In design, layout is an important part. The quality of the layout result will directly affect the effect of the wiring, so it can be considered that a reasonable layout is the first step to a successful BPA design. Especially the pre-layout is the process of thinking about the entire circuit board, signal flow, heat dissipation, structure and other structures. If the pre-layout fails, no amount of effort will be needed.

PCB layout design The design process flow of printed circuit boards includes schematic design, electronic component database registration, design preparation, block division, electronic component configuration, configuration confirmation, wiring and final inspection. In the process of the process, no matter which process is found to be a problem, it must be returned to the previous process for reconfirmation or correction.

Artikel ini mula-mula memperkenalkan peraturan dan teknik reka bentuk susun atur PCB, dan kemudian menerangkan cara mereka bentuk dan memeriksa susun atur PCB, daripada keperluan DFM susun atur, keperluan reka bentuk terma, keperluan integriti isyarat, keperluan EMC, tetapan lapisan dan keperluan pembahagian tanah kuasa, dan modul kuasa. Keperluan dan aspek lain akan dianalisis secara terperinci, dan ikuti editor untuk mengetahui butirannya.

Peraturan reka bentuk susun atur PCB

1. Under normal circumstances, all components should be arranged on the same surface of the circuit board. Only when the top-level components are too dense, can some devices with limited height and low heat generation, such as chip resistors, chip capacitors, and chip capacitors, be installed. Chip IC, etc. are placed on the lower layer.

2. Di bawah premis memastikan prestasi elektrik, komponen hendaklah diletakkan pada grid dan disusun selari atau berserenjang antara satu sama lain supaya kemas dan cantik. Dalam keadaan biasa, komponen tidak dibenarkan bertindih; susunan komponen hendaklah padat, dan komponen hendaklah disusun pada keseluruhan susun atur. Pengagihan adalah seragam dan padat.

3. The minimum distance between adjacent land patterns of different components on the circuit board should be above 1mm.

4. The distance from the edge of the circuit board is generally not less than 2MM. The best shape of the circuit board is rectangular, and the aspect ratio is 3:2 or 4:3. When the size of the circuit board is larger than 200MM by 150MM, consider what the circuit board can withstand Mechanical strength.

PCB layout design skills

Dalam reka bentuk susun atur PCB, unit papan litar perlu dianalisis, dan reka bentuk susun atur harus berdasarkan fungsi permulaan. Apabila meletakkan semua komponen litar, prinsip berikut harus dipenuhi:

1. Susun kedudukan setiap unit litar berfungsi mengikut aliran litar, supaya susun atur adalah mudah untuk peredaran isyarat, dan isyarat disimpan dalam arah yang sama sebanyak mungkin [1].

2. Take the core components of each functional unit as the center and lay out around him. The components should be uniformly, integrally and compactly arranged on the PCB to minimize and shorten the leads and connections between the components.

3. For circuits operating at high frequencies, the distribution parameters between components must be considered. In general circuits, components should be arranged in parallel as much as possible, which is not only beautiful, but also easy to install and easy to mass produce.

Cara mereka bentuk dan memeriksa susun atur PCB

1. DFM requirements for layout

1. The optimal process route has been determined, and all devices have been placed on the board.

2. The origin of the coordinates is the intersection of the left and lower extension lines of the board frame, or the lower left pad of the lower left socket.

3. The actual size of the PCB, the location of the positioning device, etc. are consistent with the process structure element map, and the device layout of the area with restricted device height requirements meets the requirements of the structure element map.

4. Kedudukan suis dail, set semula peranti, lampu penunjuk, dsb. adalah sesuai, dan bar pemegang tidak mengganggu peranti sekeliling.

5. Rangka luar papan mempunyai radian licin 197mil, atau direka bentuk mengikut lukisan saiz struktur.

6. Ordinary boards have 200mil process edges; the left and right sides of the backplane have process edges greater than 400mil, and the upper and lower sides have process edges greater than 680mil. The device placement does not conflict with the window opening position.

7. All kinds of additional holes (ICT positioning hole 125mil, handle bar hole, elliptical hole and fiber holder hole) that need to be added are all missing and set correctly.

8. Padang pin peranti, arah peranti, padang peranti, perpustakaan peranti, dsb. yang telah diproses oleh pematerian gelombang mengambil kira keperluan pematerian gelombang.

9. The device layout spacing meets the assembly requirements: surface mount devices are greater than 20mil, IC is greater than 80mil, and BGA is greater than 200mil.

10. Bahagian pengelim mempunyai lebih daripada 120 mil dalam jarak permukaan komponen, dan tiada peranti di kawasan melalui bahagian pengelim pada permukaan kimpalan.

11. Tiada peranti pendek antara peranti tinggi dan tiada peranti tampalan dan peranti selang pendek dan kecil diletakkan dalam jarak 5mm antara peranti dengan ketinggian lebih daripada 10mm.

12. Peranti kutub mempunyai logo skrin sutera kekutuban. Arah X dan Y bagi jenis komponen pemalam terkutub yang sama adalah sama.

13. All devices are clearly marked, no P*, REF, etc. are not clearly marked.

14. There are 3 positioning cursors on the surface containing SMD devices, which are placed in an “L” shape. The distance between the center of the positioning cursor and the edge of the board is greater than 240 mils.

15. Jika anda perlu melakukan pemprosesan boarding, susun atur dianggap memudahkan proses boarding dan PCB dan pemasangan.

16. Tepi yang terkelupas (tepi yang tidak normal) hendaklah diisi dengan menggunakan alur penggilingan dan lubang setem. Lubang setem ialah lompang bukan logam, umumnya diameter 40 mil dan 16 mil dari tepi.

