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As I await receipt of my lifetime shipment of BSS123 MOSFETS to try to bring my QDX receiver back to life after an apparent ESD incident caused by lightning, I am contemplating how I am going to remove the old BSS123 devices without damaging the QDX circuit board.
If I just try heating the pins with my soldering iron and simultaneously lifting the device with tweezers, what temperature would you guys with experience recommend? I usually run the soldering iron at 750F (400C) when I build kits and that seems to work fine, but perhaps a lower temperature would be best for SMD removal....any advice appreciated! Also, should I use solder wick or is that not a good idea? I have not had good experiences with a "solder sucker' iron that I own, so I do not plan to try that approach.
I also have a heat gun which I use for heat shrink tubing which probably could be used to melt solder on all three pins simultaneously, but I am concerned that the heat might cause problems with other components on the board since the hot air cannot really be focused on the component that I am trying to remove,..any experienced heat gun users out there who can offer advice?
I am hoping that installation of the new BSS123 devices will be relatively painless, but nothing is easy in the world of electronics.
Thanks,
Ed, K0KC
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Ed
Glad you are up for adventure. My experience removing surface mount devices is to add just a little solder to each pin, and warm them until it's swimming on the solder, then flick the part off its pads. I think best to localize the heat, as some parts have lower temperatures where they literally come apart.?
Curt
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Ed,
I have had very good results using "ChipQuik". It has a low melting point and can be used to remove SMDs without damage. There are You Tube videos showing how to use it.
Lou? W2ROW
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Ed, I bought a fairly inexpensive rework station similar to the one in this link. It works well.
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73, Dan - W2DLC
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the hot air cannot really be focused on the component that I am trying to remove,.. Ed, My method is to use aluminium foil. Cover all except the component. Make sure you make it hot enough so the solder is definitely melted before lifting off. Capacitors/resistors maybe use two soldering irons. I've never tried on a transistor but perhaps a biggish bit would cover two pins. 73 Alan G4ZFQ
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The Chip Quik Kit can be purchased from eBay ($15-20) free shipping or Amazon ($11) shipping free if total Amazon stocked items over $25.
This is my smile link and it may not work for you, if not, then just search for ¡°Fast Chip¡± I got the $10.99 package.
John
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On Jun 15, 2022, at 09:03, Daniel Conklin < danconklin2@...> wrote: Ed, I bought a fairly inexpensive rework station similar to the one in this link. It works well.
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73, Dan - W2DLC
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Kapton tape works as a temporary heat shield as well. Since I don¡¯t try to save 2 pin devices I just heat them up till both pads melt and they stick to the iron. 650F is plenty hot for this. I solder back on at about 600F.?
For the three pin devices I can pull with tweezers as I go around and hit each pin till they are all loose at once.
For ICs I use hot air with the smallest tip and a low air flow. My air station is in C and 260C works for chips you are going to toss. If I am saving a chip I read the specs on the data sheet about max heat.?
Colin - K6JTH?
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Thanks for all of the suggestions Curt, Lou, Dan, Alan, and John!
I am going to try "ChipQuik" first and then if I do not like the results, I may order the solder re-work station. The foil suggestion is interesting as well, but we will see how the other methods work. I may end up replacing 4 MOSFETS (Q3, Q4, Q5, and Q6). It appears that Q3 is bad for sure and perhaps the others will need replaced as well...we shall see.
Ed, K0KC
k0kc@...
http://k0kc.us/
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More good advice from Colin and JP!
I will let the group know how I make out with this SMD device removal and if it fixes the QDX.
Ed, K0KC
k0kc@...
http://k0kc.us/
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Lots of good advice, but I think if I needed to remove one or two surface mount 2 legged parts I would wrap a short piece of #14 bare, solid copper wire around my iron tip (or remove the tip and incert the folded end of #14) into the iron, then with two ends of the #14 making a fork about 3/4" long and spaced the width of the SMD, I could unsolder both solder joints at the same time, flipping the componet away with a tooth pick. Pete W4WWQ
More good advice from Colin and JP!
I will let the group know how I make out with this SMD device removal and if it fixes the QDX.
-- Pete Lascell
Forest, VA
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I use 2 soldering irons at the same time, works a treat Geoff GI0GDP
On Wednesday, 15 June 2022, 20:36:05 BST, Peter Lascell <plascell@...> wrote:
Lots of good advice, but I think if I needed to remove one or two surface mount 2 legged parts I would wrap a short piece of #14 bare, solid copper wire around my iron tip (or remove the tip and incert the folded end of #14) into the iron, then with two ends of the #14 making a fork about 3/4" long and spaced the width of the SMD, I could unsolder both solder joints at the same time, flipping the componet away with a tooth pick. Pete W4WWQ
More good advice from Colin and JP!
I will let the group know how I make out with this SMD device removal and if it fixes the QDX.
