PCB design: Hole size for resistors, ICs, Caps, etc ??
1RFD...@mtsacvm.mtsac.edu
First of all, Thanks to everyone who answer my question on how much
current a 5 mil trace can stand. You , all, were very helpfull.
Now that i have the prototype ready, i called a PCB manufacturer to
get a quote and i run into another problem: Hole sizes !!??
The CAD program i used shows IC , and heck all of the pins for
everything, the same size , 0.035 in or 35 mils.
I checked some databooks and the IC pins for a 16 pin plastic chip
never goes below 25 mils, can i change the holes in my board to 25 mils ?
What about the size for 1/4 and 1/8 watt resistors, is 25 mils ok ?
I don't have any info on passive components :-( . Is there a document
that shows the standard hole size for everything :-) ?
one last one ...:-) ... If a book were to say that a resistor (in case
i get some info) has a max hole size of ...say ...20 mils , should
i make it a bit larger ...like 25 ??
Please reply to : 1rfd...@ibm.mtsac.edu
Thanks you.
Douglas W. Jones,201H MLH,3193350740,3193382879
by 1RFD...@MtSACvm.MtSAC.edu:
> The CAD program i used shows IC , and heck all of the pins for
> everything, the same size , 0.035 in or 35 mils.
> I checked some databooks and the IC pins for a 16 pin plastic chip
> never goes below 25 mils, can i change the holes in my board to 25 mils ?
You can, but you won't be able to get the pins in the hole! Give yourself
a few mils of clearance to get the pin in the hole and to let the solder
wick in between the plated-through hole wall and the pin. With 5 mils of
clearance, you'll get the components in in a reasonable amount of time,
and with 10 mils of clearance, you'll get the board stuffed quickly. That's
why 35 mils is the norm.
> What about the size for 1/4 and 1/8 watt resistors, is 25 mils ok ?
For most small resistors, you can use the same size you'd use for IC pins.
power diodes like the 1N400X family have fat leads, though!
> Is there a document that shows the standard hole size for everything?
A pair of calipers (vernier or micrometer) will do wonderfully! Even a
magnifying loupe and a machinist's scale graduated in 100ths of an inch
will do the job.
Doug Jones
jo...@cs.uiowa.edu
P.Bennett
> The CAD program i used shows IC , and heck all of the pins for
> everything, the same size , 0.035 in or 35 mils.
> I checked some databooks and the IC pins for a 16 pin plastic chip
> never goes below 25 mils, can i change the holes in my board to 25 mils ?
> that shows the standard hole size for everything :-) ?
I use 35 mil for ICs, 1/4w resistors, ceramic caps and similar things.
I use 30 mil holes for TO-92 transistors.
You want the holes somewhat larger than the component leads so you can easily
get the leads in the holes (and out again, when you have to change something!)
I use 25 mil holes only for vias (my board maker charges extra for smaller
holes.)
>
> one last one ...:-) ... If a book were to say that a resistor (in case
> i get some info) has a max hole size of ...say ...20 mils , should
> i make it a bit larger ...like 25 ??
The hole should be 10 - 20 mil larger than the component lead.
Peter Bennett VE7CEI | Vessels shall be deemed to be in sight
Internet: ben...@triumf.ca | of one another only when one can be
Packet: ve7cei@ve7kit.#vanc.bc.ca | observed visually from the other
TRIUMF, Vancouver, B.C., Canada | ColRegs 3(k)
GPS and NMEA info and programs: ftp://sundae.triumf.ca/pub/peter/index.html
Garry Allen
as W. Jones,201H MLH,3193350740,3193382879) writes:
:>
:>From article <17732B717S...@MtSACvm.MtSAC.edu>,
:>by 1RFD...@MtSACvm.MtSAC.edu:
:>
:>> The CAD program i used shows IC , and heck all of the pins for
:>> everything, the same size , 0.035 in or 35 mils.
:>> I checked some databooks and the IC pins for a 16 pin plastic chip
:>> never goes below 25 mils, can i change the holes in my board to 25 mils ?
