Heya folks, Crow here. Today I present the first half of another story from my engineer friend Paul Schreiber, this time from his stint at Research in Motion.
Date: Around Sept. 2010
Location: Irving, TX
Company: RIM (aka “BlackBerry”)
I was ready for my first design, after “learning the ropes” for a few months. Another engineer had switched divisions, and I was to get this phone into final production. There were prototypes, but the design needed ‘cleaning up’. We had 4 months to get working protos to the carriers for their internal testing. I was in the analog audio group, we also did some power supply work, speakerphones, mics, the vibrator motor, odds and ends. The schematic was huge, over 45 B sized pages. The part I was interested in was only 3 pages, but of course I looked at *every* page intently.
This was a “mid-volume” phone, 2 variants (GSM and CDMA, the types of radios for the carriers) and so we were ‘only’ looking at building around 3.5million/yr. But this means your BOM (Bill Of Materials) in the Excel spreadsheet goes out to 6 decimal places. Like a 22pf 0402 10V cap was $.000674ea. Did you realize the average cell phone has over 600 capacitors?
Like every consumer product ever designed, we were over budget. My goal was try to get $0.035 out of the design (times 3,500,000 = $122K or my salary). MORE would be better, of course.
So, I got the BOM with the pricing and a SAP account. Now, if anyone out there reads ‘SAP’ and hears the “Jaws” theme, you have dealt with SAP. SAP is a German company that sell the ‘back end’ of MRP (Material Resource Planning) software and the “front end” (the user GUI) is custom-made for every company. SAP horror stories abound, and it does play a part (cough) in this MTT.
OK, so I get the schematic and sort the BOM by price. Then, I apply the filter to only show parts on my 3 schematic pages. So far, so good. I start going down the list, most expensive to least. I stop dead in my tracks when I spot this:
1ea Capacitor, dual, matched 4N7 16V 0603 $0.1134
Wait, what? There is an 11 cent capacitor, that is a dual matched thing? Why? Except for some giant 100uf 6.3V tantalum caps (that’s another MTT) the other caps are ALL < $0.0045ea. Let’s see where this bugger is used! (Can anyone guess where, in a typical cellphone’s audio path, where this was used? Answer in pt.2)
I went to SAP to be sure the price was correct. The Excel was generated by SAP, there could be a data entry error or something (maybe it really was $0.01134, that sounded right). Log into SAP, type in the part number, ah… nope. Shows up as $0.1134. Then I see something else, the “Where Used” field. This lists the top-level BOM for every RIM pcb that has this part on it. And it was…blank?
So, I call the capacitor buyer in Canada, she was very nice and I gave her the standard “I am new and I hate SAP and I need you to check this part’s price for me” speech. She verified the price WAS correct and the Where Used was blank, because no released pcb used it. It was in the system because the prior EE had needed a custom pcb footprint made. I said OK and hung up the phone.
Well, screw that 11 cent matched-my-ass cap (I pulled the specs, it was a 5% *value* tolerance but the 2 caps were *matched to 0.5%*. YIKES! Well I saw where that cap was used, yes, 5% was correct and in *theory* matching these caps would be *ideal* but not in THIS use case. So, I took it out and put in 2ea 4N7 0402 caps at like $0.00011ea.
Folks, I just saved RIM over $340,000 for 1 hour’s work. I FREAKING ROCK!!!
I spent the next 2 weeks revising stuff, getting second sources, etc. and at the end of the exercise had saved the design $0.16442 or a total of $575,470. DAMN I’M GOOD. So, I write up the ECO, order new PC boards for testing, and wait for the promotion.
Except that’s not what happened…
(to be continued)