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Layout mistakes and suggestions for improvement

Hamidab , 01-31-2023, 04:33 AM

The attached file shows layers of a four layer PCB (un-isolated) which is for switching ON and OFF 6 loads (loads are connected to 230VAC) as a practice of PCB layout in Altium PCB Design tools.
I would appreciate if the mistakes about the layout of this board are pointed out and welcome any suggestions for its layout improvement.

Thank you and regards.
qdrives , 01-31-2023, 02:24 PM
Creepage and clearance? IPC, IEC 60664 (http://i.stack.imgur.com/9RKgF.jpg) or even IEC 60335, UL/IEC(60)950, etc.
Hole in hole for the heat sink should not be done
Heat sink connected to PE?
Do not go across pin to pin (U1?)
You want some thermal reliefs on the Line connections.

Remove the 3D next time and add some transparency. Makes looking at it a bit easier.
Hamidab , 02-02-2023, 06:21 AM
Hello qdrives,

Thanks for your points.

1- The voltages on the board are 3V DC for the digital parts and 10V DC for analog parts and therefore I think the creepage is not an issue for these level of voltages. Am I correct on this?
I have also heard that protective paint can be applied on the board to avoid creepage problem. How far is this idea correct?

The Neutral of 230V AC is connected to A1 and A2 of each triac (act as switches). The Neutral and Line tracks are separated as much as possible (at least 3.5mm).
The separation of A1 and A2 of the triacs depends on the component footprint and I wonder what the creepage rules are for this situation.

2- Since there are two options for the heatsink, I made a footprint that can be used for both heatsinks. This is the reason for hole in hole. Is there any other way to have the same footprint for both heatsink but without creating the problem of hole to hole?

3- The heat sinks are connected to the back of the their triacs which are connected to pin2 of triacs. Pin2 of the triacs then go to Neutral. Neutral is connected to the AGND of the board which is not PE (Protective Earth).

4- Please see the attached fig for pin to pin connection in U1 and let me know if I understood your point about pin to pin connection?

5- I made thermal reliefs as you said, see the attached fig., but I wonder if the thermal reliefs reduce the current limit that can be passed via power tracks?

6- The transparency is added for 3D bodies as in the attached fig.
qdrives , 02-02-2023, 01:48 PM
1) Both Line and Neutral are primary side. I assume that the DC part are secondary?

Do note that in most cases, neutral CANNOT be considered as 0V, so consider line and neutral to be swapped. If I remember correctly, only large fixed installations may consider Line and Neutral to be connected (applied) correctly.

Old rules in Europe: 3mm when PE is used (class I device) and 6mm for double isolation (class II)

Perhaps these will also help:
https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/188/Clearance-and-creepage_5F00_UL_2D00_60950_5F00_IEC_2D00_60950.pd f

Question is also:
- Which country, countries or continents
- Type of application: residential, (light) industrial, medical, fixed or portable, machine / appliance / IT / etc.

2) Talk to a fabricator on this topic and add a note in the documentation (that they receive as well).

3) So it is hot (voltage wise) ! There are ways to insulate it.

4) Yes, that is correct.

5) Yes, thermal relief will reduce current. But the question is - will it be to much?
Or perhaps even a better question is - how much? This answer if often -- very little.

6) I did not mean transparency for the 3D model, but transparency on the copper layers. 3D layer can be hidden completely.
Hamidab , 02-03-2023, 03:40 AM
Hello qdrives,

Thank you for your comments.

1- Please see the attached fig. Line and Neutral are connected to the board and to the DC power supply. The fig shows 5V DC power supply, but in this case 12V DC power supply and then it is connected to a regulator to generate 3V DC. The GND of the power supply is connected to Neutral in order to be able to use the triac as switch for the load. What are the problems about this connection?
2- type of application : Appliance /domestic use.
3- Location: Europe
The board is covered with a PVC container and is isolated from the user by this container. <Are there any specific requirements on this method of board and isolation?
4- The maximum power of the load is 1500W for few minutes.
qdrives , 02-03-2023, 02:58 PM
Where do all the connectors in the end go to?
Are the power supplies within the PVC container?
The programming connector is to Gnd and goes to a programmer and PC...
All kinds of button, switches, LEDs, etc have to be considered (with clearance).

Application --> IEC 60335, 1500W in enough to cause problems --> safety --> IEC 60730
Europe --> LVD (Low Voltage Directive)

LVD is free, IEC standards are not, but I would highly recommend purchasing it.

Have you though on using opto-couplers to drive the triacs? They allow you to keep everything safe!
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