Maker Pro
Maker Pro

Surface mount, why are parts so small?

R

Raveninghorde

Jan 1, 1970
0
I've been working on a sepic converter. There are some great parts
out there in tiny packages.

Then, for example, I find the fets need a square inch of 2oz copper
(to achieve 78C/W), to get the heat out. And the diodes, and the sense
resistors, and ... A square inch, I can fit another 4 inductors in
that space.

What is the point of making parts that small? I'm looking at a TO220
fet now because it needs less pcb space than a superSOT-6 device.
 
E

Eeyore

Jan 1, 1970
0
Raveninghorde said:
I've been working on a sepic converter. There are some great parts
out there in tiny packages.

Then, for example, I find the fets need a square inch of 2oz copper
(to achieve 78C/W), to get the heat out.

Pleased to hear you bothered to work it out.

And the diodes, and the sense
resistors, and ... A square inch, I can fit another 4 inductors in
that space.

What is the point of making parts that small? I'm looking at a TO220
fet now because it needs less pcb space than a superSOT-6 device.

Flavour of the month ?

Graham
 
R

Raveninghorde

Jan 1, 1970
0
Pleased to hear you bothered to work it out.

I was an idiot. I only checked after I found the fet got hot.:(

I'm only after 1A at 17V. But from a 10V input I squared R caught me.
It's a 0.055R fet. But of course that rises as the fet gets hot enough
to melt (lead free) solder.
 
D

David L. Jones

Jan 1, 1970
0
Raveninghorde said:
I've been working on a sepic converter. There are some great parts
out there in tiny packages.

Then, for example, I find the fets need a square inch of 2oz copper
(to achieve 78C/W), to get the heat out. And the diodes, and the sense
resistors, and ... A square inch, I can fit another 4 inductors in
that space.

What is the point of making parts that small?

It's because almost all commercial boards are machine assembled these days,
so small size is not only not a problem, it's a major benefit in apps were
every square mm counts, and that's more common than you'd think. The
majority of the market want small parts, so that's the direction the market
heads.

Dave.
 
E

Eeyore

Jan 1, 1970
0
David L. Jones said:
It's because almost all commercial boards are machine assembled these days,
so small size is not only not a problem, it's a major benefit in apps were
every square mm counts, and that's more common than you'd think. The
majority of the market want small parts, so that's the direction the market
heads.

As long as it's low power. Doing a trial exercise for a pro-audio product we
had to be careful with resistor ratings since they could conceivably fail in
normal use due to dissipation.

Also, whatever they use for those SMT resistors isn't as quiet as leaded
components.

Graham
 
R

Rene Tschaggelar

Jan 1, 1970
0
How about two or three of the S6 FETs in parallel ?

Rene
 
R

Rich Grise

Jan 1, 1970
0
Also, whatever they use for those SMT resistors isn't as quiet as leaded
components.

Does anyone else find it a tad irksome that leaded, pronounced "leeded",
"having leads (wires)", is spelled the same as leaded, pronounced
"ledded", meaning, "having lead (metal) added"?

Thanks,
Rich
 
Top