Soldering and Desoldering Surface Mount Components

Intro: Soldering and Desoldering Surface Mount Components

These instructions will help you familiarize yourself with the initial difficulty of soldering surface mount components. By the time you have finished, you will be able to solder components with pins with .5mm spacing.


Tools and Supplies

1. x1 soldering iron (digital or analog)
2. PCB(Printed Circuit Board) with available pads
3. SMD (Surface Mount Device) component that matches the available pad
4. Solder (recommend water soluble, rosin core acceptable)
5. Desoldering braid
6. Flux w/ applicator
7. Tweezers
8. Rubbing alcohol (rosin core solder) OR
9. Water (for water soluble solder)
10. Anti-static cloth

STEP 1: Preparing the PCB

1. Check to be sure the pad size of the PCB lines up with the pins on the SMD

2. Clean the PCB of any dust or debris.

3. Turn the soldering iron on now, and set the temperature between 600-700 degrees.

Warning: When heated to these temperatures, you will be burned if you touch the tip of the soldering iron.

STEP 2: Use Tweezers to Position the Component

Align the pins of the component with the pads on the circuit board. Since most surface mount components have the same amount of pins on both sides, it is important to find "pin 1" every time you place a new component.

STEP 3: Tack Down One Corner

1. Keep one hand still, holding the component in place with the tweezers.

2. By now, the soldering iron should be hot. Get a small to medium sized dot of solder on the tip.

3. Pick any corner pin on the component

4 . Touch and hold the soldering iron to the pad that will be associated with that pin.

5. If you have done this correctly, the solder should have transferred from the pad on the circuit board to the component pin, it does not matter if you have connected excess pins, this will be fixed later.

STEP 4: Flux

There are 2 purposes for flux in soldering: to prevent beading of the solder, and help the solder flow from the soldering iron to the circuit board. Flux will be used on this board to limit the amount of bridged connections made, and generally make the job easier.

1. This substance is messy, so be sure to use an applicator. (toothpick, brush, etc.) In this case, I have used a metal tip.

2. Get a large amount of flux on the applicator.

3. Spread the flux over the pins on the opposite side of the component that was tacked down in the previous step.

STEP 5: Solder

1. Pick up the soldering iron in one hand, and the solder in the other, as per the picture below.

2. Use the soldering iron to heat up the pad, not the pin on the component.

3. While the pin is hot, position the solder between the pad and the pin. The heat will melt the solder, and the flux will cause it to flow where it needs to.

4. Repeat this as many times as necessary.

STEP 6: Heat Up Desoldering Wick to Fix Tack

It is fairly common that while preforming the previous step, a solder bridge will develop. A solder bridge might look something like the picture below.

These steps will also work for removing the component from the board.

1. Take the desoldering wick and place it over the solder you want to remove.

2. With the soldering iron, lightly press on the wick, to ensure the heat is transferred through to the solder.

Warning: Remember that heat removes solder, not pressure. Too much pressure applied could remove the pad or pin on the component, ruining the component or board.

STEP 7: Solder

Now that the solder has been removed, repeat step 5 for this side of the board.

STEP 8: Fix Any Remaining Solder Bridges

Use the method described in the previous steps to remove any more bridges.

STEP 9: Clean With Rubbing Alcohol

If water soluble solder was used, replace rubbing alcohol with water.

1. Take the anti-static cloth and pour a small amount of rubbing alcohol onto it.

2. Gently clean around the newly soldered component, and where any excess flux exists. This will give a more professional look.

STEP 10: Conclusion

Congratulations! You have now finished soldering your first surface mount component.

Comments

[MacStevins]

And how to desolder a smd components?

[HBSkirmit]

In step 5 second sentence, you say " Use the soldering iron to heat up the pad, not the pin on the component.". In the next sentence you say "While the pin is hot, position the solder between the pad and the pin". How did you get the pin hot when you didn't touch it ? Did you mean to say "pad" ?

[JG92]

The pin should heat up sufficiently from the heat being transferred from the 'pad' with the help of the flux. The reason you don't want to touch the pin itself at this point is because you will certainly push the component off of the traces. Once you have this first pin tacked it is easier to solder the rest of the pins without misaligning the IC.

[JG92]

I don't know, if you have to be told to "pick up the soldering iron in one hand, and the solder in the other" then you may not be ready to try soldering surface mounted components, but if so, then here are a few clarifications. In step 2 you are told you need to find pin 1 but not really how. On most IC's there will be one corner of the case that is cut out. If you look close at the image you can see it on that IC. The corresponding pin on that corner is pin 1. But usually there is also an outline on the PCB showing the placement, which can also be seen. Just put the cut out corner where shown on the PCB. In some instances there is a dot on the IC case marking pin 1. That dot is the same as the cut out corner.

[d1ndian]

A much better method form future -----> take a tin/aluminum tray ,turn the victim circuit board upside down and place it on tray, use a heatgun to heat the board, do it at intervals so that the board or components don't get too hot, carefully use anything to tap on the board and the all components will fall in eventually. Be carefully while tapping coz solder behaves like water droplets.

[jam BD]

Very nicely detailed :D
I didn't think flux was conductive...