:>You can, but you won't be able to get the pins in the hole! Give yourself
:>a few mils of clearance to get the pin in the hole and to let the solder
:>wick in between the plated-through hole wall and the pin. With 5 mils of
:>clearance, you'll get the components in in a reasonable amount of time,
:>and with 10 mils of clearance, you'll get the board stuffed quickly. That's
:>why 35 mils is the norm.
:>> What about the size for 1/4 and 1/8 watt resistors, is 25 mils ok ?
:>
:>For most small resistors, you can use the same size you'd use for IC pins.
:>power diodes like the 1N400X family have fat leads, though!
:>> Is there a document that shows the standard hole size for everything?
:>
:>A pair of calipers (vernier or micrometer) will do wonderfully! Even a
:>magnifying loupe and a machinist's scale graduated in 100ths of an inch
:>will do the job.
:> Doug Jones
:> jo...@cs.uiowa.edu
This post should have gone into sci.electronics.cad. But I agree about the
answers given for hole size. To take it one step further, for msot through
hole somponents you should use a hole size of 0.8mm(35 thou). But for some
components you will need to use smaller hole sizes and for some you will need
to use larger hole sizes. Board manufacturers will charge you for the number
of different size drill bits you use. We, believe it or not, have
standardized on the following drill sizes.
0.3mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 1.0mm, 1.3mm, 1.6mm, 2.0mm, 2.4mm, 2.5mm,
3mm, 3.5mm and 4mm.
Ideally you should get hold of mechanical specifications for all the
components you use. These should form the basis for the components you design
onto the board. The CAD package you use should support the use of pins of
different size. Ignoring the small holes, we use the following holes for the
following size leads
lead size hole size
0.3-0.6mm 0.8mm
0.6-0.85mm 1.0mm
0.8-1.1mm 1.3mm
1.1-1.5mm 1.6mm
Often the mechanical specs will also give a recommended layout for the holes
and pads on the PCB. We normally follow these but will modify the hole sizes
as required to fit into our standard hole sizes. It is a major pain to be
forced to a second revision of a board because the component wouldn't fit
into the board.
way...@tensornet.com
> Hi all:
>
> First of all, Thanks to everyone who answer my question on how much
> current a 5 mil trace can stand. You , all, were very helpfull.
>
> Now that i have the prototype ready, i called a PCB manufacturer to
> get a quote and i run into another problem: Hole sizes !!??
>
> The CAD program i used shows IC , and heck all of the pins for
> everything, the same size , 0.035 in or 35 mils.
> I checked some databooks and the IC pins for a 16 pin plastic chip
> never goes below 25 mils, can i change the holes in my board to 25 mils ?
> What about the size for 1/4 and 1/8 watt resistors, is 25 mils ok ?
> I don't have any info on passive components :-( . Is there a document
> that shows the standard hole size for everything :-) ?
>
> one last one ...:-) ... If a book were to say that a resistor (in case
> i get some info) has a max hole size of ...say ...20 mils , should
> i make it a bit larger ...like 25 ??
>
> Please reply to : 1rfd...@ibm.mtsac.edu
>
> Thanks you.
I use these number as a rule-of-thumb when laying out a board.
.028" - via and some TO-92 packages
.035" - most IC packages
.042" - IDC headers, IC's, 1N4000 series diodes, TO-220's, 1/2W Res
.052" - switches, stranded wire, molex headers
.060" - switches, large headers & inter-connects
.086" - mounting holes in TO-220 packages, screw terminals
.125" - mounting holes
.152" - mounting holes
Remember also that if you use plated through holes that the diameter
will be reduced about .003". A little larger hole is easier to deal
with than one too small. Easier to remove a part etc.
Neil Preston <npreston@cctr.umkc.edu>
> From article <17732B717S...@MtSACvm.MtSAC.edu>,
> by 1RFD...@MtSACvm.MtSAC.edu:
>
>> everything, the same size , 0.035 in or 35 mils.
>> I checked some databooks and the IC pins for a 16 pin plastic chip
>> never goes below 25 mils, can i change the holes in my board to 25 mils ?
