Soldering Surface Mount Components - Suggestions? How to??

[Mike/W8BAC]

Typing this on a phone and for.some reason I.can't see the box so im not sure what the hell im typing haha

I have that trouble when I'm driving and posting.    I'm installing a 27" monitor on the dashboard so I can see what I'm texting.

I'm going to order one of the video microscopes and give it a try. I can think of a few other uses for it and the price is right. If I have time before the next job I might post some pictures here.

In this Youtube video http://www.youtube.com/watch?v=7kyaz4Zrd78 (posted earlier) the guy obviously is selling a kit of paste flux and low temperature melt solder? I would like to find out what kind of solder he is using. Can anybody point me in the right direction?

The solder he uses is hard and thick but the benefit of keeping the regular solder molten longer so the part can be removed would be a big help on other projects as well. Thanks.

Mike

[gerry_w1id]

I work for a semiconductor company and we solder surface mount components every day. If I convert .5mm to English that translates to almost 20 mils? Gee, that's a lot more than the 5.5 mils we regularly "play" with. I think in mils because that's what we use in-house even though we are a well-established international semiconductor company. Our spec sheets use both measurement systems. While there will be myriad expert opinions offered, the ones by W1ATR are very similar to what I would suggest. If you are new to SMT, then I honestly think you may be a little late in the game to start with this particular project you have in mind. You might try "warming up" so to speak on a smaller, less complicated project. On thing to remember is that virtually all the components offered for sale today are ROHS certified. That is to say, meant for use with lead-free solder. There will be those who lament the politics involved, the world is going to hell in a handbasket, etc...etc. This is nevertheless a fact that has to be reckoned with and it can be easily addressed: pre-tin the part with lead solder. Otherwise the quality of the solder connection, particularly if the solder pads are small, will be at best tenuous. Cleaning the board and IC before starting will also address another troublesome variable. You need to start with clean surfaces to help ensure good solder connections.

[W1ATR]

Here's a juicy little tidbit for the hive. If anyone is interested in the chipquick method, the alloy wire they use, then same alloy that is approx $100 for 8ft, is whats called Cerrolow-136. It's been around for ages in the milling and casting industry, and I think it's only been in recent years that someone figured out it's eutectic and mixes well with electronics type solder. It lowers it's melting point so low that after heating, it stays liquidy (<is that a word?  ) and workable for a pretty long time.

A buddy of mine brought me home a small block of it years ago from the mill where he worked and I used to carve off short slivers and use it while playing around under boatanchors. You know how annoying point to point wiring can be when you have to take something out and theres 4-5 wires and leads all twisted up thru a single eye connection on a tube socket or wiring bridge. Id flux the connection, heat it, and feed in some of this stuff, then suck away all the solder from the connection. the true beauty was that the remaining slobber would stay molten for like 30-45 seconds so I would have loads of time to unravel the mess from the eye to get to the part I wanted.

I lost that little block a long time ago   then just got lazy after that and go in with the dikes and cut away everything haha.

Googled up an MSDS below. Maybe someone knows a source for wire.

http://www.chemcas.com/msds112/cas/2834/7440-69-9_7439-92-1_7440-31-5_7440-74-6.asp  

[gerry_w1id]

I hate it when a solder connection goes round and round and when she stops nobody knows. That was when it was thought solder could not be used to secure a connection. You had to wrap wire securely around a terninal and then solder. Then solder got better and they got smarter. A serious problem we sometimes encounter is trying to unsolder a SMT chip from a multi-layer PCB with some of the layers being 2 ounces. 1 ounce copper is more common but 2 ounce copper is used when you're carrying a lot of power. For the curious, 1 ounce copper is 0.00135 inch thick and 2 ounce copper is twice that. Really sucks up whatever heat you put on the part and it takes a very long time to remove. It's especially horrendous when the solder that was originally applied is lead-free because lead-free solder has a higher melting temperature. I end up using 2 hot air guns, one on top and one on the bottom while the board is held in a clamp. When I see solder melting, I grab the part with a pair of tweezers. It's not getting any easier.

[steve_qix]

Thanks for all of these good suggestions!  I'm still working on the PIC software at the moment using a development board (it has the parts already mounted).  However, soon I'm going to have to mount a PIC on my own board, and this is where the surface mount soldering is going to be necessary.

I'll report back when I do some actual soldering!

Thanks and Regards,

Steve

[Mike/W8BAC]

I picked up an HD video, USB, microscope and have been testing it out. I pulled out a board from a 1987 Compaq (286) laptop computer and took a few stills to show the scopes ability.

The first shot shows a row of small objects. The top brown component (a cap I think) measures .058" square X .120" long. The two black components (marked 470 and 330) I believe are resistors and measure .030" square X .060" long. The object in the foreground (out of focus) is .060" by .135".

The second shot is an electrolytic cap. At .175" square X .250" long they are the largest components on the board not counting the microprocessors. I didn't catch this problem with my magnifying visor. I checked the cap with an HP 4261A and an ohm meter. It's shorted and possibly the reason this board failed.

Both shots are 1280 X 1024 resolution and about 1MB if saved as JPEG's. The second shot was saved as a bit map image and converted to JPEG for viewing here on the BBS. The scope was just a fraction of an inch from the board for these shots but the scope will work at 4-6 inches from the work by adding more light. You can view your work in real time @ 1280 X 1024 full screen and take a snapshot any time by pressing the button on the LED light control located on the USB cord.

I like to sharpen knives and think I do a descent job. I use a visor often to make sure the edge is consistent. I took a look with the scope and can see I need more practice.

[kg8lb]

 Hey Mike,
  The micro shots are pretty cool ! We do quite a bit of micro surface mount stuff here at work using the binoc visor  (30 years ago would have been easily done with the naked eyes !) The USB scope really make for a sweet look at the final product. If not used for the actual intitial work it would still be a great inspection tool.

  A note on the "Cerro" alloys: There are many different Cerro products in use. We used them a a filler for moldings and tubular parts in metal fabrication for many years. The Cerro products were pretty much made history  here due to the fact many of the alloys contain substantial percentages of Cadmium. Just adding this a a caution. Know what you are working with and the safest handling practices !

[WBear2GCR]

One thing to consider with the micro optics is "depth of field"...

                      _-_-bear