I recently did my first smd soldering using reflow oven. It turned out to be much greater than my expectation. However, I still have two quick questions:
You have a board that already have some soldered components on it, done by reflow method. Now you want to solder another component on this board using reflow oven. Will, the process of soldering of this new component, not mess up the soldered components connection? I mean that whatever component is already there, their solder get melted again. What is your opionon on this?
My reflow oven solders both side of the board, the document says.Let’s say you have a board. This board has some components soldered on top side. Now you want to solder some components on the bottom side. What will happen? When the solder get melted, will the top component not fall? I hope I am clear.
First you can reflow a board with parts already mounted. It is not advisable to do so multiple times. Every time you heat solder it oxidizes unless you are using a nitrogen reflow oven (the nitrogen prevents oxidization …because no oxygen). If you try and reflow too many times the oxidized solder may cause problems.
If you want to dual side a board (components on both sides) it is very advisable to have different solders for each side. One solder will melt at a higher temperature than the other. You would use the high temp the first time, then mount your parts with the lower temp solder and reflow with the lower temp profile. You reflow oven must be up to the challenge as well. The different temperatures are usually not far apart.
It is possible to dual side a board with the same solder. This depends on the components that will be on the bottom during the second reflow. If the parts are small and the amount of solder is correct, the surface tension of the melted solder will hold them in place. This is a very hard thing to do. If there is any movement of the oven or board (vibration, air, warping) the parts will start falling off the bottom. I do not advise this approach.
This is why having components mounted on both sides of a board is so expensive. The board must take the same path twice. Twice in the pick and place (chip placement machine) and twice in the reflow oven.
Interesting question - for home reflowing, are there any commonly available adhesives you could use that would keep the bottom side components firmly stuck to the board at 260 celcius?
propellanttech:
It is possible to dual side a board with the same solder. This depends on the components that will be on the bottom during the second reflow. If the parts are small and the amount of solder is correct, the surface tension of the melted solder will hold them in place. This is a very hard thing to do. If there is any movement of the oven or board (vibration, air, warping) the parts will start falling off the bottom. I do not advise this approach.
I have done this a couple times (and know somebody who does it frequently) and have had no problems whatsoever. You just do one side at a time, and give the board enough time to cool. I haven’t tried it with large power components - but with ICs and discretes it has never failed me.
NleahciM:
I have done this a couple times (and know somebody who does it frequently) and have had no problems whatsoever. You just do one side at a time, and give the board enough time to cool. I haven’t tried it with large power components - but with ICs and discretes it has never failed me.
Can I ask what type of reflow oven (or other device) are you (or your associate) using.
Some convection reflow ovens circulate air which may cause parts to fall from the bottom of the board.
NleahciM:
I have done this a couple times (and know somebody who does it frequently) and have had no problems whatsoever. You just do one side at a time, and give the board enough time to cool. I haven’t tried it with large power components - but with ICs and discretes it has never failed me.
Can I ask what type of reflow oven (or other device) are you (or your associate) using.
Some convection reflow ovens circulate air which may cause parts to fall from the bottom of the board.
James L
Both of us used a cheap toaster oven from Amazon.com.
propellanttech:
The reason I say this: Never assume someone is using the same equipment as you.
I have a convection conveyor oven, and it would be almost impossible to mount components on both sides.
I also have a batch oven, but it to circulates air, and may cause problems.
I don’t doubt it could be done, but I’m not sure it could be done repeatably and consistently with the equipment like I own.
If someone is using a batch oven that doesn’t circulate the air, they are much more likely to succeed.
James L
Toaster ovens don't circulate air, as far as I know at least. My friend who uses this technique runs a website similar to SFE (though smaller) and has made hundreds if not thousands of boards with the same toaster oven.
But yeah, if your oven aggressively pushes air around, I wouldn’t be surprised if you had problems.