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Soldering an ecu

April 10th, 2008 · No Comments

Soldering

This “black art” of the electronics industry is shunned and feared by many.

There is no real reason for it though, because with the right tools and some practice anyone with a steady hand can solder basic electronics. Okay, I must admit that like with all arts, there are some geniuses running around that can make the tiniest pitch of smd look like it was done with an smd placement machine. This article is to make things clearer for the beginner that wants to start soldering his own electronics projects.

I will use the example of an MSA15 ECU with two plcc32 smd eproms and step by step I will discuss the equipment needed.

  1. Like with all projects you are going to need a clean workplace and the objects you work with should be clean of grease and grime. Because it’s hard to reach some parts with a rag or cottontip there is a thing called a fibreglass brush. This brush allows you to remove things like a protective laquer, dirt and oxides from the pcb.

This is also very handy to clean small rustspots on your car btw.

  1. You need good lighting and a magnifying glass to visually inspect your work.

You can buy special lenslights for this, but I often use the halogen headlight and a Sherlock Holmes device. The added benefit is they make you look very sexy when using them.

  1. Removing components can be done in many ways. I won’t discuss the lighter method or the paintstripper gun or baking the thing in the oven, as those methods are Mack Guyver methods. The old people among you will know who I am talking about.

 

Soldering wick acts like a sponge for soldering tin.

What you do is you place it between the iron and the solderjoint and as it melts the solder gets sucked into the wick. Ideal for cleaning the solder pads when the components is removed. Once a piece is filled with tin, cut it off as you don’t want to loose heat into that unused bit.

 

Suction pen. They come in heated versions too.
this cheap version requires you to add more molten tin onto the solderjoint and then you push the preloaded spring pump on the tin and press the button. The solder gets sucked into the pen and your joint is almost free of tin. This is only useful on the through hole components, not so much for smd.

Hot air station. This is something you should have if you ever want to solder smd. It preheats air to high temperatures and then blows it through the nozzle onto the joints. You can get special sized buckets and nozzles for all kinds of component packages.

For our ecu we just use the hot air station and keep moving around the chip in circles. Gently press and lift the edge of the chip so until you notice you can move it, this is where you flick it off the pcb. Be careful though do it too soon and you lift some solderingpads off the board and you’re in for some hours repairing the board.

 

  1. Once the old chips are removed we clean the soldering pads and the chips with the soldering wick.

  1. We are now ready to solder on the sockets using our soldering iron and the tin.

Soldering tin comes in many gauges and mixtures. Lately there is the whole ROSH electronics where tin is supposed to be lead-free. Don’t worry though our old ecus still have plenty of lead in them. So get the leaded tin, it’s far better than the unleaded.

A gauge of 0.6mm is what I prefer for this kind of soldering.

Flux is a chemical product that helps the solder flow onto the metal of the pads and pins. There is the brush on kind and the kind that comes in needles. Get the one in needles as it’s easier to apply in the small space we need.

Soldering stations come in many shapes and sizes, you should get one with a few tips, fine enough to work with the smd stuff. They often have a sponge included. A wet sponge and a hot soldering iron are great for removing excess tin from the tips, you just smear it over the sponge and you’ll see it turns nice and shiny again.

As for temperatures I go for around 350 degrees celcius for this stuff.

  1. We apply some flux over the pads and we put a dab of solder on two opposing corners of the padgroup of each eprom.

  1. Take your socket, press out the plastic bottom end and line it up to the pads of the pcb. Now press it down as you heat the pins that lie over the dab of solder in the corners. This way we anchor the socket and we are now free to use both hands to guide the tinwire and the iron onto each pad and flow some solder on it. You will notice that the flux melts and draws the solder onto the pads with a nice shiny surface.

 

    1. Use a cotton tip and some alcohol to clean the flux off  the pcb.
    2.  Once we have both pads done, we can then visually inspect the job with the Sherlock Holmes device and insert the new chips.

    Tags: Chiptuning · Technical