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Step 6Surface mounting components onto a circuit board
Soldering components onto a circuit board when the leads can be pushed through holes in the board is the easier of the two methods of soldering small components onto boards. Many circuit components need to be surface mounted on circuit boards, which forces you to be a little more precise then when you can work on the bottom side of the board.
To solder something onto the surface of a circuit requires a process called tinning. Tinning is when you apply a small amount of solder onto the materials you are joining before you connect them. In this case, it involves putting some solder on a contact on the surface of the circuit board then attaching the component to the solder pool. Mitch showed me how this process is done.
First he touched the tip of the iron onto the small pad on the top of the circuit board. He then introduced a small amount of solder onto the pad and took the iron away.
Then, a few seconds later he picked up the component he wanted to solder with a set of tweezers, heated up the small glob of solder that he had just placed down, and gently lowered the contact on the component into the pool of hot solder.
He took the iron away, held the component in place a few seconds longer, and released the component from the tweezers.
He then went to the other side of the component and finished making the connection by soldering the remaining two contacts together.
Surface soldering is done like this because you need to lower the component into place by hand, so it's hard to hold the iron, the tweezer and the solder all at the same time. Additionally, tinning is just a good thing to do while soldering small components. I didn't tin the wires before I soldered them because they were so big I was sure I was going to be apply enough solder to make a good connection. However, when soldering small components or doing surface mount soldering like this, tinning can be really helpful because you basically already have your solder applied to your pieces before you go to connect them. There is no need to glob on more solder and run the risk of getting it in a place where you don't want it to be.
The picture series below shows the process unfolding step-by-step.
To solder something onto the surface of a circuit requires a process called tinning. Tinning is when you apply a small amount of solder onto the materials you are joining before you connect them. In this case, it involves putting some solder on a contact on the surface of the circuit board then attaching the component to the solder pool. Mitch showed me how this process is done.
First he touched the tip of the iron onto the small pad on the top of the circuit board. He then introduced a small amount of solder onto the pad and took the iron away.
Then, a few seconds later he picked up the component he wanted to solder with a set of tweezers, heated up the small glob of solder that he had just placed down, and gently lowered the contact on the component into the pool of hot solder.
He took the iron away, held the component in place a few seconds longer, and released the component from the tweezers.
He then went to the other side of the component and finished making the connection by soldering the remaining two contacts together.
Surface soldering is done like this because you need to lower the component into place by hand, so it's hard to hold the iron, the tweezer and the solder all at the same time. Additionally, tinning is just a good thing to do while soldering small components. I didn't tin the wires before I soldered them because they were so big I was sure I was going to be apply enough solder to make a good connection. However, when soldering small components or doing surface mount soldering like this, tinning can be really helpful because you basically already have your solder applied to your pieces before you go to connect them. There is no need to glob on more solder and run the risk of getting it in a place where you don't want it to be.
The picture series below shows the process unfolding step-by-step.
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Great instructable!
I generaly don't tin the contact because that tends to make it more difficult to get the component to sit flat on the board. Generally, a commercially produced board will have enough tinning on it to make the component stay in place until you can finish the joints.
Step 1 is to apply a small amount of rosin flux to the pads that the component is going to be soldered to (I have a small bottle with a brush in it)
Step 2 is to place the component using tweezers (As per the second pic), and WHILE HOLDING IT, touch one of the pads with the iron. If you have a clean, recently tinned soldering iron tip, the small amount of solder on the tip will wick into the joint and hold the component in place (once it cools)
Step 3 is to check that the component has stuck, then solder the OTHER pads before finishing the first one off. Try not to get too much solder on the joint. You're after nice smooth meniscuses rather than big blobs.
If you're solering onto a board that you have made yourself, tin the pads then remove excess solder with solder wick before doing step 1.
You use liquid flux in conjunction with flux-cored solder. Just a little extra flux in the right places makes the work go much more smoothly.