Hi folks,

I just got my AVRISP mkII kit in the mail. It comes with the PCB (very neat design) and all the components, one pre-programmed ATmega8 included. I aim to put it together in the next few days.

Now, I did some basic soldering and desoldering in the past; I know how to keep my 25W Weller iron tips in good shape; but I don't know what are the "do"s and (more importantly) "don't"s of soldering an integrated circuit. I surely do not want to learn by trial and error!

Can someone experienced tell me if it's okay to apply 750°F to the pins of the ATmega's PDIP package when soldering through-hole, even if only for a second or two? If not, can I use something from the household as a heatsink? I only have lead-free solder, so I guess I can't solder at lower temperatures, but even so, the iron that I have isn't adjustible in that regard.

Thanks a bunch!

Soldering should not hurt the chip any but I really would suggest using a socket. The pins and pachages are designed to handle the rigors of assembly, not only bu hand, but mechanical assembly as well. The wave soldering systems put a lot of heat in one area even longer than soldering the pins one at a time.

The biggest problem with soldering is when you might have to remove the chip. It can be done but why make desoldering necessary?

Soldering is easy and pretty quick to do. Make sure the lands and pins are clean, or the solder may not bond. Make sure the iron is hot enough to do the job, (750 deg. is good) and routinely wipe off the tip to remove contaminant. A simple damp sponge does well, though I just use my jeans. A tiny amount of solder on the tip may be added to help transfer the heat to the work. Heat the work and add the solder to it.

Practice makes perfect.

I soldered my first board for my Beer ferment bot.

I also recommend a chip socket, It takes the worry out. Also I would recommend buying a cheap blank board from Radio Shack and practice on that first. It was a big help to me.

Don

mongo, Don, thank you very much for your tips! I already soldered the chip directly and it survived. I practiced on the jumpers and resistors first before tackling the pins. Actually, I realized that it takes just two or three seconds to make a clean joint: I would touch the pin and the board with the tip for one second to warm them up, then push the pin on one side with the iron while touching it with the solder on another, trying not to let it get whisked up by the hot tip. I soldered the pins in a "butterfly" fashion (starting from pins diagonally opposite, then moving up and down the chip, alternating sides) to keep any one side from overheating.

I'll get some sockets as well; it's good to know that I can simply extract one if I really really need it for something else.

Cheers!

I watched a bunch of videos on youtube before I tackled soldering. Go to http://www.youtube.com/results?search_query=how+to+solder for tons of clips and vids...

Here's a few quick tips for you...

A lot of times datasheets will specify the level of heat a particular package can take... In general you don't have to worry too much...

The amount of heat applied (assuming you have an adjustable iron) really depends on what you're soldering... Soldering to a big ground plane for example will sink more heat and require a higher setting... For most general work around 650 degrees will be more than adaquete...

One thing that might seem opposite to what you would think... Always make sure the iron is heated up to full temp before begining work... Also, don't try to back the heat down too much... When worrying about damaging an IC sometimes you might want to back the temp down considerably... That's sort of opposite of what you should do... With more heat you can "get in and out" much faster... If you have low heat, then you'll have to keep the iron on the connection much longer which allows more heat to conduct away into the chip... Hit it fast and the heat doesn't have much time to travel very far so it's a much lower temperature when it finally does...

Try to get the iron MOSTLY on the PCB pad... you want the bulk of your heat centered there... That doesn't mean you don't want to heat the pin as well, you absolutely do need to, but the pad will generally need a bit more heat to flow than the pin... Once it's heated just flow a bit of solder into the joint... It should flow nicely if it's heated... Then simply remove the iron and viola!

Last but not least... De-soldering is pretty easy... with the right tools... First off, take that silly "solder pump" you bought at radio shack and do something useful with it... Throw it in the garbage... or toss it to the dog to chew on or something... anything... just don't try to use it...

Okay, in all honesty a GOOD solder pump works fairly well, especially for larger node connections, but it's not really ideal... And most of them aren't "good"...

You can get a heated pump, those are really nice, but also very expensive...

The best option? In my opinion it's solder wick... It's a fine copper wire woven or braided into a mesh... It's infused with a lot of rosin... You just lay the wick over the joint to desolder, apply the iron (remember you'll need more heat now because of the additional load of the wick), and as soon as the joint heats up all the solder will be "sucked up" into the braid... It works great and is simple...

BUT... as mentioned, if you're going to be replacing a chip often, or whatever, sockets are the best option...

Rusirius - Thanks for the tips, everything makes sense. My soldering is less than sub-standard - that is, poor. I have quite a lot to solder at the minute, so with all the above advise in mind, I hope to improve in the coming weeks.

Thanks to all!

-Steve

No problem Steve... If I get a chance sometime here I'll try to post up a few pics to demonstrate a few things like a proper flow, cold solder joints, etc...

Greg

As for desoldering -- I don't have a pump nor the wick, so I came up with an alternate method. I heat the joint quickly until I see the solder liquefy, then I whack the board against a flat surface covered with a piece of paper. With a little luck and if I do it quickly, solder will leave the joint and drop on the paper, sticking there. It doesn't need to be a very strong whack either.

This works well for leaded solder and old PCBs that you do not particularly care about, for example when salvaging components from old ISA cards, TVs and such. I haven't tried with unleaded solder yet.

A trick I use is just simple canned air on the parts I want to remove. The only problem here is cleaning. It blows solder all over and you have to inspect everything for solder bridges but it doesn't stick and is easy to clean off.

I have done the board whack too. It works OK but you some times get splatter across in places you don't want. Be careful though with things like CMOS and older VLSI and similar chips. A sharp jolt can actually induce a static charge internally and destroy the chips.