Procuring the Parts

April 27 2016

The schematic is done, the layout is done, the BOM is done. Today's task is to order the parts.

I need to have the parts in hand to build the paper board, which I use as the final verification of the fit and size of the components before placing the PCB order.

I am ordering an initial build kit for 10 boards, which should be enough to see me through the paper boards and first set of real boards.

I created a new Excel sheet for the order, copied the PartID, VendorID, Qty, and Description columns. I weeded out the non-Digikey parts and uploaded the CSV text file using My Digikey > Parts List Manager. Digikey then built the order and presented it for review.

There were a couple glitches:

• The Abracon 32KHz crystal (PartID 2) is out of stock with a 4 week lead time.
• The microUSB connector (PartID 4) is marked as in stock but obsolete.
• The 100uF radial cap (PartID 42) is out of stock with a 11 week lead time.
• The TC33X adjustable resistor had the wrong VendorID.
• C227 was wrong in the BOM (corrected from 470nF to 4.7uF)
• Remove the A3967's, I have enough.
• Remove the red led (Digikey 511-1653-6-ND), I have enough.
• Remove the orange led (Digikey 160-1180-6-ND), I have enough.
• I need to add prices for full reels and 1000-count Digi-Reels to my pricing spreadsheet. Some of the resistors are $13.20 for 10,000.

Reels are easier to manage than cut tape, but I need at least 100 units (preferrably 1000) to load the tape into an autofeeder. I will lose the first 250mm of components when loading cut tape into an autofeeder. 0402 parts have a pitch of 2mm, resulting in 125 lost components. 0603 parts have a pitch of 4mm, with 62 lost parts. 1206 parts have a pitch of 8mm, losing 32 parts. If I decide to purchase less than twice the wastage on cut tape, the component should be resized to 0603 or larger to reduce autofeeder waste or make them easier to manage on the tray.

I am replacing the out of stock 32KHz crystal (PartID 2) with the through-hole equivalent, which costs about 1/10th as much.

The new order (cart "CtrlMtr01") totals $691.34. I still need to compare the order to my inventory to make sure I am not ordering parts I already have. This does not include the $180 for the PCB's or the $35 for the stencil.

I forgot to replace the 100uF cap 493-11989-1-ND), which has a lead time of 10 weeks. The UKZ1E101MPM (Digikey 493-3190-ND) has the same footprint, lower rated lifetime, slightly cheaper.

The cart is now $688.23. The build(100) cost per board has now dropped to $29.99.

I reduced the quantity of the MSP430's and USB hubs to 5 and submitted the order on 4/28. The final total was $650. Everything was in stock for immediate delivery so the kit should arrive on Tuesday afternoon.

I spent two days building the order, including the time spent to replace the out of stock parts. The next step will be loading the parts into the machine.

May 3 2016

The parts arrived today. I spent an hour or so entering them into Inventory.