I am trying to learn to layout a PCB. I want provide VCC voltage to transistors at 1.5amps max. Using an online calculator the width I require for 0.5ounce copper board is 1mm. I oversized the PCB trace for VCC to 1.5mm. P1 is the header pin where I supply the board with VCC. Will using such a large trace post a problem when soldering ? I googled PCB design rules, and they mentioned that a thermal relief is a must for ground plane to make it easier to solder. But I can't find info if large traces will be hard to solder too.

 

the more copper the more it takes to heat

 

No, I cannot think of obvious disadvantages in the examples you have given.

 

Your calculation allows a 10°C rise in temperature at 1.5A. Using a 1.5 mm trace reduces that to 5°C. No problem. Soldering will not be a problem either until you get much bigger (e.g., a copper pour), and then yo may use "thermals" to facilitate soldering.

 

You shouldn't have any soldering problems for traces in that range (and probably quite a bit larger). Planes are very effective at dispersing heat while tracks are much less so.

 

You have the room. Little doglegs like you did at Q4 for C7 and C8 would make the board more easy to repair if you lifted a trace.

 

It is good practice to not have sharp places like the blue track going to P4. If yo have to join a track, add a round pad so there is a smoother join. And avoid right angle track changes, use a "dog leg" as keepitsimplestupid says above.
Leaving the max amount of copper on the board is not a bad idea. I have had to repair too many boards that have tiny, thin tracks and pads. If you have room, make the resistor and other component pads big. That does make it less likely to lift when repairing the board. And have the holes an easy fir for the leads, not tight, for the same reason.

 

It is good practice to not have sharp places like the blue track going to P4.

I have seen this before but it is never explained. Can you explain why this is, please?

 

Two reasons I have seen:
1) At very high frequencies is is supposed to have a bad effect. Hard to demonstrate. See: http://www.ti.com/lit/an/scaa082/scaa082.pdf (page 14) and here: https://www.montrosecompliance.com/wp-content/uploads/2014/09/corners-Japan.pdf
2) From a mechanical perspective, it is thought that sharp "points" or corners may lift more easily from the PCB or trap etchant in the corner that might lead to later corrosion.

Based on the Montrose studies and personal experience with homemade boards (corrosion), I think that recommendation is on the way to being urban myth -- at least at the frequencies I use.

As for the recommendation to use a circular pad to solve the problem, a narrow trace meeting a larger circle produces almost a right angle. I have seen triangles added, which doesn't have that problem.

 

You will not have any additional efforts in soldering to the board because of trace width. Lead free solder will give many more problems because it is not nearly as good, and because it takes a higher temperature. Of course this assertion is based on the soldering process being satisfactory to begin with.

 

@AlbertHall Sharp points will act like an antenna. Long antennas handle lower frequencies while shorter antennas are more optimized for high frequencies. The shorter the antenna the higher the frequency. So a sharp corner or point can act like an antenna. As for sharp corners, going back to the steel industry, they can act as stress risers and create points more likely to fracture. In the industry, on heavy sheet steel, an edge with a pit either had to be filled then ground smooth or, depending on the joint, could just be ground out. Sweeping surfaces are less likely to fracture than sharp corners and edges.

Transferring that to PCB traces, a 90˚ corner versus a 45˚ corner, both are potential fracture points but the 90 has a higher susceptibility to fracturing during heat expansion cycles. And as @jpanhalt has said, sharp corners are easier to lift.

 

I have seen this before but it is never explained. Can you explain why this is, please?

There are both mechanical and electrical factors involved. The electrical factors only come into play at frequencies in which the wavelengths start becoming comparable to the feature sizes involved. Any change in geometry produces a change in characteristic impedance which results in reflections. Making geometry changes smoother reduces the problem. But at the frequencies and SNR values that most hobbyists work with, the impact is negligible.

 

One think that is often overlooked it the apearance of the PCB. I try to make the boards I design look good. 45 degree bends seem better I think.
I'm put my name on all the boards I have designed and a few have quite a number in use. One in particulay, a Mag Flow meter, has quite a few thousand installed, so I want to be proud of them, their operation and looks.

 

One think that is often overlooked it the apearance of the PCB. I try to make the boards I design look good. 45 degree bends seem better I think.
I'm put my name on all the boards I have designed and a few have quite a number in use. One in particulay, a Mag Flow meter, has quite a few thousand installed, so I want to be proud of them, their operation and looks.

+1

There's a reason they call it "artwork". Take pride in it.

If I have to trade looks for performance, I'll do it (I believe in function over form in almost all situations). But the beautiful reality is that there is seldom a need to make that tradeoff -- quite the opposite, beautifully crafted workmanship usually performs better.

 

beautifully crafted workmanship usually performs better.

And a fresh coat of wax makes a car drive better.

 

And a fresh coat of wax makes a car drive better.

Actually... it may.

Pilots flying out of short, high altitude runways with obstructions are known to spend the afternoon cleaning and polishing the aircraft in order to make it as smooth as possible. Whether or not the slight decrease in drag and slight increase in lift has ever made the difference between making it out or not I have no idea, but over the decades there have certainly been enough close calls that it's not completely unreasonable to surmise that it's happened at least once. On a more mundane level, however, pilots that have monitored it closely over many years claim that there is more than sufficient improvement in fuel burn to more than pay for the wax and other supplies, even ignoring that it also makes the aircraft last longer by reducing corrosion. Plus, the slight lowering in fuel burn may well have made the difference in the occasional instance of fuel exhaustion by having made it just far enough to get to a safe landing -- but pilots that run out of fuel are seldom pilots that will be found waxing their aircraft.

 

Plus, the slight lowering in fuel burn may well have made the difference in the occasional instance of fuel exhaustion by having made it just far enough to get to a safe landing -- but pilots that run out of fuel are seldom pilots that will be found waxing their aircraft.

I'd feel a lot safer with a pilot who spent time staying proficient rather than polishing the bottom of his airplane.

 

Sailors wax the hulls of their boats before racing.

 

Pilots flying out of short, high altitude runways with obstructions are known to spend the afternoon cleaning and polishing the aircraft in order to make it as smooth as possible.

Actually there is tons of truth to this. A clean surface has better laminar flow than a rough, dirty surface. The boundary layer of air will stick better to a waxed surface than it will to a dusty surface, and yes, they will increase lift. Since my comment was directed towards automobiles, the thought is that the difference is probably so slight at those slower speeds that one would never know it. But for some reason it just feels like it drives better.

I once built a supercharger for my minibike. It ran. We SWEAR it was faster, but those little Briggs & Scrapiron motors were good at most for about 3500 RPM. Like I said, it ran. But was it TRULY faster? Maybe. Maybe not. But we SWEAR it was. Never performed any scientific tests to see if it had better acceleration or higher speed, we were just too busy having fun with it.

What was this thread about again ? ? ? OH YEAH! PCB Traces, sharp corners and oversize. I think it's already been answered though.

 

I once built a supercharger for my minibike. It ran. We SWEAR it was faster, but those little Briggs & Scrapiron motors were good at most for about 3500 RPM.

There was once a letter in 'Bike' magazine praising a previous article on a new exhaust system. The letter described how this exhaust had increased the top speed of the bike with no increase of engine RPM. The editor's reply was that this is the first time they'd heard of an exhaust system changing the gear ratio.