Author Topic: Simblee Heat Damage  (Read 1161 times)

lellasone

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Simblee Heat Damage
« on: February 21, 2016, 03:14:38 PM »
Hi All,

I am working on creating a garage door opener remote using Simblee. I have successfully soldered my Simblee chip to my PCB, and have verified that it is working well (to the extent of serial reads and turning on an led). However, when I upload a Simblee mobile sketch (currently using thermometer) the app won't open, and I get very poor signal even a few feet away.

It took me a while to solder the Simblee (during which time the board and Simblee were both in a pan on the stove) so my current assumption is that I damaged the radio during that process, but I thought I would check and see if anyone has run into similar symptoms.


bsiever

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Re: Simblee Heat Damage
« Reply #1 on: February 22, 2016, 05:12:09 AM »

Did you leave the area by the antenna free of copper?   It doesn't look like the data sheet specifies a copper-free area like the RFduino's sheet does.  Perhaps others on the forum with RF experience can suggest best practices for a layout and you can see if your board meets them.

tolson

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Re: Simblee Heat Damage
« Reply #2 on: February 24, 2016, 03:00:21 PM »
bsiever is correct. You can not have any copper pours, traces, or metal parts on the antenna end of the Simblee. You can use the RFduino datasheet examples for trace, groundplanes, and component placement the same as for the Simblee. BooCoo examples are given from page 22 through 36.

http://www.rfdigital.com/wp-content/uploads/2014/03/RFD22301.Data_.Sheet_.11.24.13_11.38PM.pdf

 You can see from the examples if you place your RFduino/Simblee in the middle of your board you have to waste half your board space to no parts.



 So always put it as close to the edge/corner as feasible.



The other consideration is the pads are so small and close together and are easily shorted with solder. Did you use a stencil to lay down your solder paste?
Using the frying pan method has its own issues. How flat is the pan to board interface which can cause uneven heating hotspots.
I don't know how the Simblee QFN style chip is actually built, but I presume/hope the package is molded/potted around the internal parts consisting of two crystals, the bare silicon version of the nRF51822, chip antenna, and supporting passives. That a lot of stuff to cram into such a small space. If so, I doubt you caused any internal parts to become unsoldered/delaminated.

If you can program it with a test program and receive back serial monitor data, one would assume the chip is OK. Normally, getting a fair radio signal even without an antenna is do-able. So my bet without seeing your board/project layout is that you have metal component/traces interfering with the near field RF.

Can you show us the community your board layout?

Here is an example of my layout. I put the chip in the corner of the board and keep layer planes and traces away from the upper part of the Simblee QFN.