From 0360748b6ed89b7311a502ad573e78ce84843fc1 Mon Sep 17 00:00:00 2001 From: Nicolas Schodet Date: Fri, 24 Aug 2007 14:06:44 +0200 Subject: Added PCB design document. --- tools/quality/elec/pcb.txt | 152 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 152 insertions(+) create mode 100644 tools/quality/elec/pcb.txt (limited to 'tools') diff --git a/tools/quality/elec/pcb.txt b/tools/quality/elec/pcb.txt new file mode 100644 index 00000000..151dce59 --- /dev/null +++ b/tools/quality/elec/pcb.txt @@ -0,0 +1,152 @@ +============================== + Printed Circuit Board Design +============================== +:Author: Ni + +This document should gather any useful information for PCB [1]_ design at APBTeam. + +.. [1] Printed Circuit Board + +Standards +========= + +Software +-------- + +The software used currently for any PCB is Eagle from CadSoft. CadSoft +distributes a freeware version running under Linux or MS Windows for +non-profit usage, limited by the PCB size and the number of usable layers. + +In the future, we may switch to a free software solution: KiCad. But Eagle +offers several advantages: all previously designed libraries and boards were +using Eagle and Olimex takes directly Eagle files. + +Manufacturer +------------ + +Our boards should be suitable to be manufactured by Olimex, a low-cost +prototype board manufacturer. They make double sided Europe size boards for +about 30 euros, with solder mask, metallised holes and one silk screen. + +PCB Size +-------- + +Most boards are a division of a Europe format board. Europe is 10x16cm, 1/2 +Europe is 8x10cm and 1/4 Europe is 5x8cm. Actually, a margin must be +subtracted for panelization. + +Some components have a standard position. This include mounting holes and +side connectors. + +- mounting holes: MOUNT-HOLE3.3 in the holes library: + + - at (0.15 0.15) and (0.15 2.925) for 1/4 Europe, + - at (0.15 0.15), (0.15 2.925), (3.65 0.15) and (3.65 2.925) for 1/2 Europe. + +For exact dimensions and positions, please see the asserv board for 1/4 Europe +and the puiss board for 1/2 Europe. + +Connectors +---------- + +Here is the list of used connectors: + +- HE10 for signals, usually 10 pins +- HE10, 6 pins for I2C +- pin heads for servomotors +- HE14 (TBC) for miscellaneous sensors and low pin number signals +- HE14 (TBC) for digital board power +- Phoenix 381 connectors for power connections +- Micromatch SMD connectors for small size connections + +As a rule of thumb, use the pin number 1 for ground and pin number 2 for +positive voltage. + +Check List +========== + +For board manufactured at Olimex use their DRC file for auto-routing and +Design Rules Check! + +As the same errors occurs again and again, here is a list of items you should +check when you design a PCB: + +Power connections + Are all the components powered? Is there a power connector? + +Decoupling + Use decoupling capacitors on the power and near each components. + Capacitors should be the nearest possible of the components. Do not put + to much decoupling or the board will drain to much current when switched + on. + +Text size + Check text size in order to be able to read it. For Olimex: vectorial + font, 70 mils, 15%. + +Text on each layer + There should be text on each circuit layer (top and bottom). This makes + it easy to known if the layer is in the right direction. This is also a + Olimex requirement. + +Board size + Has the board the right size? Is there extra margin for panelization? + +Mounting holes + Check holes types and positions. + +Connectors + Are the connector near enough of the board edge? Some connectors, like + Phoenix ones, use space lower than the board, if the connector is to far + from the edge, it will not be possible to plug it. + + Are they at the right position ? + +Track size + Use the largest possible tracks. Use larger tracks for power. For high + power tracks, the solder mask can be removed on a particular region. + +Component side + Are the components on the right side? This is particularly hard to see + for through hole mounted components. + +Component placement + Check than no component override each other. Check that it is possible to + solder them without a master level of dexterity. + + For board without metallised holes, use restrict layer to forbid + connection where soldering would be very hard (for example, it is not a + nice thing to try to solder a track going under a HE10 connector). + + Always place component on the grid. + +Logistic + Check that all components are available with the right size and package. + This is particularly true for capacitors. + +Serial ports + Double check pinout! Should TX and RX be inverted? This one is for you + Pierre! + +Protection + Use pull-up or down resistors or shorts-protection resistors. + +Optocouplers + Use them to separate command and power. + +ERC and DRC + Use Eagle tools to check the board. For boards manufactured by Olimex, + use the file they provide for DRC. + +Drills + Limit the use of different drill size and use standard drill size. This + increase the board cost. Be careful, the metalization will reduce the + hole size! + +Routing + Prefer auto-routing as this is easier to make modifications. + +Silk screen + Print useful information on it. Do not forget to run the Olimex provided + script to fix it right before sending file to them, but do not save the + result in the repository as this make editing harder. -- cgit v1.2.3