Lead spacing for through hole resistor

[CeeRox]

Hi!

What lead spacing should I use on the PCB for through hole mounted
resistors..?
Is there any generall standard for this..I didn't find much info in the
IPC2220...

/CeeRox

 

[Pooh Bear]

Hi!

What lead spacing should I use on the PCB for through hole mounted
resistors..?

What power rating / body size ?

Is there any generall standard for this.

There's accepted practice.

I didn't find much info in the IPC2220...

IPC2220 ? Hmm. hadn't heard of that before.

Graham

 

[Noway2]

Hi!

What lead spacing should I use on the PCB for through hole mounted
resistors..?
Is there any generall standard for this..I didn't find much info in the
IPC2220...

/CeeRox

It depends on the package body size. Search some manufacturers
websites and datahseets and see if you can find a suggested footprint
or land pattern.

For through hole resistors, I usually try to keep the spacing to a
..100" increment (.200", .300", etc) depending the size. I try to
maintain some measure of a grid spacing and alignment to keep things
neat, though this is sometimes difficult.

Another consideration is I try to standardize the hole sizes as much as
possible because the more different hole sizes you have means more
drill changes are needed which equates to more cost.

 

[Leon]

Hi!

What lead spacing should I use on the PCB for through hole mounted
resistors..?
Is there any generall standard for this..I didn't find much info in the
IPC2220...

/CeeRox

IPC deals mainly with SMDs. I use 0.4" for 1/4 W resistors, I think
that most people do.

Leon

 

[Spehro Pefhany]

IPC deals mainly with SMDs. I use 0.4" for 1/4 W resistors, I think
that most people do.

Leon

Or maybe 10mm.


Best regards,
Spehro Pefhany

 

[martin griffith]

Hi!

What lead spacing should I use on the PCB for through hole mounted
resistors..?
Is there any generall standard for this..I didn't find much info in the
IPC2220...

/CeeRox

I'd allow approx 2mm per lead extra over the body length for the lead
forming machine. see data sheet here
http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=150396&N=401


martin

 

[Wayne Lundberg]

..20 is the standard. You can lay them down and bend the leads to fit
whatever space available, or you can bend one lead 180 degrees and insert
both leads within the .100 or .200 spacing on the PC board as long as you
have height space.

 

[Pooh Bear]

.20 is the standard.

It is ? Most ppl use 0.4" IME or 0.3" for 1/8W to save space.

You can lay them down and bend the leads to fit
whatever space available, or you can bend one lead 180 degrees and insert
both leads within the .100 or .200 spacing on the PC board as long as you
have height space.

I wouldn't recommend vertical mounting.

Graham

 

[Roy L. Fuchs]

It is ? Most ppl use 0.4" IME or 0.3" for 1/8W to save space.


I wouldn't recommend vertical mounting.

Graham

That depends on whether it is a fixed or mobile application.

If mobile, it is still OK if the item gets encapsulated or
conformally coated as well.

They actually dissipate their heat better as well.

The silk screen is nicer too. A simple circle with a little dash
pointing toward the other hole connected to the circle perimeter.

The ONLY problem I can think of that vertical axial leaded resistor
mounting has is in automated production cycles. It typically causes a
few insertion failures or solder cycle failures or a few sorts.

There is absolutely nothing wrong with the practice from an
electrical POV, however.

 

[Leon]

It is ? Most ppl use 0.4" IME or 0.3" for 1/8W to save space.


I wouldn't recommend vertical mounting.

I've had to use it on occasion, to get a board to fit a specified
enclosure. I can't think of any reasons not to do it for hand-assembled
boards, especially for amateur radio applications which is when I have
used it.

Leon

 

[Pooh Bear]

I've had to use it on occasion, to get a board to fit a specified
enclosure. I can't think of any reasons not to do it for hand-assembled
boards, especially for amateur radio applications which is when I have
used it.

Think of the stress on the mechanical solder joint esp wrt single sided boards.

Graham

 

[Leon]

Think of the stress on the mechanical solder joint esp wrt single sided boards.

Where does the stress come from?

Leon

 

[John Fields]

That depends on whether it is a fixed or mobile application.

If mobile, it is still OK if the item gets encapsulated or
conformally coated as well.

