Those dual package transistors are a bit of a pain! The hot air is for removing them, not installing. Tack down one pin first, then reheat it and align the transistor. After that, solder the rest. After that remove the shorts with some wick.
Most SMD gets easier with practice. These not so much! They are top heavy so they don't stay upright in the oven either.
Most SMD gets easier with practice. These not so much! They are top heavy so they don't stay upright in the oven either.
The industry must have a way with dealing with them. It's a neat idea but I think I would rather deal with installing the complimentary pair. I lost some so I am waiting for more to arrive so I can finish. I think I have all the parts for the VFA and CFA boards so I will finish those first.
Yes - we can have a matched (and thermally coupled) pair of npn+npn, pnp+pnp, or npn+pnp - whatever we need in particular case - suitable for virtually any kind of a front-end. Lots of freedom for designer.
But there must be some drawback. Difficult to solder manually 🙂 Even SMD opamps - like AD711 - are not that much of a problem as they are slightly bigger.
I'd love to have some more matched-dual or even -quad options available... some C3503/A1381 in a big 6-pin case would be great. As well as some sort of C1845/A992 and N5551/5401 pairs for higher-voltage application. Some jfet pairs would be great. K389 are not produced any more. Just dreaming 😉
But there must be some drawback. Difficult to solder manually 🙂 Even SMD opamps - like AD711 - are not that much of a problem as they are slightly bigger.
I'd love to have some more matched-dual or even -quad options available... some C3503/A1381 in a big 6-pin case would be great. As well as some sort of C1845/A992 and N5551/5401 pairs for higher-voltage application. Some jfet pairs would be great. K389 are not produced any more. Just dreaming 😉
I presolder one pad with a very thin layer.
Place and hold the component over the location and bring the soldering tip to that pre-soldered pad. Touching either the pad, or the leadout, tack solders the component to the board.
Then press down gently with a tooth pick, or needle, on the component and solder the other two lead outs.
Go back and finish solder the first lead out.
I find this never fails.
This method works great for 99% of SMD, but isn't particularly great for these dual package transistors that Terry is talking about. The package is so narrow that if you try to push down on it and reflow the solder, it will shoot out from under the toothpick and disappear on you. I've had a little better success holding onto them with tweezers, but still loose the odd one.
sot23, and soic 8pin all work by tacking one pin. I choose a corner pin.
And yes, tweezers work in holding them square to the pad layout and on pad as well.
But once the tacked pin is made there is enough strength left to allow a hold down method to work in keeping the pins on the pads ready for soldering.
I showed a pic some years ago of a wood & steel/pianowire hold down jig. This too works when on small PCBs.
And yes, tweezers work in holding them square to the pad layout and on pad as well.
But once the tacked pin is made there is enough strength left to allow a hold down method to work in keeping the pins on the pads ready for soldering.
I showed a pic some years ago of a wood & steel/pianowire hold down jig. This too works when on small PCBs.
Andrewt,
Have you actually soldered one of these bc846bpn units? I have done a few 8 pin devices but these are tiny. Getting them aligned is only part of it soldering the remaining pins is like micro surgery.
I would be very interested in seeing the ones you soldered. I have a hard time believing you have used them in any of your builds.
Have you actually soldered one of these bc846bpn units? I have done a few 8 pin devices but these are tiny. Getting them aligned is only part of it soldering the remaining pins is like micro surgery.
I would be very interested in seeing the ones you soldered. I have a hard time believing you have used them in any of your builds.
I get the feeling miniaturisation is only going to get worse. This weekend I am going to get a magnifying lamp so as I can get into some SMT projects. I probably need a smaller soldering iron too. There must be a thread on DIYA about tooling up for this.
is bc846 the same package?
Then yes.
soic 8pin is a bigger plastic package, the pins are closer together.
I have to wear 3dioptre spectacles AND look through a magnifying light.
I also have dental binoculars but have not got used to holding my head back that far from my hands when doing this small work. I should practice with them until I become proficient. They do give good magnification and a wide enough field of view once I got the optics much closer to my eyes.
I find the most difficult is tacking a 402 capacitor on top of another 805 capacitor. That is nearing my limit.
Then yes.
soic 8pin is a bigger plastic package, the pins are closer together.
I have to wear 3dioptre spectacles AND look through a magnifying light.
I also have dental binoculars but have not got used to holding my head back that far from my hands when doing this small work. I should practice with them until I become proficient. They do give good magnification and a wide enough field of view once I got the optics much closer to my eyes.
I find the most difficult is tacking a 402 capacitor on top of another 805 capacitor. That is nearing my limit.
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Yes those packages are easy. The one giving the trouble is a SOT363, which is much taller and top heavy, making it prefer to be upside down.
The little diodes sod123 like to fall over. And I did fire one off the bench and even managed to find it among the croppings I had not cleared up.
A Luxo with the round florescent tube works best. The "New Improved" modern day versions put out the wrong colour temperature which makes it more difficult to see the writing or orientation markings on components.
Actually a larger tip works better for finer lead sizes. fine solder is needed more so than a fine tip. Two irons are hand for quick removal of parts.
A guy I work with builds model ships and he recommended the florescent lamps too, said the leds are hard to work with. It was good luck as we talked about it this morning over coffee, I quickly googled the shop he recommended and they have a 33% off sale. They are not cheap, so I will head down first thing in the morning and get one at a good price.
Interesting I don't need a smaller tip. I have some fine solder so I may try soon. I don't plan on removal🙂
Interesting I don't need a smaller tip. I have some fine solder so I may try soon. I don't plan on removal🙂
I've seen pictures of Terry's bench top. It looks like mine. There's way too much junk from the 10 other projects going on at the same time to find anything that jumps off the board. If I do happen to find a part, I'm not actually sure if it's the one that just got away, so I throw it out and grab a fresh one.
LEDs aren't good at all. Lots of glare and blue colour. On Semi 1N4148WS orientation marking disappears completely under that colour.
It's not uncommon to need to adjust a resistor value from time to time. That's where the two irons works great. You can pluck a resistor off the board in a second, where the old through hole part meant desoldering and hoping you didn't damage a trace.
ah that's a good tip. So I probably will get another iron. My iron is 60W, is this not too much for these delicate parts?
Get a temperature controlled iron with replaceable tips.
I regularly use the smallest but the radius on the end is far too big. But it works.
I wish I could take a big tip and shape it to a chisel point, but I don't know how to iron plate it to cover up the reshaped copper.
I have a chisel point in my spares box, but it is not quite wide enough and the radius at the tip is too big. I want a real chisel POINT.
I regularly use the smallest but the radius on the end is far too big. But it works.
I wish I could take a big tip and shape it to a chisel point, but I don't know how to iron plate it to cover up the reshaped copper.
I have a chisel point in my spares box, but it is not quite wide enough and the radius at the tip is too big. I want a real chisel POINT.
As long as the iron has a good temperature control, 60W is fine. I have a couple Weller WES51s set to 700F on my bench. These parts are small, but they aren't delicate. They are meant to be soldered in an oven. They can take a lot of heat with no damage as long as it's done quickly, so a powerful iron is good.