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2017 Manufacturing run

In preparation for [[Smallpeice 2017]] we manufactured 15 [[power boards|Power board]] and 15 [[motor boards|Motor board]].

Procedure

PCB manufacture

The PCBs were manufactured by Dirty PCBs. Two 10x10 protopacks of each board design were ordered, giving approximately 20 units of each board. One protopack of each type was ordered with a solder paste stencil.

The two protopacks with stencils cost $69.96 each, while the two without cost $44.95 each, totalling $229.82 of goods. Shipping (DHL Hong Kong) cost an additional $30, giving a grand total of $259.82, equivalent to £208.25 at the moment of purchase.

Useful links:

Component purchase

The canonical bill of materials is that provided by the designer of the boards. This is available as pbv4b_bom.xls in the power board hardware repository, and bom.xls in the motor board hardware repository.

The bills of materials for the two boards were combined into a single list, as this made purchasing and organising the components easier. Components which were unavailable, no longer manufactured or unnecessarily expensive were replaced with currently available or cheaper alternatives. Each type of component was given a reference number (often labelled as "SB BOM #") for easy identification.

Components were to be purchased from four UK suppliers: Farnell, Mouser, Digikey and Radio Spares. As the vast majority of the components were to be bought from Farnell, we successfully applied to their sponsorship programme, receiving all required parts from this supplier at no cost. The remaining few components were bought from the other suppliers through the university.

Each bag of components is labelled with its SB BOM #. As of December 2017, spare components are stored in a box labelled something like "power/motor board components 2017" in the [[Broomcupboard]].

Assembly

Board assembly was divided into the following stages:

  • Application of solder paste to the board's pads
  • Automatic placement of some SMD components using the pick-and-place machine
  • Hand placement of the remaining components
  • Reflow oven
  • Mounting of press-fit connectors (power board only)
  • Through-hole soldering

The pick-and-place machine and reflow oven are located in the electronics makerspace (16/1003) at the University of Southampton. Access to and operation of this equipment was organised by laboratory staff Jeff Hooker and Simon White.