Why are there so many vias on this board?

The name of the pictureThe name of the pictureThe name of the pictureClash Royale CLAN TAG#URR8PPP











up vote
2
down vote

favorite












I was looking at the MMZ09312BT1 development board layout and I'm curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as a filter?) ?



Also it doesn't say explicitly, but is it possible to tell if they have a ground plane on the bottom layer ?



Datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf



Development board on page 8



enter image description here










share|improve this question

























    up vote
    2
    down vote

    favorite












    I was looking at the MMZ09312BT1 development board layout and I'm curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as a filter?) ?



    Also it doesn't say explicitly, but is it possible to tell if they have a ground plane on the bottom layer ?



    Datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf



    Development board on page 8



    enter image description here










    share|improve this question























      up vote
      2
      down vote

      favorite









      up vote
      2
      down vote

      favorite











      I was looking at the MMZ09312BT1 development board layout and I'm curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as a filter?) ?



      Also it doesn't say explicitly, but is it possible to tell if they have a ground plane on the bottom layer ?



      Datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf



      Development board on page 8



      enter image description here










      share|improve this question













      I was looking at the MMZ09312BT1 development board layout and I'm curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as a filter?) ?



      Also it doesn't say explicitly, but is it possible to tell if they have a ground plane on the bottom layer ?



      Datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf



      Development board on page 8



      enter image description here







      rf pcb-design filter






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 1 hour ago









      VanGo

      187112




      187112




















          3 Answers
          3






          active

          oldest

          votes

















          up vote
          2
          down vote













          It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.






          share|improve this answer



























            up vote
            2
            down vote













            This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



            You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.






            share|improve this answer



























              up vote
              1
              down vote













              I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



              What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



              Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



              In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.






              share|improve this answer




















                Your Answer





                StackExchange.ifUsing("editor", function ()
                return StackExchange.using("mathjaxEditing", function ()
                StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix)
                StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["\$", "\$"]]);
                );
                );
                , "mathjax-editing");

                StackExchange.ifUsing("editor", function ()
                return StackExchange.using("schematics", function ()
                StackExchange.schematics.init();
                );
                , "cicuitlab");

                StackExchange.ready(function()
                var channelOptions =
                tags: "".split(" "),
                id: "135"
                ;
                initTagRenderer("".split(" "), "".split(" "), channelOptions);

                StackExchange.using("externalEditor", function()
                // Have to fire editor after snippets, if snippets enabled
                if (StackExchange.settings.snippets.snippetsEnabled)
                StackExchange.using("snippets", function()
                createEditor();
                );

                else
                createEditor();

                );

                function createEditor()
                StackExchange.prepareEditor(
                heartbeatType: 'answer',
                convertImagesToLinks: false,
                noModals: true,
                showLowRepImageUploadWarning: true,
                reputationToPostImages: null,
                bindNavPrevention: true,
                postfix: "",
                imageUploader:
                brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
                contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
                allowUrls: true
                ,
                onDemand: true,
                discardSelector: ".discard-answer"
                ,immediatelyShowMarkdownHelp:true
                );



                );













                 

                draft saved


                draft discarded


















                StackExchange.ready(
                function ()
                StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2felectronics.stackexchange.com%2fquestions%2f405044%2fwhy-are-there-so-many-vias-on-this-board%23new-answer', 'question_page');

                );

                Post as a guest






























                3 Answers
                3






                active

                oldest

                votes








                3 Answers
                3






                active

                oldest

                votes









                active

                oldest

                votes






                active

                oldest

                votes








                up vote
                2
                down vote













                It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.






                share|improve this answer
























                  up vote
                  2
                  down vote













                  It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.






                  share|improve this answer






















                    up vote
                    2
                    down vote










                    up vote
                    2
                    down vote









                    It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.






                    share|improve this answer












                    It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.







                    share|improve this answer












                    share|improve this answer



                    share|improve this answer










                    answered 48 mins ago









                    TimWescott

                    1,22127




                    1,22127






















                        up vote
                        2
                        down vote













                        This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



                        You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.






                        share|improve this answer
























                          up vote
                          2
                          down vote













                          This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



                          You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.






                          share|improve this answer






















                            up vote
                            2
                            down vote










                            up vote
                            2
                            down vote









                            This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



                            You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.






                            share|improve this answer












                            This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



                            You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.







                            share|improve this answer












                            share|improve this answer



                            share|improve this answer










                            answered 20 mins ago









                            ajb

                            2,045516




                            2,045516




















                                up vote
                                1
                                down vote













                                I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



                                What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



                                Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



                                In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.






                                share|improve this answer
























                                  up vote
                                  1
                                  down vote













                                  I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



                                  What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



                                  Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



                                  In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.






                                  share|improve this answer






















                                    up vote
                                    1
                                    down vote










                                    up vote
                                    1
                                    down vote









                                    I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



                                    What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



                                    Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



                                    In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.






                                    share|improve this answer












                                    I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



                                    What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



                                    Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



                                    In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.







                                    share|improve this answer












                                    share|improve this answer



                                    share|improve this answer










                                    answered 23 mins ago









                                    Edgar Brown

                                    34211




                                    34211



























                                         

                                        draft saved


                                        draft discarded















































                                         


                                        draft saved


                                        draft discarded














                                        StackExchange.ready(
                                        function ()
                                        StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2felectronics.stackexchange.com%2fquestions%2f405044%2fwhy-are-there-so-many-vias-on-this-board%23new-answer', 'question_page');

                                        );

                                        Post as a guest













































































                                        Popular posts from this blog

                                        How to check contact read email or not when send email to Individual?

                                        Displaying single band from multi-band raster using QGIS

                                        How many registers does an x86_64 CPU actually have?