Sneezed, and the part dissapeared!

[jkrienert]

First post, so bear with me.  
I must say before I throw in my question, there are so many brilliant minds here who are willing to share their wisdom unbound.  Infinite thanks!

To the point:
  After loaning my beloved 30watt to a friend, I was left to be resourceful and chose one of the many micro-amps online, and do a small build.  
  Excitement lead me to accidentally burning the only LM386 I have thanks to my novice electronics experience (an improperly sized resistor... oh the whoa of being color-blind).

  While sourcing new parts, starting from scratch, and thoroughly relearning, I got hung up on a link to a pdf describing a IC with many like characteristics to the LM386.  The LM-4951.
  I went ahead and ordered 5, as opportunity allowed me to only cover shipping fees. I thought this chip would be an ideal size for the application, and its heart basically beats on the same configuration as the LM386 with lower power draw.
  Man, this thing is waaaaaaay smaller then I expected (not necessarily a bad thing for a 'micro' amp).   I am amazed it can drive 8ohms/1w!

  Now that I have described my situation, I wanted to ask anybody who has experience with small ICs, and could possibly help me through the process of either:
           -making a small board cheaply (which I have never done, but would love to learn)
           -or help me abide to my original plan of somehow of doing point to point (if its even possible with a chip like this?!)
           -another alternative might be that someone produces a 'cradle' for this chip, making is much easier to solder?

  Along with the photo, here is the link for the data sheet on this chip (save ya some search time).
        http://www.national.com/ds/LM/LM4951.pdf

   

  If someone pulls through and helps me, I will gladly ship you a couple (2) to test and build with for your troubles!

Alright, I sure hope that was clear enough. Thanks.

-jmk-

[jkokura]

We have the same initials.

It looks to me like you got an SMD part when you were expecting to get a normal PDIP part.

My first reaction recommendation would be for you to get the LM386 your amp should have rather than try and use the SMD part.

Jacob

[Taylor]

It's possible to use that chip. It's even possible to use that chip in a point to point build. But I would strongly recommend you don't bother, assuming that you have not done anything like this before.

The 386 is a cheap, readily available part. Unless you really enjoy a challenge, I don't see any reason to use that chip instead of just buying a 386.

I build stuff using surface mount chips every day. But even I wouldn't bother with that kind of package.

[jkrienert]

I realize the price of the part is cheap, but whats mainly keeping me on this route, is I have 3 (considering I give two to someone who wants them, or can help me).
The three chips I have (if I can get them to work) would be simply added in 3 enclosures ready made... essentially I have three and three, and am a bit determined to make em work.

I do plan on getting a 386 in the future.. but I guess adversity just makes me more motivated... personality flaw I suppose.

I wonder if I could solder rails on it and make it like a DIY DIP chip... any thoughts on this?

[phector2004]

a better idea would be to look at adaptors. Don't know if they come in that variety, but they seem very easy to use. Just place carefully, heat grooves, and the board solders in place

[jkrienert]

Doh!
I just did a search for SMD to DIP, and first thing that comes up...

Is this what you were mentioning 'phector' ?

http://www.instructables.com/id/Make-SMD-to-DIP-adapters/step2/Make-the-board/

although I kinda kind the instructions a bit hard to follow being a noob.

[phector2004]

http://www.futurlec.com/SMD_Adapters.shtml

Only place I've seen them on sale so far...

Seem great for designing compact chip amps, but haven't tried them out yet. Youtube has some instruction videos on how to use them.

Best of luck!

[Taylor]

Soldering that kind of chip onto an adaptor is going to be just about impossible, because the pads are under the chip's body instead of having pins that stick out like all the chips in that link. The chips in the link are SOIC, but yours is an "SD" package which has no pins.

The only way to do this that I can think of is "dead-bug" style: place the chip on its back, glue it down to the board, and solder parts directly to the pads. I've done this, and again I don't think it's worth it, but it sounds like you're looking for a challenge, so that's fine with me.

[jkrienert]

*laughing*

dead bug? wow. As funny as that hit me, it actually seems like a good idea. 
In stances when you have done such, is there heat special glue, or need for a small salvaged heat-sink as the base?

so if I was to mummify this bug as such and solder the leads point-2-point style, could I encase a small amount of the contacts in a drop of epoxy, or is that going to screw up continuity?

jmk

[jkrienert]

phector, where did u you find the u-tube clips on SD cards?  I'm having trouble finding any. :S

[phector2004]

phector, where did u you find the u-tube clips on SD cards?  I'm having trouble finding any. :S

Leaded parts: http://www.youtube.com/watch?v=vZ1qisX52rI&feature=related
Adapter: http://www.youtube.com/watch?v=E6WrzdgwyIw&feature=related

I don't know about SD components, but Taylor's experiences with them don't seem too promising and he's got a ton more knowledge about this stuff than I do. You can try to solder it onto a board, maybe the solder will bridge the space between the pads and the board traces, but these components are generally handled by robots!

