• TDR solder mask

    From John Larkin@21:1/5 to All on Tue Jan 25 14:08:59 2022
    https://www.dropbox.com/s/idwz568o8hfpgzb/TDR_Solder_Mask.jpg?raw=1

    The two un-masked patches are not visible on 30 ps TDR. Board
    variations are a lot bigger.

    --

    If a man will begin with certainties, he shall end with doubts,
    but if he will be content to begin with doubts he shall end in certainties. Francis Bacon

    --- SoupGate-Win32 v1.05
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  • From whit3rd@21:1/5 to John Larkin on Tue Jan 25 14:45:57 2022
    On Tuesday, January 25, 2022 at 2:09:11 PM UTC-8, John Larkin wrote:
    https://www.dropbox.com/s/idwz568o8hfpgzb/TDR_Solder_Mask.jpg?raw=1

    The two un-masked patches are not visible on 30 ps TDR. Board
    variations are a lot bigger.


    Makes sense; the mass of the lacquer layer can't be much, and multilayer boards, with glue
    layers, might have more material nonuniformity over modest length scales. Fiberglass
    cloth, too, can be expected to contain some weave variance.

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  • From Gerhard Hoffmann@21:1/5 to All on Tue Jan 25 23:40:32 2022
    Am 25.01.22 um 23:08 schrieb John Larkin:
    https://www.dropbox.com/s/idwz568o8hfpgzb/TDR_Solder_Mask.jpg?raw=1

    The two un-masked patches are not visible on 30 ps TDR. Board
    variations are a lot bigger.

    I got similar results on a JLCPCB 4 layer board.
    I calculated that 50 Ohms are 11.55 mil, drew it 12 mil in
    Altium. Seems to fit.

    < https://www.flickr.com/photos/137684711@N07/51843174578/in/dateposted-public/lightbox/
    >

    The SMA launcher decal was not so good, but I was interested in the 50
    Ohm line only for verifying eps-r and thickness etc.
    The launchers were for a 2 layer process. The streamlined boards
    for the LMX2594 are on the plane from HK. They also have cutouts
    on Layer 2 and shorter SMA center pads. The unpopulated SMA is
    better than the populated one. The thickness of the center pin
    and the solder seem to matter.

    cheers, Gerhard

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to All on Tue Jan 25 19:39:30 2022
    On Tue, 25 Jan 2022 23:40:32 +0100, Gerhard Hoffmann <dk4xp@arcor.de>
    wrote:

    Am 25.01.22 um 23:08 schrieb John Larkin:
    https://www.dropbox.com/s/idwz568o8hfpgzb/TDR_Solder_Mask.jpg?raw=1

    The two un-masked patches are not visible on 30 ps TDR. Board
    variations are a lot bigger.

    I got similar results on a JLCPCB 4 layer board.
    I calculated that 50 Ohms are 11.55 mil, drew it 12 mil in
    Altium. Seems to fit.

    < >https://www.flickr.com/photos/137684711@N07/51843174578/in/dateposted-public/lightbox/
    >

    The SMA launcher decal was not so good, but I was interested in the 50
    Ohm line only for verifying eps-r and thickness etc.
    The launchers were for a 2 layer process. The streamlined boards
    for the LMX2594 are on the plane from HK. They also have cutouts
    on Layer 2 and shorter SMA center pads. The unpopulated SMA is
    better than the populated one. The thickness of the center pin
    and the solder seem to matter.

    cheers, Gerhard

    The quickie Chinese board houses default to super thin layer 1/2
    dielectrics for some reason. If you use layer 2 as ground, that makes
    your SMA pads capacitive anomalies. Even the cutout doesn't seem to be
    enough; fringing maybe.

    Your trace hit 50r pretty good.

    We have one 50-ohm SMA footprint that cuts away all the inner planes
    and plops a big copper square on the farside.

    https://www.dropbox.com/s/hebu7yfzj9mf3lm/Rob1.jpg?raw=1

    That connector has a giant center pin. The center pin in free space,
    not on a board, is 100 ohms!

    https://www.dropbox.com/s/a2weq43lmo1hdch/DSC01527.JPG?raw=1



    --

    I yam what I yam - Popeye

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Gerhard Hoffmann@21:1/5 to All on Wed Jan 26 10:28:15 2022
    Am 26.01.22 um 04:39 schrieb jlarkin@highlandsniptechnology.com:
    On Tue, 25 Jan 2022 23:40:32 +0100, Gerhard Hoffmann <dk4xp@arcor.de>
    wrote:

    Am 25.01.22 um 23:08 schrieb John Larkin:
    https://www.dropbox.com/s/idwz568o8hfpgzb/TDR_Solder_Mask.jpg?raw=1

    The two un-masked patches are not visible on 30 ps TDR. Board
    variations are a lot bigger.

    I got similar results on a JLCPCB 4 layer board.
    I calculated that 50 Ohms are 11.55 mil, drew it 12 mil in
    Altium. Seems to fit.

