CMKT5088 - Dual NPN for *2*5*2*0* input

[tk@halmi]

I may have found the transistors that are used on the input of the new *2*5*2*0*. It is a dual NPN (matched!!!), the CMKT5088 from Central Semi. The trouble in using them: they are in SOT-363 cases, about the quarter the size of a peppercorn. When I first opened the package from Central Semi I thought they forgot to put something in the plastic bag, then lifting the bag to the light I saw these tiny little things. You may have to go to a surface mount house to get them isntalled. Does anyone have experience with soldering SOT-363 packages? Special equipment, tricks?

Tamas

 

[Bauman]

Cool! Magnifing lens is the first thing you need...

 

[SonsOfThunder]

Patience, a good magnifier, some fine point tweezers, small diameter solder, a steady hand, a Metcal iron with a STTC-140 tip and some more patience. This will get the job done.

Btw, I think the Weller irons would just be worthless for this job, IME (in my experience.)

HTH!
Charlie

 

[TomWaterman]

Hi Tamas,

I read a good tip, a small blob of super glue under the device will hold it in place, allowing you to solder.

However its not soo good when it comes to switching out a burnt one!

Cheers Tom

 

[owel]

There is a liquid solder you can buy at Radio Shack. You spread it from a tube (looks like model glue Revell), then heat it up with a soldering iron and it hardens.

 

[tk@halmi]

Thank You all for the tips. I will ask Fabio and see if we can do a board with the two differential pairs swapped to the CMKT5088s. There is no way to bread board with these tiny surface mount. components

Tamas

 

[SonsOfThunder]

tk,

You might be able to get a proto eval board that will fit that package and allow you to put other parts on the board. Digikey has the Surfboard series of proto PCBs for SMT, but I don't know offhand if they have one for that package.

btw, the easiest way that I know to initially attach any SMT component is this: 1) put a couple of drops of no-clean flux onto all the pads 2) pre-tin the two pads that are diagonally opposite one another 3) hold the component in place with a pair of fine tip tweezers while you "sweat-solder" the leads over the two pre-tinned pads 4) solder the remainder of the pads. This works for me.

Also btw, I once self-etched a two sided PCB with a couple of SO-16 chips and several 1206 resistors and caps. It was about 1-inch x 3-inches. It worked well, but I promised myself I wouldn't do it again. :thumb:

HTH!
Charlie

 

[PRR]

> I thought they forgot to put something in the plastic bag

People with eyes younger than mine can see and even hand-solder those things. But four of them could dance on the tip of my regular solder iron and I wouldn't see them.

So you don't need an SMT factory, but you probably need a teeny iron, a strong no-hands magnifier, and if you are much past drinking-age, a young sharp-eye kid to do it.

BTW: if you have an old 35mm SLR camera, the 50mm lens is an excellent 5X magnifier, much better color correction than a simple lens. Hold the film side toward the tiny object, about 1.5 inches away, and put your eye about 10 inches out from the face of the lens. Adjust lens to object distance to find focus. Lens to eye distance is fairly uncritical, as long as it is much more than lens to object distance. The 30mm wide-angle lens may be a stronger magnifier, but fish-eye (super wide angle) lenses may distort too much for comfort. Telephotos are useless: a 250mm lens is a 1X magnifier, and a 125mm only 2X. If you hang around serious photographers, especially small-format darkroom geeks, a short enlarger lens (like 25mm) is really good and often not worth much if the photographer has a "better" one in her collection.

But camera lenses need a third or fourth hand when soldering. (You could screw it into a hole in a thin board, and prop the board up over the object. Need to get strong light under there too.)

And camera lenses, all simple lenses, have a basic problem: the shorter the focal length, the stronger the magnification, BUT the closer it has to be to the object. So it is hard to get light or the soldering iron under a strong lens. Worse with camera lenses, because they are multi-element (but designed to work as a simple lens). The effective center-point is inside the body of the lens, so the back of a 50mm lens needs to be around 30mm from the object.

The way to get a close-up view from a distance is telescope or binoculars, a 2-lens system. Of course most telescopes are tuned to focus from Saturn to the neighbor's window, not to the workbench, and are bulky. They do make head-mount binoculars for surgeons and other fine work, but they are not cheap. (Not to be confused with the simple $19 head-mount simple-lens magnifiers.)

 

[tk@halmi]

Thanks Charlie and PRR. I have a "helping hand", I will look into upgrading the lens on that. Also I saw a head mount goggle setup with x3.3 magnification, and I wonder if that would be enough.
As PRR pointed out it does "seem" that lighting is just as important as magnification. There is a goosneck with a halogen bulb that is waiting to be mounted on my bench.

Thanks,
Tamas

 

[Bauman]

Patience, a good magnifier, some fine point tweezers, small diameter solder, a steady hand, a Metcal iron with a STTC-140 tip and some more patience.

I can buy this stuff, but I cant garantee a steady hand... :sam:
maybe more patience will be hard also.. :twisted:
:thumb:

 

[Dan Kennedy]

I'm old, almost 50, but I solder these things all the time. PRR's right in that an intense light source is good, as long as it's fairly diffuse. The halogen gooseneck thingy's have to be aimed fairly carefully to not glare.

I bought a $200 second hand stereo microscope with boom arm and heavy-ass stand. That, good tweezers, the Metcal iron or a little American Beauty, liquid flux, and not too much coffee and it's easy.

By the way, for desoldering, the old standard Ungar hot air gun does wonders.

Without the scope I can hardly see them, much less read the code numbers...

 

[Kev]

[quote author="Dan Kennedy"]I'm old, almost 50, but I solder these things all the time.
Without the scope I can hardly see them, much less read the code numbers...[/quote]

I'm right behind you Dan ... so it is nice to know that you can still see this stuff ... just ... :thumb:
At 42, I hope, I have a few years left in this yet.

 

[Flatpicker]

[quote author="Dan Kennedy"]I'm old, almost 50...[/quote]50 aint old! :wink:

 

[mesmer]

Hey Dan its very cool that you're here.cheers,
Peter

 

[PRR]

> I'm right behind you Dan ... At 42

It is a long way from 42 to Dan's 49.(*)

And a much longer way from 49 to 50....

(it's a long way, to tip a rarrie... a long way, to go....)

(*) This is especially true for eyes. A normal eye focuses at infinity when relaxed, and has to bunch-up to focus close. When young, you can usually focus to less than a foot. Over time, the eyeball-lenses get stiff, and won't bunch-up like when young and limber.

(Some good info on why eye-lenses are different from any other cells in your body in the current Scientific American.)

The normal eye is losing close-focus from age 20 or 30, but not enough for most people to notice. At 40, you notice but can live in denial. At 50, denial gets tough. Some folks deny into their 50s, and indeed good genes, good light, and just avoiding being aggravated by small objects makes a lot of difference.

But I've always been nearsighted. I've worn glasses all my life except for close-ups. While my far-vision has been stable all my life (that's pretty built-in), as years go by my bunch-up near-vision has been going away. This sucks because I used to be very good with small things. Now I am only average, and I can't handle that.

All you 40-somethings will be cursing small print soon, and in 5 to 15 years will own a set of Reading Glasses (or quit reading). If there is nothing very wrong with your far-vision, the $10 reading specs are fine (as long as they don't look like junk glass). A "2X" spec will let you read at 19 inches while your eyes work at infinity. 3X is good for 13 inches. When you are not-so-old, you can wear 2X and bunch-up to 13 inches, and pretend your eyes are not weak. But it is a strain. Somewhere around 60 you will have nearly-no bunch-up left, and have to use 2.5X and 3X reading specs (and stronger for closer work). And you will lose them and break them and generally be annoyed.

Light makes a big difference. Four times the light cuts the circle of blur in half. 60 year olds can sometimes thread needles in full sunlight, because the eye stops down to a pinhole. But typical room like is 100 to 1,000 times dimmer, the fuzz 10 to 30 times larger. It is nearly impossible to approach the intensity of sunlight indoors (the best dentists' worklights may come close). In my early 40s, I rigged 80 watts of fluorescents over my bench, and I could use more now.

 

[Kev]

It may be a long way to 50
but more and more I feel like I'm there already and it's not just the eyes ...

back, knees, shakey hands and fingers
perhaps it's not the years but the miles ... or the load ... or perhaps just the road I took.
:roll:


ooorrrggghh
is the sound my father made

It is now my sound. :wink:

 

[Dan Kennedy]

PRR, you are so right. I too have a pair of 40w flourescents about 4 feet up from the workbench.

I also have a gooseneck halogen spot lamp and gooseneck magnifier right next to the soldering iron. That's the right hand side of the bench, the microscope with it's massive base is on the left. The boom on the scope is long enough to swing out to the center of the bench. Works well.

I walk around with two pairs of glasses, I've worn specs since I was about 6 years old, so it's natural. One pair is for driving, one pair is for close work, and they both hang on my shirt collar when I'm walking around the office. The close pair are safety glasses, not stylish, but essential, as I go between soldering/desoldering, grinding, drilling or milling all day long.

Out in the metal shop I rigged up one of those 4 x 8 foot flourescent backlight panels that are used in stores to light up big advertisements. It'll hold up to 14 4ft lamps, but I just have 8 in there now. Nice and bright.

Cheaper to run then the 1000w mercury vapor or whatever it is mounted
up on the ceiling, and lights the work area better.

It does kind of suck to be blind as a bat :grin:

 

[Gus]

I have worn glasses most of my life, nearsighted. At about 35 you cannot focus on the end of your nose. The cells build up on the lens as you age and that makes it harder to focus IIRC.

I need to find the web site for the following I read in the past. People are working on hollowing out the len and finding a bio compatable fluid with the right index of refraction.

This is a cool Idea IMO instead of have a fixed plastic lens inserted you would have your lens still able to be moved by you eye muscles behind the iris

I also read something about blue light being harmful like UV rays for the eye. I did not say I believe it I just read it.

 

[SonsOfThunder]

You guys are all making me feel a lot better about my close up vision. A few years ago, maybe 4 or 5, I started having problems with dry eyes. So this causes some focusing problems. I have allergies to grass and tree pollen and take a lot of antihistamines ("...that's what wrong with Charlie!"). So I have done the eyedrops thing but not enough really. I hear there is a new prescription eyedrop that promotes the natural production of tears..."ask your doctor!" I think I will soon!

I'm 38 and have a severe astigmatism...diagnosed at 16 when I got my driver's license. That's probably why I was no good at sports as a kid...couldn't see "where" the ball was!

Gee, Dan, now we know how you keep that great tan year 'round!! :grin: :grin: :grin:

Peace!
Charlie

 

[jrmintz]

I had absolutely perfect vision until I was about 43. Since then it's been all downhill. I'm 50 now and it's starting to stabilize (I hope) at merely shitty and annoying. My eye doctor said to me, "getting old sucks, doesn't it?"

What I don't get is, aside from saving space why are those little tiny components an improvement?

:thumb: