I'm trying to solder these onto a homemade pcb....
There have 60 pins, each pin is tiny and has a 0.5 mm pitch.
I'm having the greatest difficulty in soldering these, so far I've made 5 boards, and got one to work.
So far I've had two techniques recommended to me, neither of which was very successful.
Firstly, I tried using a very fine tipped soldering iron under a 20 times magnification binocular microscope - I just haven't been able to hold the soldering iron steady enough to get this to work, and even the finest tipped soldering iron is so broad it tends to overlap and fuse two pins together.
Secondly, I tried using de-soldering wick to solder several pins at the same time (i think I saw this in a sparkfun video). this works slightly better, but I still find that some pins get no solder, and others get fused together with their neighbors.
The final technique I've seen (on a video I can no longer find) involved using a broad-tipped soldering iron, and magically wiping the iron over the pins to solder 30 pins with a single swipe - I've no idea how this actually worked, I think the guy cheated and just used magic instead of any conventional techniques!
Anyway, can anyone give me any better tips? any advice gratefully received.
Some background - the boards are made using the UV / photomask / etchant technique, and are chemically silvered before I start soldering. I've done a fair bit of soldering (through hole components only) in the past and consider myself reasonably proficient at this, I've only recent started working with SMC components but have managed this without too much difficulty when the pitch spacing is large enough.
The boards I use are HASL, so tin your pads thinly with solder first.
Plenty of flux on the whole pad area - use a flux pen.
Line up the chip / connector - and add more flux. Flux is your friend.
Using a pointed iron melt the solder on each of the pads in turn to make it flow onto the pin. Pushing the molten solder up to the pin can help.
I never need to add any solder or tin the pads - the solder in the HASL is more than enough - you only need a tiny tiny amount. So when you tin with solder it might be worth removing as much as you can with some solder braid to keep the quantity down - you don't want the solder really to be raised up from the surface of the pad much at all.
I regularly hand solder 0.4mm TQFP chips with this method and it works perfect every time.
Thanks guys - i haven't been adding any extra flux, I've been relying on whats in the solder. - looks like this is where I'm going wrong.
The boards I use are HASL
Sorry, but what is this?
I've just seen a youtube video that suggested that SMD soldering can only be done on boards with solder resist laquer (the green or red varnish that professional boards come covered with) is this true, does this mean I'm not going to manage this with home made boards?
I've just seen a youtube video that suggested that SMD soldering can only be done on boards with solder resist laquer
That's either bad advice or I have been very lucky. I make my own SMD TSSOP-28 boards with just toner transfer, lots of flux and my standard Hakko FX-888 soldering iron.
Yes all of the above especially the flux and the Hakko and tin the pads first... Hakko sells a knife edged 45 deg tip that I've found perfect for soldering a SO-16 IC in place with two applications of the iron, one on either side. It's also unbelievable for 'flipping' resistors and capacitors off a PCB when things need 'modification'.
