Hi everyone,
I am refurbing/fixing an issue 2 board (separate post coming) and I was wondering whether in lieu of soldering the relatively-fragile ULA directly to the PCB a turned pin socket provided any significant thermal benefit as a workable compromise.
Has anyone done any work on IC socket thermals? I've found plenty of online resources about the characteristics of DIP IC packaging (ceramic, epoxy etc.), but not anything (so far) on sockets.
Thanks
Turned pin sockets - thermal benefit?
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linker3000
- Drutt
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Re: Turned pin sockets - thermal benefit?
Sockets don't bring any thermal advantage because the heat is generated in the centre of the package, but the pins are linked to the silicon chip using very thin wires, hence no thermal advantage can be significant through the pins and sockets.
What you can do, is attach an aluminium (metal) dissipator on top of the chip, using good thermal paste to facilitate the heat transfer between the package and the metallic dissipator. However, you need to find a low profile one, or it won't fit inside the case.
On another note, if you are concerned with temperature, you should replace the Linear Regulator (7805), and use a switchable one (Traco Power TSR1, https://uk.rs-online.com/web/p/switchin ... s/6664379/).
Alternatively, if you don't want to open the machine or de-solder the 7805, you can also swap the external power brick with a switchable one, while keeping the 7805 inside, since you can use a lower voltage (minimum 7.5V) and the Linear regular will still do it's job, but will dissipate a lot less heat, since it doesn't need to convert such a large difference in voltage (around 11V to 14v, that the original power bricks can generate) into 5V.
What you can do, is attach an aluminium (metal) dissipator on top of the chip, using good thermal paste to facilitate the heat transfer between the package and the metallic dissipator. However, you need to find a low profile one, or it won't fit inside the case.
On another note, if you are concerned with temperature, you should replace the Linear Regulator (7805), and use a switchable one (Traco Power TSR1, https://uk.rs-online.com/web/p/switchin ... s/6664379/).
Alternatively, if you don't want to open the machine or de-solder the 7805, you can also swap the external power brick with a switchable one, while keeping the 7805 inside, since you can use a lower voltage (minimum 7.5V) and the Linear regular will still do it's job, but will dissipate a lot less heat, since it doesn't need to convert such a large difference in voltage (around 11V to 14v, that the original power bricks can generate) into 5V.
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1024MAK
- Bugaboo
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- Location: Sunny Somerset in the U.K. in Europe
Re: Turned pin sockets - thermal benefit?
The ULA is designed to run hot. On the actual chip die, around all four outside edges are multiple series pass voltage regulators. All these generate heat, as well as the actual digital circuitry.
Plastic packages are not very good at conducting heat. And as RMartins says, the thin bond wires limit the amount of heat that can flow from the chip to the legs of the chip (although some 8 pin DIP chips such as regulators and power amplifiers do use the pins to help with removing heat).
A semiconductor chip can run as hot as 100°C to 125°C
At various times, Sinclair used sockets for the ULA, so using a turned pin type is okay.
If the board is fitted in a rubber key case, due to the poor ventilation, fitting a heatsink does not do much good, as the air trapped in the case will heat up and then the heatsink does not help very much.
But if you want to fit a heatsink to a ULA in a + case (or other type), that’s fine.
When using a heatsink, use a thin smear of heatsink paste / silicone grease / heatsink compound. The idea is that the paste fills in any holes or unevenness, the paste being a better heat conductor than any trapped air.
Mark
Plastic packages are not very good at conducting heat. And as RMartins says, the thin bond wires limit the amount of heat that can flow from the chip to the legs of the chip (although some 8 pin DIP chips such as regulators and power amplifiers do use the pins to help with removing heat).
A semiconductor chip can run as hot as 100°C to 125°C
At various times, Sinclair used sockets for the ULA, so using a turned pin type is okay.
If the board is fitted in a rubber key case, due to the poor ventilation, fitting a heatsink does not do much good, as the air trapped in the case will heat up and then the heatsink does not help very much.
But if you want to fit a heatsink to a ULA in a + case (or other type), that’s fine.
When using a heatsink, use a thin smear of heatsink paste / silicone grease / heatsink compound. The idea is that the paste fills in any holes or unevenness, the paste being a better heat conductor than any trapped air.
Mark
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Looking forward to summer later in the year.
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Firefox
Re: Turned pin sockets - thermal benefit?
Well, since both sides of the die are in contact with the epoxy of the package, and a large part of the leadframe is also immersed in the epoxy, a fair proportion of the waste heat is transferred to the leadframe as well as being radiated away directly from the package.
So, you could argue that a dual-wipe contact socket would allow more heat to be conducted into the PCB traces than a turned-pin socket because of the larger contact area per pin.
As Mark says, though, chips are built to run within a certain temperature range, and there's little point in worrying unless it gets hotter than it's designed for.
So, you could argue that a dual-wipe contact socket would allow more heat to be conducted into the PCB traces than a turned-pin socket because of the larger contact area per pin.
As Mark says, though, chips are built to run within a certain temperature range, and there's little point in worrying unless it gets hotter than it's designed for.