Hi,
Do we need to apply heating after the solder paste is applied. I want to join back the line and contact on a flexi cable by applying solder paste. However, I am worried that heating is needed and might burn the cable. Or is there other alternative?
Paste needs to be reflowed.
jason_limkh:
Hi,Do we need to apply heating after the solder paste is applied. I want to join back the line and contact on a flexi cable by applying solder paste. However, I am worried that heating is needed and might burn the cable. Or is there other alternative?
You might be able to use a “circuit pen” or whatever it happens to be called; essentially it’s a paint pen filled with conductive ink. This only needs to dry, it doesn’t need to be heated. They are often sold as repair kits for rear window defrosters.
I had been waiting on my Lodestar paste to show up from Dealextreme.com so I could get in on this thread…
My paste showed up a few days ago in a flat pack. I am storing it in the fridge now and it seems to be just fine. I grabbed one of my old SMT boards, a bunch of spare parts and went to work. Since I did not have any kind of syringe to dispense the paste with, I went with my trusty X-acto handle and straight pin with the plastic head cut off (this makes a nice pick for general PCB work).
I dabbed small bits of paste on each pad and then placed a bunch of 0805 caps and resistors and also a few SOIC sized ICs for testing. I used a brand new $30 electric griddle from Target for reflow. At about 400 deg F, it flowed in minutes to a shiny silver. I let the board cool and then checked it out. I did get a little too much paste on the SOIC parts, so I had to go back a do a little wick clean-up. I’m sure with a syringe and small needle tip, I can avoid this next time.
All in all, I am very pleased with the results and I think I am going to give this a go on my next batch assembly (drop in external power adapter for one of my RC helicopter’s chargers).
The solder paste will deteriorate over time, the 'fridgerpcelectronics:
I am storing it in the fridge now and it seems to be just fine.
slows the process. In theory the paste will only last
six months from manufacture according to the vendor.
I’m currently using [Kester R276 solder paste.
When you get a syringe and needle you will find "dotting"rpcelectronics:
Since I did not have any kind of syringe to dispense the paste with, I went with my trusty X-acto handle and straight pin with the plastic head cut off (this makes a nice pick for general PCB work).
pads much easier. If in doubt put less solder paste
down, it saves a lot of time on rework.
Let the paste reach room temp each session.rpcelectronics:
All in all, I am very pleased with the results and I think I am going to give this a go on my next batch assembly.
Store unused paste back in the 'fridge.
Although the given shelf life is six months. I have
been using the same tube for two years (!)
No doubt it is less ‘fluid’ but solders up fine.
At first I used 26Ga needles and hand pressure,
now I have changed to 18GA needles, yet
it requires quite a bit of force to squeeze out
by hand. As a plunger I found a plastic highlighter
pen to be a good substitute. (I should have ordered
a plunger with the syringe…).
I was removing the needles each session
and poking out the needle with a wire. Now I just
leave the needle on and don’t bother to cap it.
It really helps to keep air out of the paste, the
manufacturers go to a lot of effort to have 'void-
free’ paste in the syringe.
An air driven dispenser with foot switch would be
a much better arrangement (as I don’t have
compressed air or nitrogen in my home lab, this
project is on my back burner, indefinitely).
Good luck! You’ll wonder how you got along without
paste solder for SMT assembly.](http://tinyurl.com/5ed964)
An air driven dispenser with foot switch would be
a much better arrangement
Or a stepper motor driver leadscrew to push against the syringe plunger. This allows the possibility of pulling back in the plunger right after a dispense in order to suck back any extra blob that may come out.
Combine this with an stepper motor XY stage for precise incremental pin-to-next-pin movements.
Good idea! Being careful not to suck air back into theUofMEShop:
Or a stepper motor driver leadscrew to push against the syringe plunger. This allows the possibility of pulling back in the plunger right after a dispense in order to suck back any extra blob that may come out.
needle…
I have used the [pneumatic dispensers. Its a
[commercial product, plug and play (as long as
you have air or nitrogen gas lines to your bench).
If I do more than five or six PCBs or the same design I'dUofMEShop:
Combine this with an stepper motor XY stage for precise incremental pin-to-next-pin movements.
farm the work out. When you do a lot of onesey-twosey
prototype PCBs the best method is to have and use
manual tools. Your idea is solid but once its up and
running the overhead to either program it or generate
XY data tables from the PCB artwork would be a time
killer.](Digital Syringe Dispenser | Timed Fluid Dispenser - Dispensing Equipment For Any Fluid)](Syringe Dispensing Systems | Industrial and Laboratory, Air Powered or Manual Syringe Dispensing - Dispensing Equipment For Any Fluid)
the overhead to either program it or generate XY data tables from the >PCB artwork would be a time killer
The XY stepper motor stage would not be programmed from the PCB artwork to move over the entire board layout. Instead, its initial position would manually be set to one pin’s location. Then the stage is just told to increment the known distance to the next pin, the solder is dispensed, and the stage is incremented again. So the initial positioning is still done manually but after that the fixed distance between pins is taken advantage of. Steppers are not even really needed - some sort of micrometer positioner with ability to move with sufficient resolution would be ok.
How does the auto increment know how many pads onUofMEShop:
Instead, its initial position would manually be set to one pin's location. Then the stage is just told to increment the known distance to the next pin, the solder is dispensed, and the stage is incremented again.Bigglez:
the overhead to either program it or generate XY data tables from the PCB artwork would be a time killer
the device (and the row spacing, or number
of rows)?
Sounds a bit [Heath Robinson to me…](W. Heath Robinson - Wikipedia)
The Pulsonix software I use can be set up to generate a file for controlling solder paste deposition. Most other packages can probably do the same.
Leon
For those pick and place machine, is there a standard control protocol for these Industry machines?