Circuit design skills PCB proses desain

Proses desain dasar PCB secara umum adalah sebagai berikut: persiapan awal – >; PCB structure design -& GT; Tata letak PCB – & gt; Pengkabelan – & gt; Optimalisasi perutean dan sablon – > Network and DRC inspections and structural inspections – > Plate making.

First: preparation. This includes preparing component libraries and schematics. “To do good work, must first sharpen its device”, to make a good board, in addition to the principle of good design, but also draw well. Before PCB design, the component library of schematic SCH and the component library of PCB should be prepared first. Peotel libraries can be used, but in general it is difficult to find a suitable library, it is best to make your own library according to the standard size information of the selected device. In principle, make PCB component library first, and then SCH component library. Persyaratan perpustakaan komponen PCB tinggi, secara langsung mempengaruhi pemasangan papan; SCH’s component library requirements are relatively loose, as long as attention is paid to the definition of pin attributes and the corresponding relationship with PCB components. PS: Note the hidden pins in the standard library. Kemudian adalah desain skema, siap untuk melakukan desain PCB.

Kedua: desain struktural PCB. Pada langkah ini, sesuai dengan ukuran papan sirkuit dan pemosisian mekanis, permukaan papan PCB digambar dalam lingkungan desain PCB, dan konektor, tombol/sakelar, lubang sekrup, lubang rakitan, dan sebagainya ditempatkan sesuai dengan persyaratan pemosisian. And fully consider and determine the wiring area and non-wiring area (such as how much of the screw hole around the non-wiring area).

Ketiga: tata letak PCB. Layout is basically putting devices on a board. At this point, if all the preparatory work mentioned above is done, the network table can be generated on the schematic diagram (Design- >; CreateNetlist), lalu impor tabel jaringan pada diagram PCB (design-gt; LoadNet). Lihat keriuhan perangkat dari seluruh tumpukan, antara pin dan koneksi cepat garis terbang. Anda kemudian dapat menata perangkat. Tata letak umum dilakukan sesuai dengan prinsip-prinsip berikut:

(1). According to the electrical performance reasonable partition, generally divided into: digital circuit area (that is, afraid of interference, and interference), analog circuit area

(fear of interference), power drive area (interference source);

(2). Complete the same function of the circuit, should be placed as close as possible, and adjust the components to ensure the most simple connection; At the same time, adjust the relative position between the functional blocks to make the connection between the functional blocks the most concise;

(3). Installation position and installation intensity should be considered for components with large mass; Elemen pemanas harus dipisahkan dari elemen sensitif suhu, dan jika perlu, tindakan konveksi termal harus dipertimbangkan;

(4). I/O drive device as close as possible to the edge of the printing plate, close to the outlet connector;

(5). Clock generator (such as: crystal oscillator or clock oscillator) should be as close as possible to the device using the clock;

6. In each integrated circuit between the power input pin and the ground, need to add a decoupling capacitor (generally using high frequency good monolithic capacitor); Kapasitor tantalum juga dapat ditempatkan di sekitar beberapa sirkuit terpadu ketika ruang papan sirkuit sempit.

Semua pemilik tanah. Relay coil to add discharge diode (1N4148 can be);

Today. Layout requirements should be balanced, dense and orderly, not top-heavy or heavy

— Special attention should be paid to the actual size (area and height) of the components and the relative position of the components when placing the components to ensure the electrical performance of the circuit board and the feasibility and convenience of production and installation. At the same time, the above principles should be reflected

Under the premise, modify the placement of devices appropriately to make them neat and beautiful. For example, the same devices should be placed neatly and in the same direction, instead of being “strewn at random”. This step concerns the difficulty of board integral figure and next wiring degree, want to spend big effort to consider so. When layout, can make preliminary wiring first to not quite affirmative place, sufficient consideration.

