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Messages - Tim

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1
Support / Simblee MSL
« on: May 26, 2017, 06:50:09 PM »
Hi all,

Have been learning all about MSL (Moisture Sensitivity Level). Recently, distributors have been affixing MSL caution labels to the ESD bags Simblees are shipped in, stating level 3. I wrote support@rfdigital.com and received word that Simblee is actually rated MSL 6. This means chips need to be baked (8-12 hours at 125°C) before mounting/reflowing, and following baking, the chips need to be mounted/reflowed within 6 hours.

We've never baked before mounting/reflowing. We've been hand assembling (using stencil to apply solder paste, hand placing components, including Simblee, then reflowing in reflow oven) and have been getting a failure rate of around 1 in 10. I'm waiting for reply from RF Digital with their opinion about the possibility that not baking Simblee before mounting/reflowing is contributing to the failure rate. Although we are not happy to learn about the baking requirement (which increases assembly time and cost), we'll be happy if baking prior to mounting/reflowing reduces our failure rate.

Any experience out there?

Many thanks,

Tim

2
Support / Re: hand soldering Simblee module?
« on: May 25, 2017, 08:16:00 AM »
Hi Anthony,

You might find this thread helpful:

http://forum.rfduino.com/index.php?topic=1735.0

Cheers,

Tim

3
Support / Re: Simblee assembly and pick'n place machines
« on: May 25, 2017, 08:08:03 AM »
Some new information to share ...

Have been learning all about MSL (Moisture Sensitivity Level). Recently, distributors have been affixing MSL caution labels to the ESD bags Simblees are shipped in, stating level 3. I wrote support@rfdigital.com and received word that Simblee is actually rated MSL 6. This means chips need to be baked (8-12 hours at 125°C) before mounting/reflowing, and following baking, the chips need to be mounted/reflowed within 6 hours.

We've never baked before mounting/reflowing. I'm waiting for reply from RF Digital with their opinion about this possibly contributing to the failure rate we are experiencing. Although we are not happy to learn about the baking requirement (which increases assembly time and cost), we'll be happy if baking prior to mounting/reflowing reduces our failure rate.

Any experience out there?

Many thanks,

Tim

4
Support / Re: Simblee assembly and pick'n place machines
« 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

5
Support / Re: Simblee assembly and pick'n place machines
« 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

6
Support / Re: bad Simblee batch?
« on: April 24, 2017, 02:21:25 PM »
We'll be receiving more Simblees from DigiKey tomorrow and will be assembling. Results will be revealing. I also noticed different colour, but that could be because of rework. These are chips that were removed from boards after failure.

We recently ordered from Mouser because they were $3 cheaper. It could be coincidental that we started having assembly issues with this batch. Will post more here as we learn.

Thanks!

7
Support / bad Simblee batch?
« on: April 23, 2017, 01:14:33 PM »
Hi ..

Trying to explain why we're getting a high failure rate on assembling our boards. We recently ordered from Mouser and received 30 Simblees packaged as in photo, which means someone handled them to take from factory packaging and place on foam. Also found a label on the anti-static bag containing the Mouser order that have never seen before (see attached photo). Wondering about possible ESD events during handling and shipping that damaged chips. Previously all Simblees came from DigiKey and in original factory packaging and we had a much higher success rate. Wondering if anyone has had issues with Simblees arriving defected from different suppliers.

Appreciate any thoughts, experience.

Tim

8
Support / Re: Simblee assembly and pick'n place machines
« 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.

9
Simblee Libraries / Re: Simblee library 1.1.1
« on: April 02, 2017, 04:24:33 PM »
Thanks Tolson. Has 1.1.1 proven to be a stable release for iOS platform?

10
Simblee Libraries / Simblee library 1.1.1
« on: April 02, 2017, 08:28:19 AM »
Hi ...

I see that Simblee library 1.1.1 is available, but don't see any announcements about it. Anyone aware of details of the update? Release notes?

Thx,

Tim

11
Support / Re: Simblee assembly and pick'n place machines
« 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

12
Simblee Libraries / Re: SimbleeBLE affects TIMER1/2 accuracy
« on: March 30, 2017, 08:08:12 PM »
Thanks for posting RF Digital response. Good news indeed. Glad the post has been helpful. It's been fun learning.

Cheers,

Tim

13
Support / Re: Simblee assembly and pick'n place machines
« 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

14
Support / 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

15
Simblee Libraries / Re: SimbleeBLE affects TIMER1/2 accuracy
« on: March 19, 2017, 08:38:05 PM »
Hi Jeff,

Yes, micros() is inaccurate when BLE is on due to priority of the BLE stack. That's what led me to use PPI, GPIOTE and TIMERs because they are not subject to CPU or BLE. Not sure about delayMicroseconds(), but I presume same issue. micros() is just reading the value of RTC1, so if you could use PPI and GPIOTE to start and stop RTC1 and read it's value in an interrupt routine, that might do the trick. I don't have much experience with encoders, so I might be way off here.

I'm very interested to hear RFDigital's response. If you're using PPI, GPIOTE and TIMERs to "handle encoder interrupts," my understanding is it should work.

Thanks for adding to the conversation.

Tim

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