Hello Element14 community.
Last week I received reward for asking best question on webinar organized by Element14 and KEMET. The reward is capacitor engineering kit containing 42 values ranging from 0.2 pF to 100 pF. All in 0805 package. Kit contains 50 pieces of each value, 2100 capacitors in total. The capacitors are not the general purpose one, but instead all of them are from KEMET CBR serie which targets RF application and capacitors are optimized for this purpose. It is the serie which was presented the on webinar. On the Internet you can find this kit under name CER ENG KIT 45.
CER ENG KIT 45
The kit is in the plastic box which at the first look like box for a CD. But this plastic box is much larger. In fact I expected it smaller but I am not good in estimating sizes before I see the thing. Dimensions of the box are approx. 30 × 27 × 3cm.
The capacitors are stored on three pages in rows. They are under plastic transparent cover and you can pull the tape and push it back from side.
Capacitors are in standard tape which you may know if you ever bought capacitors in 0805 form factor. At sides there are labels. At left side is human readable description of package size (all are 0805 in this kit), capacitance (differs per capacitor) and voltage rating (all are rated 500V). On right side there is exact part number for the capacitor stored in that row.
Kit contains full EIA E6 and E12 series in range 1 – 100 pF. Except E6 and E12 it contains few capacitors from E24 serie and also contains values between 0.2 and 1 pF in 0.1 pF step.
E6: 1pF, 1.5pF, 2.2pF, 3.3pF, 4.7pF, 6.8pF, 10pF, 15pF, 22pF, 33pF, 47pF, 68pF, 100pF
E12: 1.2pF, 1.8pF, 2.7pF, 3.9pF, 5.6pF, 8.2pF, 12pF, 18pF, 27pF, 39pF, 56pF, 82pF
E24: 0.2pF, 0.3pF, 2pF, 3pF
Other: 0.4pF, 0.5pF, 0.6pF, 0.7pF, 0.8pF, 0.9pF, 4pF, 5pF, 6pF, 7pF, 7pF, 8pF, 9pF
KEMET CBR
KEMET CBR is serie of capacitor which is optimized for RF applications. In comparison with general purpose capacitors, it differs in materials used. From practical point view capacitors in this family have very low ESR and high Q factor. I am not very experienced in this area yet, so for better explanation I recommend watching KEMET webinar on-demand here.
The first capacitor which I pulled from the kit is 22 pF one:
My first test of this capacitor was for tuning NFC antenna on my own NFC tags which I did at the end of the last year as part of Project14 RFID and NFC competition. At that time, I had no RF specialized capacitors and my collection of capacitors in sub 100 pF range was very small. I originally did tuning by stacking several capacitors for making the right value. I was soldering and desoldering them until I find the best option. It of course is not the most professional way to do this, but it worked. Today I took my NFC tag with double sided antenna and replaced stack of two general-purpose 10 pF capacitors by single 22 pF capacitor form the kit (CBR08C220JCGAC). Here it is soldered near NFC tag chip:
Previous solution with general-purpose capacitor was detected by iPhone in range of 3-4 cm. The new solution with RF optimized capacitor has slightly better range. In 10 attempts tag communication happened when tag was between 4 to 5 cm from phone. I did not expect visible improvement and it surprised me a little. I personally think that it is not caused by better structure of capacitor but rather by better overall accuracy because now I use single capacitor instead of two stacked.
Because now I have more precise capacitor, I can experiment with capacitance anymore. When I was making tags last year the 10 pF was the smallest steps which I was able to do, now I have much more options. I tried replacing 22 pF cap by few other capacitances around 20pF and find the best option 15 pF cap in which I was able to communicate with tag in range between 4 to 6 cm which is the best range I achieved with my custom NFC tags.
The last good property of KEMET CBR caps which I want to mention is solderability. Hand soldering caps with tinned terminal is much easier than nickel-plated general-purpose one.
Conclusion
After first few hours spend with the KEMET capacitor kit I am satisfied. I do not do RF circuits regularly, but I want to learn some stuff in this area and in few years this kit will be helpful to me, I think. My first impression is positive. At the end I would like to thank Element14 for shipping me the reward and organizing the webinar and also, I would like to thank KEMET for sponsoring it. Thank you very much.