Soldering SMD, please help!

[mindctrl]

Hi!

OK, I just got some SMD components, and I was wondering if somebody could tell me how to solder them. Since the pins/leads are so small/nonexistant, how am I supposed to connect them to a PCB? I'm very curious about this, because it would really help minimize my circuits! Thanks for the help.

--mindctrl

 

[Juglenaut]

Heat pencil and solder paste, and holding them down with a very small amount of adhesive.

 

[Nigel Goodwin]

Or just a fine pointed soldering iron and thin solder, and liquid flux is VERY helpful for SM IC's.

 

[Oznog]

Zephyrtronics SMD paste work well. Adhesive is not strictly necessary, and prevents self-centering.
You need 2 steps. First take it to 350F for 60 sec which causes the flux to flow out of the paste, then heat it as fast and briefly as possible to flow the solder in the paste.

A butane Weller Portasol with the heat blower tip is a great hot air pencil for $20 on eBay. Some also report good results with a toaster oven.

When done properly, the part will self-center on the pads and it won't bridge the pins as long as you don't go overboard with the paste. Much less technique required than trying to use a soldering iron and far more reliable.

 

[John Sorensen]

What size components and packages are you using? I use 1206, TQFP, SOIC with no problem hand soldering with a fine tip iron and a pair of tweezers. I've also done TSOP but that's a little harder. It is helpful to not worry about bridges while you solder, but take some desolder braid when you're done and clean up all the bridges and excess.

Now that I've become proficient with SMT, I don't use through hole for any of my prototypes anymore. Performance is much better, less RFI/EMI emissions and susceptibility, and smaller and more robust boards. You're on the right track! Good Luck!

j.

 

[Dean Huster]

Pace, Inc., the soldering gurus, tell you to not use a traditional iron as it asymmetrically stresses the component and board and can cause failures later as the part remains under stress after each side cools independently of the other. I say, for hobby purposes, whatever works, works.

I've had success with paste and an Ungar heat gun with its accessory baffle that directs the air in a 3/16" stream. In fact, I use the Ungar heat gun to depopulate SMD boards for parts. Just be sure to harvest more delicate items such as LEDs, transistors, diodes, electrolytic caps and ICs first. The ceramic caps and resistors can wait until last.

If you don't have solder paste, you can always tin the board pads and the ends of the component first, lay it down and reflow the solder using the heat gun. If a part wants to wander, use an awl to hold it in place.

Dean

 

[mindctrl]

Hi guys, thanks for the great advice. I just have a few questions.

First, I sampled the MAXIM2606 VCO oscillator chip. It runs the FM freqs and I was going to use it as a super low power short range FM transmitter, but then I got the sample in the mail. It is TINY. It's in a SOT23 package, so the whole soldering idea looks pretty complicated. I don't think this oscillator comes in any other package, so if anybody has a recommendation for a bigger FM transmitter chip, I'm all ears.

Also, where do you guys buy your solder paste? I couldn't find any at radio shack. I also need to get a heat gun. I don't have a toaster oven, so I figure I could probably just use a good heat gun. Let me know! Thanks again.

--mindctrl

 

[mindctrl]

P.S., the datasheet for the VCO MAXIM2606 is at https://www.electro-tech-online.com/custompdfs/2005/01/MAX2605-MAX2609.pdf

 

[Nigel Goodwin]

Pace, Inc., the soldering gurus, tell you to not use a traditional iron as it asymmetrically stresses the component and board and can cause failures later as the part remains under stress after each side cools independently of the other.

Interesting quote, as Pace supply soldering bits to do just that as part of their soldering stations!.

 

[pittuck]

my 'technique' is to tin the pads and then place component on and then heat with iron w/ fine tip.

With ICs i solder 2 far corners to hold it down then solder the rest, i cant see how much stress can occur really!

If needs be i add more solder to a joint, but that can get a tad messy... lol.

 

[Nigel Goodwin]

my 'technique' is to tin the pads and then place component on and then heat with iron w/ fine tip.

With ICs i solder 2 far corners to hold it down then solder the rest, i cant see how much stress can occur really!

If needs be i add more solder to a joint, but that can get a tad messy... lol.

The Pace method uses a special hollowed bit, you tack the chip down at each corner, then cover the pins with liquid flux. You then drag the hollowed bit (pre-loaded with solder) across the pins - the liquid flux makes the solder flow on the pins and traks, and prevents shorts between pins.

This obviously take place one side at a time, which was why the Pace comment surprised me?.