17. The test points used for debugging have been added in the schematic diagram, and they are placed appropriately in the layout.

Second, the thermal design requirements of the layout

1. Heating components and exposed components of the casing are not in close proximity to wires and heat-sensitive components, and other components should also be properly kept away.

2. The placement of the radiator takes into account the convection problem, and there is no interference of high components in the projection area of ​​the radiator, and the range is marked on the mounting surface with silk screen.

3. Susun atur mengambil kira saluran pelesapan haba yang munasabah dan licin.

4. Kapasitor elektrolitik hendaklah diasingkan dengan betul daripada peranti haba tinggi.

5. Pertimbangkan pelesapan haba peranti berkuasa tinggi dan peranti di bawah gusset.

Third, the signal integrity requirements of the layout

1. The start-end matching is close to the sending device, and the end matching is close to the receiving device.

2. Place decoupling capacitors close to related devices

3. Place crystals, crystal oscillators and clock drive chips close to related devices.

4. High-speed and low-speed, digital and analog are arranged separately according to modules.

5. Determine the topological structure of the bus based on the analysis and simulation results or the existing experience to ensure that the system requirements are met.

6. If it is to modify the board design, simulate the signal integrity problem reflected in the test report and give a solution.

7. The layout of the synchronous clock bus system meets the timing requirements.

Empat, keperluan EMC

1. Inductive devices that are prone to magnetic field coupling, such as inductors, relays, and transformers, should not be placed close to each other. When there are multiple inductance coils, the direction is vertical and they are not coupled.

2. Untuk mengelakkan gangguan elektromagnet antara peranti pada permukaan kimpalan papan tunggal dan papan tunggal bersebelahan, tiada peranti sensitif dan peranti sinaran kuat harus diletakkan pada permukaan kimpalan papan tunggal.

3. The interface components are placed close to the edge of the board, and appropriate EMC protection measures have been taken (such as shielding shells, hollowing out of the power supply ground, etc.) to improve the EMC capability of the design.

4. Litar perlindungan diletakkan berhampiran litar antara muka, mengikut prinsip perlindungan pertama dan kemudian penapisan.

5. The distance from the shielding body and the shielding shell to the shielding body and shielding cover shell is more than 500 mils for the devices with high transmitting power or particularly sensitive (such as crystal oscillators, crystals, etc.).

6. A 0.1uF capacitor is placed near the reset line of the reset switch to keep the reset device and reset signal away from other strong devices and signals.

Five, layer setting and power supply and ground division requirements

1. Apabila dua lapisan isyarat bersebelahan terus antara satu sama lain, peraturan pendawaian menegak mesti ditentukan.

2. Lapisan kuasa utama adalah bersebelahan dengan lapisan tanah yang sepadan sebanyak mungkin, dan lapisan kuasa memenuhi peraturan 20H.

3. Each wiring layer has a complete reference plane.

4. Papan berbilang lapisan dilapisi dan bahan teras (TERAS) adalah simetri untuk mengelakkan ledingan yang disebabkan oleh pengagihan ketumpatan kulit kuprum yang tidak sekata dan ketebalan medium yang tidak simetri.

5. Ketebalan papan hendaklah tidak melebihi 4.5mm. Bagi mereka yang mempunyai ketebalan lebih daripada 2.5mm (satah belakang lebih besar daripada 3mm), juruteknik sepatutnya mengesahkan bahawa tiada masalah dengan pemprosesan, pemasangan dan peralatan PCB, dan ketebalan papan kad PC ialah 1.6mm.

6. Apabila nisbah ketebalan-ke-diameter melalui lebih besar daripada 10:1, ia akan disahkan oleh pengeluar PCB.

7. The power and ground of the optical module are separated from other power and ground to reduce interference.

8. Kuasa dan pemprosesan tanah bagi komponen utama memenuhi keperluan.

9. When impedance control is required, the layer setting parameters meet the requirements.

Six, power module requirements

1. The layout of the power supply part ensures that the input and output lines are smooth and do not cross.

2. Apabila papan tunggal membekalkan kuasa kepada subboard, letakkan litar penapis yang sepadan berhampiran alur keluar kuasa papan tunggal dan salur masuk kuasa subboard.

Seven, other requirements

1. The layout takes into account the overall smoothness of the wiring, and the main data flow is reasonable.

2. Laraskan penetapan pin pengecualian, FPGA, EPLD, pemandu bas dan peranti lain mengikut hasil reka letak untuk mengoptimumkan reka letak.

3. Susun atur mengambil kira pertambahan ruang yang sesuai pada pendawaian padat untuk mengelakkan keadaan ia tidak boleh dialihkan.

4. Jika bahan khas, peranti khas (seperti 0.5mmBGA, dll.), dan proses khas diterima pakai, tempoh penghantaran dan kebolehprosesan telah dipertimbangkan sepenuhnya, dan disahkan oleh pengilang PCB dan kakitangan proses.

5. The pin corresponding relationship of the gusset connector has been confirmed to prevent the direction and orientation of the gusset connector from being reversed.

6. If there are ICT test requirements, consider the feasibility of adding ICT test points during layout, so as to avoid difficulty in adding test points during the wiring phase.

7. When a high-speed optical module is included, the layout of the optical port transceiver circuit is prioritized.

8. Selepas susun atur selesai, lukisan pemasangan 1:1 telah disediakan untuk kakitangan projek menyemak sama ada pemilihan pakej peranti adalah betul terhadap entiti peranti.

9. Pada pembukaan tingkap, satah dalam telah dianggap ditarik balik, dan kawasan larangan pendawaian yang sesuai telah ditetapkan.