go around and solder the leads.
Not sure if this will work for your situation but I thought I'd share a process that has been useful to me.

Regards, Tracy

[nctnico]

For these kind of jobs I have a Atten 585D hot air gun and a hotplate. To heat a PCB locally I put a piece of aluminium on the hot plate to transfer heat where it is needed most and heat the rest of the PCB slightly.

[Rasz]

To heat a PCB locally I put a piece of aluminium on the hot plate to transfer heat where it is needed most and heat the rest of the PCB slightly.

this is how you damage pcbs, you do want to preheat whole thing uniformly and relatively slowly

[bdunham7]

So, given a very limited budget (he says) what should I be looking at in the way of rework stations?  Probably used, and not too large!

Are the T862++ units I see on eBay any good or would that be a waste of my cash?  If not those, then what?

Thanks
David

Here's some thoughts, but keep in mind I'm no kind of pro and others here have more experience.  My situation is I will occasionally want to fix something and it is usually unobtanium so I really, really don't want to damage it and I have all the time in the world--and I'm very patient.

First, I've no experience with the top-focused IR systems like the one you mentioned.  You didn't mention what tools you do have, but I think you need a bottom preheater and a hot air station.  The IC you are replacing is a monster so it might be a bit trickier doing it with bottom-of-the line entry level tools, but if your budget is near zero try these:

https://www.ebay.com/itm/T-8280-IR-PCB-Infrared-Preheater-BGA-Rework-Preheating-Station-1600W-280x270mm/124088274624?hash=item1ce43ccec0:g:Ag8AAOSwzjxeS-B9

https://www.ebay.com/itm/Hot-Air-Gun858d-700w-Bga-Rework-Station-Soldering-Heat-220v-110v-Smd-Smt-Welding/143348030227?hash=item2160355b13:m:m2_9xJJRJPB7Gc9Hu8q1XDw

There are smaller preheaters available for less and the 858D hot air station is available in many places.  Just make sure and throw away any 'free' solder you get with it. 

With large or thick devices like that on irreplaceable boards I will take the legs off first by very carefully cutting them at the body and then sucking them off with a desoldering gun.  If you don't do this, when you start wrestling the chip off it is possible for the heat sink and most of the legs to come loose while one leg in one corner hasn't melted yet and then you lift or tear a pad.  Once the legs are off, you can very very very carefully grind the chip from the top if you want, but this takes the right tools and patience.  A drill press, a cross feed vise and an end mill will work.  A carbide burr on a air-powered die grinder will be a disaster unless you are as strong as The Hulk and as steady as a Swiss watch maker, which I'm not and from your description of how things worked out, neither are you.  With anything near the proper tools you can skip the grinding.

Once you have it off, in some cases it may be helpful to use a lower temperature solder on the heat sink part.  There are indium and bismuth based silver solders that are $$$ but work very well and lessen the need to cook an expensive board any more than necessary. 

https://www.mouser.com/ProductDetail/Chip-Quik/TS391LT?qs=1mbolxNpo8dzjCIcP7S2Kg%3D%3D&gclid=CjwKCAjw5Ij2BRBdEiwA0Frc9XGENCsWXg8pJ2432oPVq9e-2y7-XOI_fKNiCcRVqv6sHinKEZb3yhoCZWMQAvD_BwE

Anyway, I hope that helps and that your budget is at least $200, because the tools I've suggested are about as cheap as I can imagine for getting that job done decently.

[wasyoungonce]

Ok in same boat as OP perdrix same IC ........same PCB.

I removed the SO20 package ok...grind it away to expose metal substrate and GND base tab.  Then de-solder leftovers came away easily.  Still, a hair raising task!

Ok now the hard part, soldering a new one back.   It's a 4 Layer PCB inbetween are 3.3V and 5V planes.  The Top has a decent top and bottom GND pad under the package with plenty of vias thru.

I'm thinking I can wet the SO20 package GND plate then use the end tabs with twin irons to reflow.  Testing showed this possible but that wasn't with the PCB GND planes.  Maybe I should be trying a lower melt solder paste?  Should I?  Only ever use chipquik for removal and its too low temp for this application.  Maybe other pastes?

I also tried a big 120W iron "Bertha" from under and can get the top GND plane to solder melt in around 20 seconds.  This is pumping heat thru all layers this I noted.  Maybe I can pre-heat with this.

I've read ST TN1258 tech notes info on SO20 packages and reflow but they don't mention how!  Do I use the end tabs, see picture?  I guess I preheat the PCB with Bertha then use the end tabs.....but I'm so unsure its a package that has me past my comfort level.

I do have a hot air station....FWIW.

Any ideas on fitting new IC down welcome (low temp paste?, pre-heat?, use Bertha?, use the end tabs and twin irons?)...like perdrix expensive IR reflow is out of the question...help me I'm poor!

Edit: to wrap up I tacked the legs, removed that capacitor near the top of the IC to allow twin irons on the IC Tabs.  I solder wet the underside of the IC plate,  used large wattage iron under on GND plane to heat thru to the top and went for it to reflow the plate wetting to the GND plane. 

Ok it worked but there was too much heat IMHO.  Ok it’s all now working fine but I won’t do it that way again.  Just too much heat. Might get some 138C low melt paste 

[perieanuo]

hi,
any low-cost reflow china stuff does it perfectly, if you have the apropriated nozzle
I use for everyday work atten 8502d for example, but I used also cheaper stuff.
if you have the luxury of a heating plate (on the bottom side, I manufatured myself one with a thermo-regulator and 2 rectangular alu plates, between those plates I inserted 2 heating resistors totally 1600w, but i regulate to 80-100 degrees celsius the temp), it just becomes 10 times easier
the right nozzle is the secret for heating only the right component needed to be desoldered

[wasyoungonce]

Many thanks.....yes thinking of a thermo plate but it kinda wont always suit, these PCBs have a large amount of parts populated under.  They did leave this area clear.

I Heard from factory repairers...they use hot air stations.  I have an 858 hot air station. I didn't use it as I'm not good with it and I though it would have taken much longer to reflow than the large iron did.  The Hot air is probably better controlled temperature than my 120W iron!   I think my error was adding twin iron on the H bridge tabs.   I don't think it was needed.

I think i need a better hot air station.  QUICK 861DW...and learn to use it ...not just for heatshrink!
https://www.eevblog.com/2018/02/20/eevblog-1058-quick-861dw-hot-air-rework-station-review/

cheers