They actually dissipate their heat better as well.

---
I don't think so. Horizontally mounted, the leads are short and
sunk to a pad/trace which helps with conducting the heat out of the
center of the resitor. Also, the entire horizontal surface is
radiating and convecting heat away from the resistor body.

Mounted vertically, only one lead is mounted close to a pad. The
other one and the body of the resistor catch the heat that's being
convected upward with the result that there's a temperature gradient
generated which will make the resistor progressively hotter as its
apex is approached. As a result, part of the resistor will be
hotter than if it were horizontally mounted.
---

The ONLY problem I can think of that vertical axial leaded resistor
mounting has is in automated production cycles. It typically causes a
few insertion failures or solder cycle failures or a few sorts.

---
See above.
---

There is absolutely nothing wrong with the practice from an
electrical POV, however.

---
If the dissipation is miniscule, I agree.

But, if the resistor is dissipating a sizable fraction of its rating
I'd be leery of mounting it vertically without getting some
temperature data.

 

[Roy L. Fuchs]

I don't think so. Horizontally mounted, the leads are short and
sunk to a pad/trace which helps with conducting the heat out of the
center of the resitor.

True, but that is via conduction. I was referring to radiated
dissipation.

Also, the entire horizontal surface is
radiating and convecting heat away from the resistor body.

So is the entire vertical surface. In fact, the horizontal surface
has a fiberglass low thermal conduction PCB which it is against that
will negate some of its radiating capacity.. even blanketing the part
and slowing the dissipation of its heat.

Cement bathtub type power resistors are mounted vertically all the
time (read quite often) for this reason, and for the reason of not
wanting to burn up said fiberglass based PCB assembly.

 

[Roy L. Fuchs]

Mounted vertically, only one lead is mounted close to a pad. The
other one and the body of the resistor catch the heat that's being
convected upward with the result that there's a temperature gradient
generated which will make the resistor progressively hotter as its
apex is approached.

IR heat radiates outward and the temp at the bottom of the ceramic
cylinder in the resistor will be a mere few degrees cooler than the
top, at best.

As a result, part of the resistor will be
hotter than if it were horizontally mounted.

Why is it then, that in practice, they are not?

Even an IR imager proves it.

For a properly designed assembly. If one actually designs near the
resistor's declared capacity, heat is going to be an issue regardless
of how the device is mounted. If one designs in the component such
that it does NOT get anywhere near it's rated upper end, it will
always be cool enough for either mounting fashion not to be a problem.

The mere difference of heat conducting down a body length wire to
the PCB connection, and it being right there at the resistor body are
very near negligible as well.

 

[Roy L. Fuchs]

If the dissipation is miniscule, I agree.

But, if the resistor is dissipating a sizable fraction of its rating
I'd be leery of mounting it vertically without getting some
temperature data.

In either vertical OR horizontal mounting (without a reasonable space
between it and the PCB), I would say that one should be leery of
either choice.

 

[Spehro Pefhany]

In either vertical OR horizontal mounting (without a reasonable space
between it and the PCB), I would say that one should be leery of
either choice.

Hundreds of millions of portable transistor radios were made with most
of the axial-lead components mounted vertically on the cheapest
paper-based phenolic boards. They were pretty reliable.


Best regards,
Spehro Pefhany

 

[Pooh Bear]

Hundreds of millions of portable transistor radios were made with most
of the axial-lead components mounted vertically on the cheapest
paper-based phenolic boards. They were pretty reliable.

That kind of stuff used resistors that had 'enamelled' leads to prevent
inadvertent shorts and a kinked lead to help relieve the mechanical joint at the
pcb.

Graham

 

[Pooh Bear]

Oh, but that high tech stuff came later. The early ones often had
plastic tubing on the leads, or nothing at all.

I've got an old BT ( actually Post Office Telecommunications ) modem somewhere that
has many of the components mounted in stress relieving cradles. Some even have a
stress relief loop on the leads !

Graham

 

[Spehro Pefhany]

That kind of stuff used resistors that had 'enamelled' leads to prevent
inadvertent shorts and a kinked lead to help relieve the mechanical joint at the
pcb.

Graham

Oh, but that high tech stuff came later. The early ones often had
plastic tubing on the leads, or nothing at all.