EEVblog #181 - Dead Bug Prototype Soldering

[justinc]

That was an interesting blog Dave, I can see I'll need glasses or a decent magnifying system to be able to do work like that.

I did wonder though if there was a socket you could have used, at least in the development phase.

The Scrooge in me likes to be able to reuse as much as possible and dead bug style for development, for me anyway, will probably result in literally a dead bug.

[justinc]

Hmmm an Uh Duh moment! Just read the comment on YouTube and I am just repeating what others are saying.

You answered my question there too, in that you were busting to try the chip out. I hear you mate. Been there myself.

[Ed.Kloonk]

Dave, you left out a very important aspect in this video..

How can you do this type of soldering when you have the DT's?

 

[Rufus]

I have dead bugged an analog version of the same part. The package is actually a tiny PCB encapsulated on the top with pads on the bottom.

A good tip would have been not to bother wiring up the 3 no-connect pads on the part 

[pmrlondon]

This technique would probably take me a very long time - fiddly work is very difficult for me and just gets more difficult the more often I have to attempt the same bit - I have CMT which doesn't help. However, it's a good technique - have seen similar things done on other types of package, and added a few components occasionally in similar style.

Anything involving soldering little bits of wire on is fun - preparing a 4164 to replace a 4116 being a good example.

[Mechatrommer]

just watched it. i think you should realized how bad it is doing the job under one magnification device (with hand). almost laugh remembering my experience of almost soldering my another hand during one job, not to mentioned the jittery iron that almost crash my control feedback loop in my brain. i never solder under a glass anymore, i just use it for checking after that for short and disconnect joints. but thumbs up to the video, thats what a hobbiest need. but dont forget the joke, it will keep my brain fresh free out of trouble. dave, where's your jokes going lately?

[mcu]

Thanks for this blog post. I have been wanting to play with accelerometers for some time, so I gave the soldering a go.

On my first attempt at soldering I was using solid core wire. This put too much strain on the LGA pads, and some pads ended up coming off the the IC (especially when the IC was warm). I used the remaining pads as a testing ground to see how I could improve my technique.

Second time round I used multicore wire. It was a fiddly job, but gladly no pads became detached from the IC.


I was using a chisel-ish tip.


The pads can become detached from the IC very easily, so strain relief is a must. I filled the entire board with hot-melt glue.


It looks quite cool...but does it actually work? Off to test it, wish me luck!

[IanB]

Thanks for this blog post. I have been wanting to play with accelerometers for some time, so I gave the soldering a go.

On my first attempt at soldering I was using solid core wire. This put too much strain on the LGA pads, and some pads ended up coming off the the IC (especially when the IC was warm). I used the remaining pads as a testing ground to see how I could improve my technique.

Second time round I used multicore wire. It was a fiddly job, but gladly no pads became detached from the IC.

Holy smoke! That looks like trying to thread a needle with a rope!

Next time what you should do is separate individual strands from the multicore wire and use one single strand to connect to each IC pad. You can use a conical tip on the iron to help touch the wire down on each IC pad.

It's possible the pads came detached using excess heat rather than mechanical stress. What you need to do is tin the pad, tin the wire strand, add flux, and just touch the wire down on the pad with the iron.

[mcu]

Holy smoke! That looks like trying to thread a needle with a rope!

Next time what you should do is separate individual strands from the multicore wire and use one single strand to connect to each IC pad. You can use a conical tip on the iron to help touch the wire down on each IC pad.

I was able to use this wire without too much trouble. Any thicker would have really been a challenge. Your suggestion on only using some of the strands is good.

It's possible the pads came detached using excess heat rather than mechanical stress. What you need to do is tin the pad, tin the wire strand, add flux, and just touch the wire down on the pad with the iron.

Yeh I just tinned the connections and tacked them down. I tinned the IC in one go by using drag soldering. This method works a treat. The tip I used is very slightly concave, which helped.

The pads come off very easily when the IC is warm (i.e. during soldering). Even after the IC cools down, it doesn't take much effort to pull a pad off. I had to be very weary of both mechanical and thermal stress when soldering this package. That's what made the soldering difficult...one wrong move and off comes a pad.

I avoided the problem by minimising stress on the joints wherever I could. I used multicore wire for flexibility. The wires were cut to the right length so they don't bend and put pressure on the pad. I also left the soldering of this LGA package until last, so that I don't have to move the wires any more after they are soldered down. Then I filled the board with hot glue for strain relief.

[Mechatrommer]

It looks quite cool...but does it actually work? Off to test it, wish me luck!

dude! i thought i'm the worst here.

[mcu]

A video of testing: