Speed of placement

[markoseverin]

Hi Guys,
I have a question about the speed of component placement. I have an LED strip made of a rigid PCB (standard 1.6mm, dual sided) which is 40cm long and 3cm wide. On the strip there are 300 components; not many different ones but lots of repeats (LEDs and resistors). I'm considering two options:

- 2 PCBs per panel (600 components)
- 3 PCBs per panel (900 components)

I've read somewhere that the LitePlacer can do 500-800 components per hour, but I haven't managed to find out, if this is the time with or without the bottom vision. I'm planning a mass production of anykind, certainly not, but my concern is, that if I go with the 3 PCBs/panel, the time to place the components would be too long for the solder paste. I've read through various forums that for solder paste the maximum time it can be in free air is 2h, but by my experiences in 2h the flux is already evaporated.

What are your suggestions? I need to make about 50 of these PCBs. I'm leaning more towards the 3 PCBs per pannel to minimize the manipulation time (solder paste printing takes just as long if there are 2 or 3 PCBs), but I am worried that the solder paste would get dry during the pick&place time.

Thanks for any advice,
Marko

[AnalysIR]

I suspect the 500-800CPH is the theoretical max with everything optimised.

From memory I managed to get <250CPH at best. It really depends on your individual config. If you are checking the tape-hole with vision for every pickup it would be slower. If you have an accurate jig or feeders it could be much faster)

If you are using an automatic feeder close to the PCB for 1 single component, I expect you might get to the higher end of CPH.

The other bottleneck I found was running out of components on a tape for high component count parts on a panel. This means you have to redo the exhausted tape during the job which kills the average CPH number. Of course designing the job with multiple tapes for the same component can overcome this (C1_TapeA, C1TapeB etc etc)

Re Panel size....you can always break the larger panel apart as needed as the fiducial calibration should eliminate any offset issues.

Bottom vision only works with OpenPNPAFAIK (comments above are based on LP software)

As you know, LP is intended for prototying / low volume runs, but with a 'tuned' setup this can be exceeded.

[KeithM]

Marko, consider using Loctite GC10 paste, it will take much more than a couple hours to dry out to the point that it will not provide good reflow results. I have been using this paste for over a year and am very happy with it.
Keith
(edited to fix typo)

[JuKu]

If GC10 would have been available a few years ago, very likely LitePlacer would not exist. I would use a whole day, maybe a day and half to place the parts on more complex prototypes and still do audio product development projects. (I haven’t had a full product development project for a few years).
https://liteplacer.com/about/the-story/

[markoseverin]

Hi,
Thanks for the input. I've done quite a bit of research on the amount of time the paste can be printed before reflow. It turns out that the 2h figure I had in my head was just for one paste (cannot remember anymore which one). It seems most can do 4-8h, which is surely enough for the 900 components I plan to place.

Anyways, the GC10 is a RoHS paste and ad such is a pain to use because it requires high temperatures. Sure, you can reflow the LEDs, but then if you have any rework, you'll probably melt the LEDs white plastic, before you manage to desolder them. I've done a few manually placed boards with this stuff:

https://uk.rs-online.com/web/p/solder-pastes/1462877/

It's a low temperature paste, uses Berillium, and it melts at 137°C. Apparently this stuff was used by IBM in the 80s for some temperature sensitive components. With this paste, I set the reflow oven to peak at 180°C and it works beautifully. It does not stress the LEDs as much as the standard RoHS pastes and is easy to reflow.

Thanks again for the help,
Marko

[wormball]

> It's a low temperature paste, uses Berillium, and it melts at 137°C.
> Sn42Bi57Ag1

It is not beryllium, it is bismuth.