Keempat: kabel. Pengkabelan adalah proses terpenting dalam desain PCB. Ini secara langsung akan mempengaruhi kinerja papan PCB. In the process of PCB design, wiring generally has such three levels of division: the first is the distribution, which is the most basic requirement of PCB design. If the line is not cloth, get everywhere is flying line, it will be a unqualified board, can say that there is no entry. The second is the satisfaction of electrical performance. Ini adalah standar untuk mengukur apakah papan sirkuit tercetak memenuhi syarat. This is after the distribution, carefully adjust the wiring, so that it can achieve the best electrical performance. Kemudian ada estetika. Jika kain pengkabelan Anda terhubung, juga tidak memiliki tempat yang mempengaruhi kinerja alat listrik, tetapi melihat masa lalu dengan acuh tak acuh, tambahkan warna-warni, berwarna cerah, yang menghitung seberapa baik kinerja alat listrik Anda, masih menjadi sampah di mata orang lain. This brings great inconvenience to testing and maintenance. Pengkabelan harus rapi dan seragam, tidak saling silang tanpa aturan. Semua ini harus dicapai dalam konteks memastikan kinerja listrik dan memenuhi persyaratan individu lainnya, jika tidak maka akan meninggalkan esensi. Pengkabelan harus dilakukan sesuai dengan prinsip-prinsip berikut:

(1). Secara umum, kabel daya dan kabel ground harus dirutekan terlebih dahulu untuk memastikan kinerja listrik papan sirkuit. Dalam ruang lingkup yang memungkinkan, perlebar lebar catu daya, kabel arde sejauh mungkin, sebaiknya kabel arde lebih lebar dari saluran listrik, hubungannya adalah: kabel arde > saluran listrik > saluran sinyal, biasanya lebar saluran sinyal adalah : 0.2 ~ 0.3mm, lebar tertipis bisa mencapai 0.05 ~ 0.07mm, saluran listrik adalah 1.2 ~ 2.5mm umumnya. PCB sirkuit digital dapat digunakan di sirkuit dengan konduktor ground lebar, yaitu jaringan ground. (Pembumian analog tidak dapat digunakan dengan cara ini.)

(2). In advance, wire strict requirements (such as high frequency line) for wiring, input and output side line should avoid adjacent parallel, so as not to produce reflection interference. When necessary, ground wire should be added to isolate, and the wiring of two adjacent layers should be perpendicular to each other, which is easy to produce parasitic coupling in parallel.

(3). The oscillator housing should be grounded, and the clock line should be as short as possible, and not spread all over the place. Below the clock oscillation circuit, the special high-speed logic circuit should increase the area of the ground, and should not go to other signal lines, so that the surrounding electric field tends to zero;

(4). In order to reduce the radiation of high frequency signal, 45O broken line should be used as far as possible, instead of 90O broken line. (High requirements of the line also use double arc)

(5). Any signal line should not form a loop, if unavoidable, loop should be as small as possible; Garis sinyal melalui lubang harus sesedikit mungkin;

6. Garis kunci harus pendek dan tebal, dengan perlindungan di kedua sisi.

Semua pemilik tanah. When the sensitive signal and noise field signal are transmitted through flat cable, the method of “ground – signal – ground wire” is used.

Today. Test points should be reserved for key signals to facilitate production and maintenance testing

Pet-name ruby. After schematic diagram wiring is completed, wiring should be optimized; At the same time, after the preliminary network check and DRC check is correct, the ground wire is filled in the area without wiring, and a large area of copper layer is used as ground wire, and the unused places are connected with the ground as ground wire on the printed board. Atau buat papan multi-layer, catu daya, saluran grounding masing-masing menempati lapisan.

— PCB wiring process requirements

(1). line

Generally, the signal line width is 0.3mm(12mil), and the power line width is 0.77mm(30mil) or 1.27mm(50mil). Line with

The distance between lines and between lines and pads should be greater than or equal to 0.33mm(13mil). In practical application, it should be considered to increase the distance when conditions permit; When the cabling density is high, it is advisable (but not recommended) to use two cables between IC pins. The width of the cables is 0.254mm(10mil), and the distance between the cables is not less than 0.254mm(10mil).