-- Pete Lascell
Forest, VA
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Removal of two legged devices?? The easiest way is with two grounded/ESD soldering irons.? (or hot tweezers but honestly two irons are easier).? You can get many three legged devices that way too...one iron gets two leads in that case.? Once the solder flows grab the device case with the irons or sweep the device if you can off the board.?
I thought you guys were talking about something difficult!? :)?
More than that, heat gun and tweezers or low temp alloys like chip quik.
Always, always, always... when doing smt work, use a generous amount of quality liquid flux. It's a game changer.? Trust me.?
Don't panic, once you learn the tricks smt work and rework can be easier than through lead.
Hardest part for us bifocal guys is to see what we are doing...
Fred W0FMS?
On Wed, Jun 15, 2022, 12:35 PM Peter Lascell < plascell@...> wrote: Lots of good advice, but I think if I needed to remove one or two surface mount 2 legged parts I would wrap a short piece of #14 bare, solid copper wire around my iron tip (or remove the tip and incert the folded end of #14) into the iron, then with two ends of the #14 making a fork about 3/4" long and spaced the width of the SMD, I could unsolder both solder joints at the same time, flipping the componet away with a tooth pick. Pete W4WWQ
More good advice from Colin and JP!
I will let the group know how I make out with this SMD device removal and if it fixes the QDX.
--
Pete Lascell
Forest, VA
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Have used chip quick to remove and reuse an ATMega328P and it does work well.
But for small stuff I think the easiest to get and probably cheapest is a basic low cost no frills not temperature controlled low watt soldering iron for minimal money from Walmart or Harbor freight. Being able to heat both sides of something at the same time by using two irons is a big advantage. If there are multiple pins you may need to flood that side with solder and clean up later. I tried a fancy two flexible prong soldering iron and surprisingly two separate irons is easier and works better. The part will stick to one of the two irons after you pick it up, you can scrape or flick it off if you are worried about toasting it and might want to reuse later. You will need a place to also park the second hot iron.?
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Hi, Fred
When I was still fixing early digital RCA projection TV power
supplies, I used paste flux because, when working on a vertical
circuit board, it would hold the transistor in place long enough
to tack one of its little leggies. If I remember correctly, there
were 3 smd transistors that would be popped in the SMPS, and
getting the board into a "face down" position was a bear.
73
Jim W4JED
On 6/15/22 15:51, Fred Spinner wrote:
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Show quoted text
Removal of two legged devices?? The easiest way is
with two grounded/ESD soldering irons.? (or hot tweezers but
honestly two irons are easier).? You can get many three legged
devices that way too...one iron gets two leads in that case.?
Once the solder flows grab the device case with the irons or
sweep the device if you can off the board.?
I thought you guys were talking about something
difficult!? :)?
More than that, heat gun and tweezers or low
temp alloys like chip quik.
Always, always, always... when doing smt work,
use a generous amount of quality liquid flux. It's a game
changer.? Trust me.?
Don't panic, once you learn the tricks smt
work and rework can be easier than through lead.
Hardest part for us bifocal guys is to see
what we are doing...
Fred W0FMS?
On Wed, Jun 15, 2022, 12:35 PM
Peter Lascell < plascell@...>
wrote:
Lots of
good advice, but I think if I needed to remove one or two
surface mount 2 legged parts I would wrap a short piece of
#14 bare, solid copper wire around my iron tip (or remove
the tip and incert the folded end of #14) into the iron,
then with two ends of the #14 making a fork about 3/4"
long and spaced the width of the SMD, I could unsolder
both solder joints at the same time, flipping the componet
away with a tooth pick.
Pete
W4WWQ
More good advice from Colin and JP!
I will let the group know how I make
out with this SMD device removal and if it fixes
the QDX.
--
Pete Lascell
Forest, VA
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Another up-vote for desoldering alloy.? I've used this product
with very good results.? I've had to replace ATmega328 microcontrollers twice, and each one involved harvesting a donor chip from a development board since you currently can't buy these MCUs at reasonable prices and with quick delivery.
Full story here:
???? I fried my ATmega328p (Fixed thanks to KI6NAZ's story)
After removing a bad chip with the alloy I'm careful to clean the PC board pads up with solder wick, to get rid of the remaining desoldering alloy.? And since I had to harvest an ATmega328 from a donor board I cleaned up the pins of the replacement chip using solder wick.
Works well and saves me from buying a hot air rework station and having Yet Another Rarely Used Tool around.
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It's even getting difficult to get 328Ps?? We live in interesting times...
With a dip device what you did with the chip quick type alloy is probably the best, even hot air is a bit dicey with something that big also with the friction of the leads going through the boards.?
Having?said that, a $30 Chinese heat gun is something you will use once a year for rework or smt work but several times a month for heat shrink, setting epoxy and stuff that you wouldn't even imagine.? I recommend having that tool available, they really don't take up that much space.? Like my soldering irons, I also have two of those on my desk.?
