Changing SMD parts

[Goodrat]

I notice people are a little skirmish about changing SMD parts, so this is what I do:

Use a good soldering iron. Variable is preferable and I set mine to around 600 deg F.
Get a nice pair of tweezers.
Melt a small amount of solder on one side of the installed part, then the other side and repeat until both sides are molten and slide the part away.
Use solder wick and remove solder from both pads.
Add a little fresh solder to one pad.
Position the part and while placing with tweezers, melt the solder you have on the one pad, and possibly pushing down slightly on the part.
If you are happy with the placement, solder the other pad. Use little solder and make sure it flows nice.

I think that is way easier than a leaded part.
With an IC, same process. Remove with plenty of solder, clean up the pads, solder one pad, melt and place, solder the other pins.

[R O Tiree]

Top tip - add some flux before you start melting solder to remove the component.

[AdamM]

You could buy another soldering iron too!

[Mark Hammer]

Use plastic tweezers if you have any suitable.  Tiny resistors may stick to metal ones.  Alternatively, place the resistor in position with the metal tweezers, then hold it in place with a toothpick, which ISN'T magnetic.

[merlinb]

You could buy another soldering iron too!

+1  It's a lot easier if you hold one iron in each hand and use the irons as tweezers!

[pickdropper]

For smaller Passives, I often just put more solder on the tip and put the iron on the long side of the component , heating up both pads at the same time.  When the solder starts to reflow, I sweep the iron the the side , removing the component.

This obviously won't work for ICs.  For those, a heat gun is usually effective.

[Goodrat]

I never liked using flux. Too messy.
What I do is add solder that has flux in it and then use the solder wick, sometimes I start the wick flow with a touch of solder.

[pickdropper]

I've met other folks that dislike flux as well.  For me , it is indispensable for SMT work.  It is indeed messy, but I wash my boards with flux remover at the end and that cleans them up nicely.

[Ice-9]

Flux is your friend, I use the mini-flux no-clean flux. there is no residue, couldn't live without it in the world of SMD, it makes reflowing large IC's a doddle  

[Govmnt_Lacky]

The problem I run into is the lifting of the pads. When removing an SMT resistor, How do you get BOTH ends to heat up in order to pull the resistor?

I can heat them up 1 at a time but, how can you get BOTH sides molten in order to pull up the resistor without lifting the opposite pad 

[Ice-9]

The problem I run into is the lifting of the pads. When removing an SMT resistor, How do you get BOTH ends to heat up in order to pull the resistor?

I can heat them up 1 at a time but, how can you get BOTH sides molten in order to pull up the resistor without lifting the opposite pad 

If you just use a soldering iron then it can be simple to heat one side of the component then slide the iron to the other side, if done quick enough then s you heat the second side the first is still liquid and the component just pushed straight off without and damage to part or trace. It can take a little practice and sometimes you have to slide the iron from side to side to keep the joints from going solid.

The best way is a cheap gas hot air iron as this will heat both side at the same time and the component will just lift off or with those little irons that look like tweezers to heat and lift in one motion.

[pickdropper]

The problem I run into is the lifting of the pads. When removing an SMT resistor, How do you get BOTH ends to heat up in order to pull the resistor?

I can heat them up 1 at a time but, how can you get BOTH sides molten in order to pull up the resistor without lifting the opposite pad 

If you just use a soldering iron then it can be simple to heat one side of the component then slide the iron to the other side, if done quick enough then s you heat the second side the first is still liquid and the component just pushed straight off without and damage to part or trace. It can take a little practice and sometimes you have to slide the iron from side to side to keep the joints from going solid.

The best way is a cheap gas hot air iron as this will heat both side at the same time and the component will just lift off or with those little irons that look like tweezers to heat and lift in one motion.

I was never very good at heating one side then the other.  I just swipe on the long edge of the component and heat both pads at the same time.  Perpendicular to how you would normally solder the part.

[R.G.]

+1  It's a lot easier if you hold one iron in each hand and use the irons as tweezers!

Although I did once get compliments on my chopsticks technique in Japan, I think that these would be easier than two irons:
http://www.mcmelectronics.com/product/21-8230

I have a set, and use them all the time. The accessory tips will also melt all the leads of a DIP at once too. That's probably worth the price, and you don't even have to admit to using SMD parts.

[Goodrat]

I always add fresh solder to both sides to get things flowing and hot, then moving side to side however many times it takes, probably 3 or 4.
Enough time to get the solder very hot, but quick enough to heat the other side before the other cools.
With a slight push to one side while you are doing this, the part will slide. Just swipe the part away with the iron. I've taken off 14 pin IC's that way.
Yeah, have a light touch around small pads. Damage risks will depend on board quality.

[Govmnt_Lacky]

I've taken off 14 pin IC's that way.

How are you keeping ALL 14 pins of the IC molten to "swipe it out of the way?" 

[pickdropper]

+1  It's a lot easier if you hold one iron in each hand and use the irons as tweezers!

Although I did once get compliments on my chopsticks technique in Japan, I think that these would be easier than two irons:
http://www.mcmelectronics.com/product/21-8230

I have a set, and use them all the time. The accessory tips will also melt all the leads of a DIP at once too. That's probably worth the price, and you don't even have to admit to using SMD parts.

Yeah, I finally sprung for a Metcal/OKI tweezer station earlier this year.  A bit expensive, but very handy.  As you said, it is useful for through-hole stuff as well as SMT.  The range of tips is cool as well, from ultra-fine tips to the spade type tips that for dr soldering ICs.  I can only do 8 pin PDIPs, however.  The wider tips are pricey, so I'm holding off on them for now.

[lespos]

For me best way soldering SMD components is solder paste and heatgun (must be with adjustable speed and heat).

Solder paste


PCB


With tooth stick add a small drops of solder paste to pads. It's ok, if now it looks a bit messy. After heating everything will be as it should be.


Put the necessary components



Set the heat gun on slowest speed and about 250-300 celsius degrees


...and that's it! Clean and tidy.


If you need change some SMD components, it doesn't matter - resistors, capacitors or IC's with 100 pins - use heat gun. This is the best way! All you need is a little bit practice and patience

[Govmnt_Lacky]

I LOVE the solder paste/heat gun method! Especially when I already have a good Stinel heat gun to use 

Is there any caution needed to stop from damaging components with the heat? Can SMT IC chips be over cooked? 

[lespos]

I LOVE the solder paste/heat gun method! Especially when I already have a good Stinel heat gun to use 

Is there any caution needed to stop from damaging components with the heat? Can SMT IC chips be over cooked? 

No worries. By overheating you can damage PCB rather than IC's. Of course, after using heat gun, you must cool down IC and whole PCB before power it up.

[pickdropper]

Anything can be overcooked, but the parts are usually a bit more robust than one would guess.