Triac track width and clearance advices?

Hallet wrote:

Hi,

 

Im making the layout for a PCB that uses a triac in TO-220 package.

The maximum current in the triac (BTA312Y) is 8 Amp. and the copper

thickness 35m (1 oz/ft^2). What track width would you recommend? Ive

seen calculators on the Internet but they ask the allowable

temperature rise and I dont know what value I can choose. On the

other hand, Ive seen that IPC recommends 220mil for 8 Amp., 10C rise

and 1oz/ft^2 Cu but its very big?

Well, 8A is a lot of current, so it will require a pretty fat trace.  For

temperature rise, what can you tolerate?  If you have a "nice" ambient

environment of, say, 25C, then you might consider a greater PCB trace

temperature rise.  If you allow a 30C temperature rise, then the PCB tracks

near your TRIAC might rise to a temperature of 25C + 30C = 55C.  If your

TRIAC is mounted to the PCB, then its case may also be at 55C (though you

probably have a big heat sink), so you'll have to consider that in your

calculation of junction temperature in the TRIAC.

At a 30C temperature rise, you only need about a 100mil track to carry 8A.

If you can use 2oz copper instead of 1oz, then you can halve the track width

again.

I would use as much copper as possible for conducting the current.  I

generally use polygons to make use of all available space for carrying big

currents -- more copper is better.

What value do you use for track clearance for 220V mains voltages? Ive

seen 0.75mm

(http://www.electronics-project-design.com/PCB-Design.html ) for

coated board. But here

(http://www.smpspowersupply.com/ipc2221pcbclearance.html ) the values

are not the same and I dont know what to use? Is bare board for PCB

without parts on it? So do I have to use assembly and external

components leads, uncoated if : the board has a solder resist mask,

is populated and if there is no coating on component leads? Is the

clearance also needed between the components pads (external diameter

to external diameter)? If so, is it possible with a standard TO-220

package?

Sorry, little experience with 220V clearance requirements.  Maybe somebody

else will comment?

--

Bert Menkveld

Hallet wrote:

Hi,

 

Im making the layout for a PCB that uses a triac in TO-220 package.

The maximum current in the triac (BTA312Y) is 8 Amp. and the copper

thickness 35m (1 oz/ft^2). What track width would you recommend? Ive

seen calculators on the Internet but they ask the allowable

temperature rise and I dont know what value I can choose. On the

other hand, Ive seen that IPC recommends 220mil for 8 Amp., 10C rise

and 1oz/ft^2 Cu but its very big?

Well, 8A is a lot of current, so it will require a pretty fat trace.  For

temperature rise, what can you tolerate?  If you have a "nice" ambient

environment of, say, 25C, then you might consider a greater PCB trace

temperature rise.  If you allow a 30C temperature rise, then the PCB tracks

near your TRIAC might rise to a temperature of 25C + 30C = 55C.  If your

TRIAC is mounted to the PCB, then its case may also be at 55C (though you

probably have a big heat sink), so you'll have to consider that in your

calculation of junction temperature in the TRIAC.

At a 30C temperature rise, you only need about a 100mil track to carry 8A.

If you can use 2oz copper instead of 1oz, then you can halve the track width

again.

I would use as much copper as possible for conducting the current.  I

generally use polygons to make use of all available space for carrying big

currents -- more copper is better.

What value do you use for track clearance for 220V mains voltages? Ive

seen 0.75mm

(http://www.electronics-project-design.com/PCB-Design.html ) for

coated board. But here

(http://www.smpspowersupply.com/ipc2221pcbclearance.html ) the values

are not the same and I dont know what to use? Is bare board for PCB

without parts on it? So do I have to use assembly and external

components leads, uncoated if : the board has a solder resist mask,

is populated and if there is no coating on component leads? Is the

clearance also needed between the components pads (external diameter

to external diameter)? If so, is it possible with a standard TO-220

package?

Sorry, little experience with 220V clearance requirements.  Maybe somebody

else will comment?

--

Bert Menkveld