    <
    https://www.flickr.com/photos/137684711@N07/51843174578/in/dateposted-public/lightbox/
    >

    The SMA launcher decal was not so good, but I was interested in the 50
    Ohm line only for verifying eps-r and thickness etc.
    The launchers were for a 2 layer process. The streamlined boards
    for the LMX2594 are on the plane from HK. They also have cutouts
    on Layer 2 and shorter SMA center pads. The unpopulated SMA is
    better than the populated one. The thickness of the center pin
    and the solder seem to matter.

    cheers, Gerhard

    The quickie Chinese board houses default to super thin layer 1/2
    dielectrics for some reason. If you use layer 2 as ground, that makes
    your SMA pads capacitive anomalies. Even the cutout doesn't seem to be enough; fringing maybe.



    That is needed to get some signal out from under a BGA.
    They also have a process for thicker lines. I think I will
    test it with a UHF LDMOS power amplifier.

    <
    https://www.flickr.com/photos/137684711@N07/51844498620/in/dateposted-public/


    one of the next tries. Red is top = 1, blue = 2,
    yellow = 3 (not in this area) 4 = bottom = green.



    Your trace hit 50r pretty good.

    We have one 50-ohm SMA footprint that cuts away all the inner planes
    and plops a big copper square on the farside.

    https://www.dropbox.com/s/hebu7yfzj9mf3lm/Rob1.jpg?raw=1

    That connector has a giant center pin. The center pin in free space,
    not on a board, is 100 ohms!

    https://www.dropbox.com/s/a2weq43lmo1hdch/DSC01527.JPG?raw=1

    Looks like the center pin on my board. I also have recovered
    some SMAs from junked wafertesters; they have REALLY small
    center pins and a ground tunnel / bridge with 2 hex nuts.
    They might fit the 12 mil line directly. Probably a solder
    problem even with the finest METCAL tip.

    Probably Rosenberger.

    The plane with the new boards has landed in .de in the night. :-)

    Cheers, Gerhard

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to All on Wed Jan 26 07:28:21 2022
    On Wed, 26 Jan 2022 10:28:15 +0100, Gerhard Hoffmann <dk4xp@arcor.de>
    wrote:

    Am 26.01.22 um 04:39 schrieb jlarkin@highlandsniptechnology.com:
    On Tue, 25 Jan 2022 23:40:32 +0100, Gerhard Hoffmann <dk4xp@arcor.de>
    wrote:

    Am 25.01.22 um 23:08 schrieb John Larkin:
    https://www.dropbox.com/s/idwz568o8hfpgzb/TDR_Solder_Mask.jpg?raw=1

    The two un-masked patches are not visible on 30 ps TDR. Board
    variations are a lot bigger.

    I got similar results on a JLCPCB 4 layer board.
    I calculated that 50 Ohms are 11.55 mil, drew it 12 mil in
    Altium. Seems to fit.

    <
    https://www.flickr.com/photos/137684711@N07/51843174578/in/dateposted-public/lightbox/
    >

    The SMA launcher decal was not so good, but I was interested in the 50
    Ohm line only for verifying eps-r and thickness etc.
    The launchers were for a 2 layer process. The streamlined boards
    for the LMX2594 are on the plane from HK. They also have cutouts
    on Layer 2 and shorter SMA center pads. The unpopulated SMA is
    better than the populated one. The thickness of the center pin
    and the solder seem to matter.

    cheers, Gerhard

    The quickie Chinese board houses default to super thin layer 1/2
    dielectrics for some reason. If you use layer 2 as ground, that makes
    your SMA pads capacitive anomalies. Even the cutout doesn't seem to be
    enough; fringing maybe.



    That is needed to get some signal out from under a BGA.
    They also have a process for thicker lines. I think I will
    test it with a UHF LDMOS power amplifier.

    < >https://www.flickr.com/photos/137684711@N07/51844498620/in/dateposted-public/


    one of the next tries. Red is top = 1, blue = 2,
    yellow = 3 (not in this area) 4 = bottom = green.



    Your trace hit 50r pretty good.

    We have one 50-ohm SMA footprint that cuts away all the inner planes
    and plops a big copper square on the farside.

    https://www.dropbox.com/s/hebu7yfzj9mf3lm/Rob1.jpg?raw=1

    That connector has a giant center pin. The center pin in free space,
    not on a board, is 100 ohms!

    https://www.dropbox.com/s/a2weq43lmo1hdch/DSC01527.JPG?raw=1

    Looks like the center pin on my board. I also have recovered
    some SMAs from junked wafertesters; they have REALLY small
    center pins and a ground tunnel / bridge with 2 hex nuts.
    They might fit the 12 mil line directly. Probably a solder
    problem even with the finest METCAL tip.

    Probably Rosenberger.


    Some of the high-end connectors don't need solder. Substitute money.

    The plane with the new boards has landed in .de in the night. :-)

    New boards are always fun.


    Cheers, Gerhard

    This is a nice part:

    MUELLER BU-1420701851
    DIGIKEY 314-1703-ND

    We're paying less than $4.

    A 35 mil wide trace matches the pin width, and you can bury one end of
    an 0603 part in that trace without adding any pad capacitance.

    There's room for a couple of small parts or some silk text inside the footprint, which can be handy.



    --

    I yam what I yam - Popeye

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)