PCB Assembly Services - Screaming Circuits: PCB Assembly vs. Mondayitis


PCB Assembly vs. Mondayitis

I pulled up an older MCU and motor driver board of mine this morning. It's a project from about ten years ago that I haven't had built since 2016. It's still a nice design. In 1.3" x 2", I have a PIC MCU, and LiPoly battery management chip and a 2 by 1 Amp Toshiba motor driver chip. It also has seven I/O on 0.1" headers, each with power and ground pins, ICSP, I2C USB and RS232. It's a great hobby robot board that I've had a lot of fun with since designing it.

The problem is that, while none of the components are obsolete, several are pretty hard to come by these days. In fact, none of the four integrated circuits I originally put on the board are PIC18LF4 low stock currently available. Anyone who is designing today knows that this is not a symptom of this board being a ten year old design, so much as this is just the way things are these days. I have to go through and find subs for each of these, and lament that a few won't have drop-in subs at all.

The PIC micro should be the easiest as they have a wide selection and as long as the replacement has the peripherals that I am using, I can sub it with minor code changes. I just need the keep the same footprint: an 8x8 mm, 44 pin VQFN.

Out of 25 listings for any PIC18LF44, in the 8x8x44 package, one part has 4 in stock, one and 5 and one has 238 in stock. None of that gives me enough security to use as a sub. Next I tried searching DigiKey for PIC18F44, PIC18F4, PIC18F, PIC18. None of these broader searches showed enough stock such that I would be comfortable using as a sub unless I were to order the parts today, which I'm not.

The PIC micro should be the easiest to sub of my four ICs.

At this point, I decided to quit for lunch.

Maybe forever.

Duane Benson
1 Mondayitis / mun·day·itis/ verb 1. The near-instant decrease in ability to focus on the task at hand on the realization that you have nearly a whole week ahead of you before the next weekend. 2. An increase in tension as the influence of the prior weekend fades out. 3. / noun / A not yet unidentified small crawling insect found by turning over a rock in your driveway. See also Getoutitis

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I've been down this same path for so many parts. We're designing boards based on the one part of a given type we can get. In one case, we're replacing a BGA on a dev board and testing it to verify the parts we bought from a broker are authentic.

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