Under special circumstances, when the pin of the device is dense and the width is narrow, the line width and line spacing can be appropriately reduced.

(2). PAD (PAD)

The basic requirements of PAD and transition hole (VIA) are: the diameter of PAD is greater than 0.6mm than the diameter of hole; For example, universal pin type resistors, capacitors and integrated circuits, using disk/hole size 1.6mm/0.8mm (63mil/32mil), socket, pin and diode 1N4007, using 1.8mm/1.0mm (71mil/39mil). In practical application, it should be determined according to the size of the actual components. If conditions are available, the size of the pad can be appropriately increased. The installation aperture of the components designed on the PCB board should be about 0.2 ~ 0.4mm larger than the actual size of the pins.

(3). Through hole (VIA)

Generally 1.27mm/0.7mm(50mil/28mil);

When the wiring density is high, the hole size can be appropriately reduced, but not too small, can consider 1.0mm/0.6mm(40mil/24mil).

(4). Spacing requirements for pads, wires and through-holes

PADandVIA: ≥0.3mm (12mil)

PADandPAD: 0.3mm (12mil)

PADandTRACK: ≥0.3mm (12mil)

TRACKandTRACK: ≥0.3mm (12mil)

Ketika kepadatan tinggi:

PADandVIA: ≥0.254mm (10mil)

PADandPAD: 0.254mm (10mil)

PADandTRACK: ≥0.254mm (10mil)

TRACKandTRACK: ≥0.254mm (10mil)

Kelima: pengoptimalan kabel dan sablon. “Tidak ada yang terbaik, hanya lebih baik”! Tidak peduli berapa banyak usaha yang Anda lakukan untuk desain, ketika Anda selesai, lihat lagi, dan Anda masih akan merasa bahwa Anda dapat banyak berubah. Aturan desain umum adalah bahwa pengkabelan yang optimal membutuhkan waktu dua kali lebih lama dari pengkabelan awal. Setelah Anda merasa tidak ada yang perlu diperbaiki, Anda dapat menempatkan tembaga. PoligonPlane). Peletakan tembaga umumnya meletakkan kabel tanah (perhatikan pemisahan tanah analog dan digital), papan multilayer mungkin juga perlu meletakkan daya. Untuk sablon, kita harus memperhatikan agar tidak terhalang oleh perangkat atau terlepas oleh lubang dan bantalan. Pada saat yang sama, desain untuk menghadapi permukaan komponen, bagian bawah kata harus menjadi pemrosesan cermin, agar tidak membingungkan level.

Keenam: pemeriksaan jaringan dan DRC dan pemeriksaan struktur. Pertama, pada premis bahwa desain skematis benar, file jaringan PCB yang dihasilkan dan file jaringan skematik adalah NETCHECK untuk hubungan koneksi fisik, dan desain diubah tepat waktu sesuai dengan hasil file output untuk memastikan kebenaran hubungan koneksi kabel; Setelah pemeriksaan jaringan lulus dengan benar, pemeriksaan DRC akan dilakukan pada desain PCB, dan desain akan diubah sesuai dengan hasil file output pada waktunya untuk memastikan kinerja listrik kabel PCB. Akhirnya, struktur pemasangan mekanis PCB harus diperiksa dan dikonfirmasi lebih lanjut.

Ketujuh: pembuatan piring. It is best to have a review process before doing so.

Desain PCB adalah ujian pikiran pekerjaan, siapa yang dekat dengan pikiran, pengalaman tinggi, desain papannya bagus. Jadi desain harus sangat hati-hati, sepenuhnya mempertimbangkan faktor-faktor dari semua aspek (seperti memudahkan pemeliharaan dan pemeriksaan ini banyak orang tidak mempertimbangkan), keunggulan, akan mampu merancang papan yang baik.