Fred W0FMS?
On Thu, Jun 16, 2022, 7:28 AM Rich Brandt, AE8AA < richbrandt@...> wrote: Another up-vote for desoldering alloy.? I've used this product
with very good results.? I've had to replace ATmega328 microcontrollers twice, and each one involved harvesting a donor chip from a development board since you currently can't buy these MCUs at reasonable prices and with quick delivery.
Full story here:
???? I fried my ATmega328p (Fixed thanks to KI6NAZ's story)
After removing a bad chip with the alloy I'm careful to clean the PC board pads up with solder wick, to get rid of the remaining desoldering alloy.? And since I had to harvest an ATmega328 from a donor board I cleaned up the pins of the replacement chip using solder wick.
Works well and saves me from buying a hot air rework station and having Yet Another Rarely Used Tool around.
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Harbor Freight, I use it for a mixture of tasks. $16.99 + tax? Paul K2DB
On Thu, Jun 16, 2022 at 10:28 AM Rich Brandt, AE8AA < richbrandt@...> wrote: Another up-vote for desoldering alloy.? I've used this product
with very good results.? I've had to replace ATmega328 microcontrollers twice, and each one involved harvesting a donor chip from a development board since you currently can't buy these MCUs at reasonable prices and with quick delivery.
Full story here:
???? I fried my ATmega328p (Fixed thanks to KI6NAZ's story)
After removing a bad chip with the alloy I'm careful to clean the PC board pads up with solder wick, to get rid of the remaining desoldering alloy.? And since I had to harvest an ATmega328 from a donor board I cleaned up the pins of the replacement chip using solder wick.
Works well and saves me from buying a hot air rework station and having Yet Another Rarely Used Tool around.
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Or an "embossing" tool from any craft store and even some Walmarts.
My argument against those are that they are like $5-10 less than a purpose built air rework from China, and they don't have temperature control.?
Harbor Freight, I use it for a mixture of tasks. $16.99 + tax? Paul K2DB
On Thu, Jun 16, 2022 at 10:28 AM Rich Brandt, AE8AA < richbrandt@...> wrote: Another up-vote for desoldering alloy.? I've used this product
with very good results.? I've had to replace ATmega328 microcontrollers twice, and each one involved harvesting a donor chip from a development board since you currently can't buy these MCUs at reasonable prices and with quick delivery.
Full story here:
???? I fried my ATmega328p (Fixed thanks to KI6NAZ's story)
After removing a bad chip with the alloy I'm careful to clean the PC board pads up with solder wick, to get rid of the remaining desoldering alloy.? And since I had to harvest an ATmega328 from a donor board I cleaned up the pins of the replacement chip using solder wick.
Works well and saves me from buying a hot air rework station and having Yet Another Rarely Used Tool around.
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?? Definitely use SRA Fast Chip!!!!? It's a special eutectic metal alloy with the property that the mixture has a lower melting point that any of it's component alloys!? Works great for anything SMD!!!? Website for the solder/desolder kit with special flux is at sra-solder.com according to the packaging.? Definitely use SRA Fast ChipI Also UTube tutorials on this.
?? I also went on EBay and found a SMD training kit that contains SM UProc ICs, DIP ICs, transistors, resistors, & caps and a training PCB.? The training kit is absolutely invaluable if you want to learn about SM technology!!!!? And it is cheap!? Great learning tool and I advise it for anyone who has no SMD experience and wants to learn!!!
??? I had a QRPLabs 40m rig that I was working on when I made a mistake with a few solder through hole components that I had to replace.? Trouble was the holes in the PCB were so small that I could not get all the solder out of the holes using my solder sucker and the pin inserted into the melted solder hole method. As a last resort I filled the holes with Fast Chip solder and now I could use solder wick or my dental pick to clean out the holes.? So I guess this Fast Chip has other useful applications!!
73 wt1v
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On Wed, Jun 15, 2022 at 08:35 PM, Peter Lascell wrote:
Lots of good advice, but I think if I needed to remove one or two surface mount 2 legged parts I would wrap a short piece of #14 bare, solid copper wire around my iron tip (or remove the tip and incert the folded end of #14) into the iron, then with two ends of the #14 making a fork about 3/4" long and spaced the width of the SMD, I could unsolder both solder joints at the same time, flipping the componet away with a tooth pick.
Pete W4WWQ
Agreed. I did just that when I needed to remove an smd transistor in a uBitX. It works a treat. One leg heats two pins of the transistor and the other leg heats the pin on the other side. (pins.... I mean tiny little projecting bits ? >:-)?? ? ? ?? ). I practised by removing smd caps and resistors from an old circuit board......?? easy as shelling peas. Reg????????????????????????????????????? G4NFR ?
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Daniel Conklin
KK4ITX John
Colin Kaminski
Fred Spinner
James Daldry W4JED
K2DB Paul Mackanos