Author Topic: Simblee assembly and pick'n place machines  (Read 234 times)

Tim

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Simblee assembly and pick'n place machines
« on: March 28, 2017, 11:59:21 AM »
Hi all ..

Currently we're hand assembling our boards. Our PCBs are manufactured by OSH Park. We use stainless steel stencils by OSH Stencil. We use lead-free solder paste by MG Chemicals. We use the Whizoo reflow oven. We're not yet at a quantity that makes automated assembly practical.

The problem is that for about one in 15 boards we hand assemble, the Simblee has an alignment issue or an invisible solder bridge and does not work. It's time consuming to fix.

We are considering desktop pick and place machines both to eliminate this issue and speed up assembly. Does anyone have experience with any of these:

https://www.botfactory.co
http://www.liteplacer.com
http://visionbot.net
https://www.manncorp.com/component-placement-and-handling/manual-pick-and-place

Any others? Thanks for any thoughts, advice.

Tim

mjkuwp94

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Re: Simblee assembly and pick'n place machines
« Reply #1 on: March 28, 2017, 05:55:39 PM »
I don't have experience with any of those machines. 

How many are you making - can you justify the expense in $$ and time setting up the machine?

how about using the Z axis of a 3D printer to place just that one part with a vacuum cup?  You can make a fixture with the 3D printer and then orient the part on a bare board and place on a board after paste is applied.

Perhaps use leaded solder. I  am not an expert but just guessing it may perform better.

I've placed a few by hand same as you are doing and not had trouble.  However, i've only done a few.

Tim

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Re: Simblee assembly and pick'n place machines
« Reply #2 on: March 30, 2017, 08:05:35 PM »
Thanks for your thoughts. We might sell 500 in a year and hand assembly is fine given that quantity. Would like to discover a method that yields zero defects. For environmental reasons, would rather not use lead solder. Using a 3D printer sounds interesting. Would have to invest in one and then do a lot of learning, experimenting, but might be worth considering, so thanks for the idea.

Are you using lead solder? Any particular reflow oven?

Many thanks.

Tim

Tim

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Re: Simblee assembly and pick'n place machines
« Reply #3 on: April 01, 2017, 08:51:09 AM »
A couple new ideas that might be helpful?

First, would applying extra flux to the Simblee pads on the PCB before applying solder paste with stencil be helpful?

Second, after applying solder paste to board (with stencil) and before placing Simblee, how about melting the solder paste over the Simblee pads with a soldering iron to get the solder attached to the tiny pads. At that point could make sure there are no solder bridges. Then position the Simblee over the pads and reflow.

Thoughts? Thanks,

Tim

tolson

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Re: Simblee assembly and pick'n place machines
« Reply #4 on: April 01, 2017, 01:33:13 PM »
A couple new ideas that might be helpful?

First, would applying extra flux to the Simblee pads on the PCB before applying solder paste with stencil be helpful?

Tim
Hi Tim,

Pre-applying a smear of no-clean flux across the pads works good for me. I use SMD291. Also, I tend to mix a little ot the SMD291 into the solder paste making it thinner and more diluted.

Solder pastes come in different particle sizes. Perhaps a finer particle size is in order.

I do not use any solder on the four square ground pads in the middle of the Simblee.

Tim

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Re: Simblee assembly and pick'n place machines
« Reply #5 on: April 02, 2017, 04:26:57 PM »
Thanks Tolson. I'm hopeful that smearing flux on Simblee pads before overlaying stencil and applying solder paste will do the trick. Will post here again once we have a sense for helpfulness.

Thanks.

Tim

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Re: Simblee assembly and pick'n place machines
« Reply #6 on: May 14, 2017, 08:54:20 AM »
Some additional ideas in attempt to improve our hand assembly yield.

1) Change I/O pin assignment to reduce number of adjacent pins in use.

2) Remove from PCB any pads for Simblee pins not in use.

Reasonable?

Also, we've cleaned up our handling procedures to eliminate ESD events that could damage chips.

Thanks,

Tim

tolson

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Re: Simblee assembly and pick'n place machines
« Reply #7 on: May 14, 2017, 10:57:30 AM »
Hey Tim,

Sounds reasonable to me. I look forward to your further discoveries.

Although, ultimately, it would be nice to know what to do when a more I/O intensive project comes along.


Tim

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Re: Simblee assembly and pick'n place machines
« Reply #8 on: May 14, 2017, 01:49:45 PM »
Thanks Tom.

Another change in our process is to attach the programming header to the board before applying power to the USB shield. I understand damage can occur if I/O pins are connected before power is applied. The theory is beyond me, but I've learned this from a trusted source.

Tim

tolson

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Re: Simblee assembly and pick'n place machines
« Reply #9 on: May 14, 2017, 05:42:21 PM »
Thanks Tom.

Another change in our process is to attach the programming header to the board before applying power to the USB shield. I understand damage can occur if I/O pins are connected before power is applied. The theory is beyond me, but I've learned this from a trusted source.

Tim

Right.. Absolutely. I noticed some videos showing people that should know better inserting and/or pulling their shields apart while power is still applied. These devices are NOT hot swappable designs. For anybody that might read this... Always remove your powered USB and/or other power source before attaching and removing shields.