University of Leicester
PLUME
Ref: PLM-MEC-PcbInterface-801-1
Date: 31/01/2009
CubeSat Subsystem Mechanical Interface Document
D.S.W. Gray
Date
Updated Reference Number
change
31/01/2009
PLM-MEC-PcbInterface-801-1
first version issued
All subsystems requiring fabrication of printed circuit boards (PCBs), must comply with the
mechanical specifications laid out in this document. The document gives PCB dimensions,
fixing positions and the cubesat kit bus connector position for stacking PCBs inside the
cubesat kit structure.
ADCS and PAY will be fabricating their own board. OBDH, COMS and PSU have complete
flight hardware, except connectors to external mountings.
Mass
Each PCB has a mass of approximately 0.026kg excluding the cubesat kit bus connector
and other components. PCBs are made of FR4 (Flame Retardant 4). Specifications are
available from wikipedia [1].
The mass of the connectors in total is 0.039kg. The mass of the 4 threaded rods and midplane standoff (that can be purchased from Pumkin Ltd [2], or manufactured in the SRC) is
0.019kg.
The mass of each cubesat kit bus connector, and the connector’s extension block is
currently unknown.
PCB Fixing Method
The Aluminium cubesat kit structure is comprised of 6 sides bolted together. The PCBs are
held in position by 4 steel threaded rods screwed into the inside structure at the corners of
the ‘bottom’ side. This side contains the launch switch and springs, and is mounted to the
Page 1 of 4
University of Leicester
PLUME
Ref: PLM-MEC-PcbInterface-801-1
Date: 31/01/2009
OBDH board supplied with the kit. Aluminium spacing tubes of length 15mm or 25mm
separate the PCBs in the stack. The stack is fixed by tightening at the top with the midplane standoff. This screws into the ‘vertical’ sides of the cubesat structure.
The OBDH board is currently held in position against the ‘bottom’ side by 4 screws. These
are to be released and replaced with the threaded rods individually (to avoid introducing new
stresses on the board (T. Stevenson)). A PC/104 style connector space will be added to the
cubesat kit bus connector, and 25mm Aluminium tube spacers used to make space between
the OBDH board and next board in the stack. This is so that the transceiver can be mounted
on the OBDH board.
PCB Shape
Based on current hardware, available computer models and technical drawings the 4
threaded rods are not in symmetrical geometric positions, and the PCBs’ shapes are not
perfect squares. There are 4 cut outs required for compatibility with the cubesat kit
structure.
The shape of the PCBs will be given in reference to the centre of the threaded rod that is
next to both the cubesat kit bus connector, and the launch switch on the OBDH board. This
position is marked on drawings by a red circle with cross hairs.
It is highly advisable that non-flight PCB mock-ups are made to ensure that the mechanical
specifications can be met before construction of flight hardware begins.
Cubesat Kit Bus Connector Position
The PC/104 style connector is also specified with respect to the centre of the reference rod.
The height of the connectors must be considered, pending the decision on a transceiver.
The height of the connector on the flight board, with the adapter to make space for the
transceiver is 19.56mm (T. Stevenson). The height of a standard connector is 10mm.
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University of Leicester
Fig 3.
PLUME
Ref: PLM-MEC-PcbInterface-801-1
Date: 31/01/2009
CAD drawing of a skeletized cubesat kit including the 4 corner rods and Aluminium tubes,
mid-plane standoff and PCB cutouts. [2].
Fig. 4 Positions of centres of structure rods, PCB dimensions and Cubesat kit bus connector, with
respect to the centre of the lower right rod. All dimensions are in millimetres. Blue numbers indicate
bus positioning. Red numbers indicate rod positions. Green numbers indicate x axis positions.
Orange numbers indicate y axis positions.
References
Page 3 of 4
University of Leicester
[1]
[2]
PLUME
Ref: PLM-MEC-PcbInterface-801-1
Date: 31/01/2009
http://en.wikipedia.org/wiki/FR4
http://www.cubesatkit.com/docs/datasheet/DS_CSK_Midplane_Standoff_71100331-B.pdf
All websites viewed 31.01.2009.
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