[jkrienert]

well... I am no robot, but I do have sharp vision and steady spidery fingers.  I suppose since I have 3, I will test two methods... a cradle-board, and a "dead bug" style.

Phasor and Taylor, would you like one each of my spares for sake of the instant responses? (honestly didn't expect anyone to post anything let alone in the hour after the question originated)

[jkrienert]

after watching those videos... I am leaning towards the pre-made board method.. seems like it would be the best option in preventing shorts.

are any on this page applicable (only a few 10pin ones)?  
http://www.ezprototypes.com/DipAdaptersMain.php

or... Would anyone know a good route to begin learning how to make a simple SD pcb board from scratch?

  (you might be thinking, why doesn't he just by a lm386?! It would be cheaper, and faster!)  True, but in defense... I have intensest in learning about small form chips, and making boards from the beginning, as I never have.

jmk

[jasperoosthoek]

I have point to point soldered such a chip. They worked but the connections kept breaking. Then I overheated one with the heat from my soldering iron. That route is a dead end to me.

Last thirsday I did my first experiments with solder paste. I first read about that on this forum a few weeks ago. It is basically solder flux which was grinded to a powder with some liquid flux. I experimented with soldering a gold coated glass cylinder on a so called chip carier. I just heated the carries above the tin/lead melting temperature and it was fixed.

The chip carriers I use are like DIP chips but without the chip. You can mount a chip like yours on top with some paste and heat it. I have them at work so I do not know if the pattern matches...

Of the one type I can use as many as I want because they were used in a different way. If the pattern of my carrier matches your chip then I would be glad to solder a couple of them. That gives me some more experience which is what I would get back from it.

I'll have a look on monday.

Jasper

[earthtonesaudio]

The large central pad on the IC is for connecting to a heatsink.  So whatever you decide to do, that pad needs to connect via a short, low thermal resistance path to a heatsink with an area of at least 1" square.  If you do it dead bug style, I would suggest mounting the IC upside down on a piece of 1oz (or thicker) copper clad, and using a solder-saturated length of desoldering braid to "bridge" over the IC.  Solder each end of the braid to the copper clad and the middle to the IC.  The distance between solder points should be as short as possible.

From there, you're basically building on top of a heatsink.  Note that the remaining pads are quite small (0.12mm²!), so 1/4W resistor leads may be to large to mount directly.  1/8W may work, but I would suggest getting some "wire-wrap" wire (about 30awg) and using it as hook-up wire from component to chip.  Mounting the other components to the copper clad board will require insulating them from the copper somehow, and at this point it becomes even more practical to simply etch some form of circuit board.  Take a look at the datasheet's suggested layout.  They run an array of vias from the central pad, through the PCB, and to a heatsink on the other side that takes up almost the entire area.  That's a good model to use.



...That said, I think you should just order the LM386 as a DIP and save yourself the frustration.

[jkrienert]

Ok ok.  Advice is setting in.  I am going to order a LM386 and set that as the intended heart of the amp.

YET!  Until the package arrives, I am going to have a go at the dead bug style as mentioned by earthonesaudio and Taylor.  Figure practice and experimenting is what this stuff is all about!


Thanks so far!

[deadastronaut]

lm386n-4 ...you can squeeze 2watts out of it....

or lm380n.....2.5 watts too.....

check the data sheets...

[jkrienert]

dude. You guys are right.  the 386n-4 is the way to go, and i just swooped a couple up.

in the mean time, I went through with the dead bug mounting, and will post a photo in a little while to see your thoughts.
ridiculous... I cut and hammered out a 3/4" copper coupling, and cut a sliver from the side.
with the sliver I made a long armed omega shape and soldered the IC inside it upside down.
then coated the arms with solder, and mounted it to the back plate.
that probably sounds like rubish, but maybe the photo will be clearer.

Im waiting for a blob of plaster to dry around the mounts so that the somewhat flimsy connections will be much more sound. Thermally the plaster is ideal... but will it work

anybody want a lm4951 no charge?

[jkokura]

Glad you came to your senses!

Jacob

[jkrienert]

wow. no takers on the free-bee chip.

I really must have made a mistake ordering em.

thanks for the help you guys.
You'll likely see an upcoming new topic disusing my amp, but seeing how many of them come or go, I am debating not bothering anyone on here with the 'same old same old...'

jmk