I am required to design a PCB in Allegro for this circuit:
The problem is that our teacher believes that we have too much free time so our introduction into Allegro was close to none. I have searched the internet and found some videos and documents regarding my issues but I can't be certain that everything is actually ok! Furthermore I have two problems I couldn't solve at all:
- As seen, there is a potentiometer in the design. I found a PCB footprint, downloaded it (it actually had a tutorial video attached and followed it) but I got this error:
- I was told that I am required to put two fiducial markers on my PCB but I couldn't find the PCB editor everyone apparently has when using OrCAD!
For more information this is what I came up with:
and these are all the instructions that I have received:
For SMT & PCB technology, the circuit will be made in the form of an electronic module whose interconnect structure (PCB) will comply with the following design requirements:
- PCB dimensions: 40mm x 40mm;
- Material FR4, double layer/ copper foil thickness 18 μm, plate thickness 1.5 mm;
- All components will be placed on the upper side of the plate, TOP;
- Passive components SMD chip 0805;
- Only bipolar transistors and TEC-MOS can be used in SMD capsules (SOT 23, DPAK). TEC-J transistors can only be used if the need is justified them.
- Test points: circular, maximum 5 – justified by the test plan;
- The origin (coordinate point (0,0)) will be placed in the lower-left corner of the printed wiring, so all project elements will have positive coordinates;
- Against the edge of the plate, a clearance of 1 mm will be kept; they won't be components placed here, routes, texts, etc.;
- The board will be provided with 2 global fiducial markers on the TOP layer, at a distance of 200 mil from the edge of the board, place conveniently; these markers will also exist on the layer Solder Paste Top (overlaid on TOP); will be used at the time of alignment template with the plate. The fiducial mark will be a circle with a minimum diameter of 1mm on the layer respectively, located in a circular space with a minimum diameter twice that of the inner circle, in which there will be nothing on any layer;
- Greater attention will be paid to the Inscription Mask (Silk Screen) layer; this must not be found on component pads;
- A new non-electric, MECHANICAL layer will be generated. It will contain: the outline of the board, the drilling drawing ("drill drawing") and the drilling table ("drill chart/table", "drill legend"), a cross-section through the designed printed circuit ("layer stack-up") and the mechanical information required for PCB manufacturing; 2 | 5
- The gauge dimensions/plate dimensions must not be found on the electrical layer TOP; these, if any, will be placed on a mechanical non-electrical layer;
- The plate will be provided with the identification elements of the designer (name, surname, group, PDCE I 2022-2023).
The following widths are given for the interconnecting routes:
- Current of 1A - 28 mil;
- Current of hundreds of mA - 22 mil;
- Signal - 18 mil. The spacing, in all cases, will be 12 mil. The through holes for signals (vias) will have a diameter of 0.4 mm.
Gerber files - standard 274X and Excellon file must contain the following information:
- Board outline;
- TOP electric layer;
- Electric layer BOTTOM;
- Non-electric layer Printing mask (Silk Screen Top);
- Non-electric layers Protective mask (Solder Mask Top and Bottom);
- Non-electric Layer Template (Solder Paste Top);
- Aperture list and drilling file.
NOTE! Mandatory design requirements:
a. PCB dimensions: 40mm x 40mm;
b. Material FR4, double layer;
c. The origin (coordinate point (0,0)) will be placed in the lower-left corner of the printed wiring board, so all elements of the project will have coordinates positive;
d. The size of the routes and their spacing in accordance with the mentioned specifications.
Design requirements aim at knowledge, compliance and application of IPC standards from the electronics industry in the realization of the electronic module for Project 1, as it follows:
IPC-2221A, "Generic Standard on Printed Board Design", regarding route routing conductors, conductor spacing, pad sizes for SMD components, presence of marking and orientation of symbols, provision of test points and provision of bridges thermal (where applicable);
IPC-7527, "Requirements for Solder Paste Printing", for the deposition operation a contact pastes;
IPC-A-610, "Acceptability of Electronic Assemblies", for validating the operations of component placement and actual contact for module acceptability assembled electronics.
I would like at least to understand what I am doing instead of just messing around and hoping I found something close to a solution!