>
35 mils is common for commercial boards, but if I'm making my own, I use .031
to aid in having enough annular ring. Saves a bit of solder, too, on commer-
cial boards.
>> What about the size for 1/4 and 1/8 watt resistors, is 25 mils ok ?
>
> For most small resistors, you can use the same size you'd use for IC pins.
> power diodes like the 1N400X family have fat leads, though!
>
>> Is there a document that shows the standard hole size for everything?
>
--
Texts: Electronic Drafting and Printed Circuit Board Design, 2nd ed., James M.
Kirkpatrick; Delmar Publishers
The Design and Drafting of printed circuits, Darryl Lindsey; Bishop Graphics,
Inc. Somewhat dated, with focus on taping, but with good valid guidelines.
Kasten, Stephen D. Electronic Prototype Construction; Originally published
by Howard W. Sams, Inc.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Neil Preston, CET Instructor, Electronics Technology
Amateur Radio Station WB0DQW Herndon Technical School
Internet: npre...@cctr.umkc.edu Raytown, Mo.
"Never confuse motion with action." - Benjamin Franklin
Art Zirger
>.028" - via and some TO-92 packages
>.035" - most IC packages
>.042" - IDC headers, IC's, 1N4000 series diodes, TO-220's, 1/2W Res
>.052" - switches, stranded wire, molex headers
>.060" - switches, large headers & inter-connects
>.086" - mounting holes in TO-220 packages, screw terminals
>.125" - mounting holes
>.152" - mounting holes
All parts have a range of hole sizes which will work well for them.
You might very well choose your hole sizes based on what your PCB
vendor charges for tooling costs. Different vendors have different
"complementary" tooling available. The above list looks like the AP
Circuits' PROTO1 drill schedule. Check AP's web site out to get a
better feel for cost tradeoffs (www.apcircuits.com).
Art.
Lewis Hughes
>
> Hi all:
>
> First of all, Thanks to everyone who answer my question on how much
> current a 5 mil trace can stand. You , all, were very helpfull.
>
> Now that i have the prototype ready, i called a PCB manufacturer to
> get a quote and i run into another problem: Hole sizes !!??
>
> everything, the same size , 0.035 in or 35 mils.
> I checked some databooks and the IC pins for a 16 pin plastic chip
> never goes below 25 mils, can i change the holes in my board to 25 mils ?
> that shows the standard hole size for everything :-) ?
>
> one last one ...:-) ... If a book were to say that a resistor (in case
> i get some info) has a max hole size of ...say ...20 mils , should
> i make it a bit larger ...like 25 ??
>
> Please reply to : 1rfd...@ibm.mtsac.edu
>
> Thanks you.
If you want a another answer, MIL-SPEC calls for the hole diameter to be not less
than 0.007 inches and not more than 0.013 inches larger than the component lead
diameter. I have found this to be a very satisfactory guideline. It is not
critical. Just remember that this applies to the finished hole size; so if you
are using plated thru holes, the copper thickness on the walls of the holes is
about 0.001 inches and must be considered in the drill call out.
More holes sizes will cost you more money at the board house. Generally they have
a minimum charge which will be the same for any number of holes of to 6, or 8, or
whatever they have chosen. Different houses, different costing rules.
Remember also, if the component has flat retanglular leads, you must consider the
distance across the diagonal.
Regards,
Lewis
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Having only been laying out PC boards since 1967, maybe someday I will figure out
how to do it! :-)
Sam Goldwasser
FWIW, we use 38 mil holes for prototyping and then go to 35 mil holes
for production (ICs, resistors, small capacitors, etc.). The 38 mil hole
allows for much easier component removal if needed but still has adequate
annular ring for prototype runs.
--- sam
Andrew Benzie
>
> First of all, Thanks to everyone who answer my question on how much
> current a 5 mil trace can stand. You , all, were very helpfull.
>
> Now that i have the prototype ready, i called a PCB manufacturer to
>
The MIL Standard is a good place to start.
Don't forget that manufacturers normally charge you for each drill
size used as well as hole count, so try to keep to a limited
number of sizes. Normally <6, depending on mounting hole requirements!