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From:	"Chad Parker (parker DOT charles AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Date:	Fri, 13 Jul 2018 07:09:36 -0400
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Subject:	Re: [geda-user] Thermals: size problem, SMD
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It can be a problem when installing the parts too, not just removing them.
I've had technicians complain to me about this before... "I had to use TWO
soldering irons just to solder that one pin..."

On Fri, Jul 13, 2018 at 5:52 AM, Richard Rasker (rasker AT linetec DOT nl) [via
geda-user AT delorie DOT com] <geda-user AT delorie DOT com> wrote:

> Hello DJ,
>
> Op 12-07-18 om 22:36 schreef DJ Delorie:
>
>> "Richard Rasker (rasker AT linetec DOT nl) [via geda-user AT delorie DOT com]"
>> <geda-user AT delorie DOT com> writes:
>>
>>> 1: When I create small vias with a thermal, e.g. 0.3 mm drill width,
>>> 0.15 mm annulus width and 0.15 mm clearing, the resulting four thermal
>>> connections to the surrounding copper plane get so narrow (just below
>>> 0.125 mm), that my PCB manufacturer flags a warning.
>>>
>> The Thermal[] entry in your *.pcb sets the thermal ratio; the default is
>> 0.5.
>>
>> http://pcb.geda-project.org/pcb-4.1.2/pcb.html#Thermal-syntax
>>
>
> OK, this goes some way to explain things.
> And I see that the actual thermal finger width is always very slightly
> less than the ration mentioned, so a clearance gap of 0.13 mm (not 0.15 as
> mentioned above) results in a finger width of 0.124 mm. Which is why my PCB
> house complains...
>
> 2: SMD thermals, or the lack thereof. If I really need thermals, I
>>> create tiny rectangles without clearance (S key) to connect pads to the
>>> surrounding copper planes.
>>>
>> Lack thereof.  Technically possible, but difficult to guess what kinds
>> of thermals work for the wide range of SMD pad shapes and groupings.
>>
>
> Yes, I gathered this already from earlier information here.
>
> One important question still is if (and when) those SMD thermals are
> necessary, recommended, or merely a matter of preference.
>
> I see the use in case I want to be able to take certain components off
> with soldering tweezers, but otherwise I never had any structural problems
> with component pads fully connected to the surrounding copper plane.
>
> Best regards,
>
> Richard Rasker
>

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Content-Type: text/html; charset="UTF-8"
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<div dir=3D"ltr">It can be a problem when installing the parts too, not jus=
t removing them. I&#39;ve had technicians complain to me about this before.=
.. &quot;I had to use TWO soldering irons just to solder that one pin...&qu=
ot;<br></div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On F=
ri, Jul 13, 2018 at 5:52 AM, Richard Rasker (<a href=3D"mailto:rasker AT linet=
ec.nl">rasker AT linetec DOT nl</a>) [via <a href=3D"mailto:geda-user AT delorie DOT com"=
>geda-user AT delorie DOT com</a>] <span dir=3D"ltr">&lt;<a href=3D"mailto:geda-us=
er AT delorie DOT com" target=3D"_blank">geda-user AT delorie DOT com</a>&gt;</span> wrot=
e:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-l=
eft:1px #ccc solid;padding-left:1ex">Hello DJ,<br>
<br>
Op 12-07-18 om 22:36 schreef DJ Delorie:<span class=3D""><br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">
&quot;Richard Rasker (<a href=3D"mailto:rasker AT linetec DOT nl" target=3D"_blank=
">rasker AT linetec DOT nl</a>) [via <a href=3D"mailto:geda-user AT delorie DOT com" targ=
et=3D"_blank">geda-user AT delorie DOT com</a>]&quot;<br>
&lt;<a href=3D"mailto:geda-user AT delorie DOT com" target=3D"_blank">geda-user AT de=
lorie.com</a>&gt; writes:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">
1: When I create small vias with a thermal, e.g. 0.3 mm drill width,<br>
0.15 mm annulus width and 0.15 mm clearing, the resulting four thermal<br>
connections to the surrounding copper plane get so narrow (just below<br>
0.125 mm), that my PCB manufacturer flags a warning.<br>
</blockquote>
The Thermal[] entry in your *.pcb sets the thermal ratio; the default is<br=
>
0.5.<br>
<br>
<a href=3D"http://pcb.geda-project.org/pcb-4.1.2/pcb.html#Thermal-syntax" r=
el=3D"noreferrer" target=3D"_blank">http://pcb.geda-project.org/pc<wbr>b-4.=
1.2/pcb.html#Thermal-synta<wbr>x</a><br>
</blockquote>
<br></span>
OK, this goes some way to explain things.<br>
And I see that the actual thermal finger width is always very slightly less=
 than the ration mentioned, so a clearance gap of 0.13 mm (not 0.15 as ment=
ioned above) results in a finger width of 0.124 mm. Which is why my PCB hou=
se complains...<span class=3D""><br>
<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><blockquote class=3D"gmail_quote" style=3D"m=
argin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
2: SMD thermals, or the lack thereof. If I really need thermals, I<br>
create tiny rectangles without clearance (S key) to connect pads to the<br>
surrounding copper planes.<br>
</blockquote>
Lack thereof.=C2=A0 Technically possible, but difficult to guess what kinds=
<br>
of thermals work for the wide range of SMD pad shapes and groupings.<br>
</blockquote>
<br></span>
Yes, I gathered this already from earlier information here.<br>
<br>
One important question still is if (and when) those SMD thermals are necess=
ary, recommended, or merely a matter of preference.<br>
<br>
I see the use in case I want to be able to take certain components off with=
 soldering tweezers, but otherwise I never had any structural problems with=
 component pads fully connected to the surrounding copper plane.<br>
<br>
Best regards,<br>
<br>
Richard Rasker<br>
</blockquote></div><br></div>

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