Circuit design skills PCB design process

General PCB basic design process is as follows: preliminary preparation – >; PCB structure design -& GT; PCB sxemasi – & gt; Ulanish – & gt; Yo’nalishni optimallashtirish va ekranni bosib chiqarish -> 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. Asosan, avval PCB komponentlar kutubxonasini, so’ngra SCH komponentlar kutubxonasini yarating. PCB komponentlari kutubxonasi talablari yuqori, bu taxtani o’rnatishga bevosita ta’sir qiladi; 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. Keyin sxematik dizayn, PCB dizaynini bajarishga tayyor.

Ikkinchidan: tenglikni strukturaviy dizayni. Ushbu bosqichda, elektron kartaning o’lchami va mexanik joylashuviga ko’ra, tenglikni konstruktsiyasi muhitida tenglikni kartochkasi yuzasi chiziladi va joylashish talablariga muvofiq ulagichlar, tugmalar/kalitlar, vintli teshiklar, yig’ish teshiklari va boshqalar joylashtiriladi. 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).

Uchinchidan: PCB tartibi. 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), so’ngra PCB diagrammasidagi tarmoq jadvalini import qiling (design-gt; LoadNets). Qoziq va uchish liniyasi o’rtasida tezlik bilan ulanadigan butun qoziqning qurilma uyasini ko’ring. Shundan so’ng siz qurilmani yotqizishingiz mumkin. Umumiy tartib quyidagi printsiplarga muvofiq amalga oshiriladi:

(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; Isitish elementini harorat sezgir elementdan ajratish kerak va agar kerak bo’lsa, termal konveksiya choralarini ko’rib chiqish kerak;

(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); Tantal kondansatörü, shuningdek, elektron karta bo’sh joy tor bo’lganda, bir nechta integral mikrosxemalar atrofida joylashtirilishi mumkin.

Hamma er egalari. Relay coil to add discharge diode (1N4148 can be);

Bugun. 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.

To’rtinchidan: simlarni ulash. PCB dizaynidagi simlarni ulash eng muhim jarayondir. Bu to’g’ridan -to’g’ri PCB kartasining ishlashiga ta’sir qiladi. PCBni loyihalash jarayonida simlar odatda uchta bo’linish darajasiga ega: birinchisi – bu PCB dizaynining eng asosiy talabi. 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. Bu bosilgan elektron kartaning malakali ekanligini o’lchash uchun standart. This is after the distribution, carefully adjust the wiring, so that it can achieve the best electrical performance. Keyin estetika paydo bo’ladi. Agar sizning elektr simingiz ulangan bo’lsa, unda elektr jihozlarining ishlashiga ta’sir qiladigan joy yo’q, lekin o’tmishga befarq qarang, rang -barang, yorqin rang qo’shing, bu sizning elektr jihozingizning ishlashini hisoblab chiqadi, lekin boshqalarning ko’ziga axlat bo’lib qolaveradi. This brings great inconvenience to testing and maintenance. Elektr o’tkazgichlari tartibsiz va bir xil bo’lishi kerak, qoidalarsiz. Bularning barchasiga elektr ishlashini ta’minlash va boshqa individual talablarga javob berish sharoitida erishish kerak, aks holda bu mohiyatdan voz kechishdir. Kabelni ulash quyidagi printsiplarga muvofiq amalga oshirilishi kerak:

(1). Umuman olganda, elektron kartaning elektr ishlashini ta’minlash uchun birinchi navbatda elektr kabeli va er kabeli o’tkazilishi kerak. Iloji boricha elektr tarmog’ining kengligini kengaytirish sharti bilan, er simlari elektr uzatish liniyasidan kengroq bo’lishi yaxshiroqdir, ularning aloqasi: er simlari> elektr uzatish liniyasi> signal chizig’i, odatda signal chizig’ining kengligi : 0.2 ~ 0.3 mm, eng nozik kengligi 0.05 ~ 0.07 mm ga etishi mumkin, elektr tarmog’i odatda 1.2 ~ 2.5 mm. The PCB of a digital circuit can be used in a circuit with wide ground conductors, that is, a ground network. (Analog ground cannot be used in this way.)

(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; Teshik orqali signal chizig’i iloji boricha kamroq bo’lishi kerak;

6. Kalit chiziq qisqa va qalin bo’lishi kerak, har ikki tomondan himoyalangan.

Hamma er egalari. When the sensitive signal and noise field signal are transmitted through flat cable, the method of “ground – signal – ground wire” is used.

Bugun. 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. Or make it multi-layer board, power supply, grounding line each occupy a layer.

— PCB wiring process requirements

(1). chiziq

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: ≥0.3 mm (12 mil)

PADandTRACK: ≥0.3mm (12mil)

TRACKandTRACK: ≥0.3mm (12mil)

Qachon zichlik yuqori bo’lsa:

PADandVIA: ≥0.254mm (10mil)

PADandPAD: ≥0.254 mm (10 mil)

PADandTRACK: ≥0.254mm (10mil)

TRACKandTRACK: ≥0.254mm (10mil)

Beshinchisi: simlarni optimallashtirish va ekranni bosib chiqarish. “Eng yaxshisi yo’q, faqat yaxshiroq”! Dizaynga qancha kuch sarflamasligingizdan qat’i nazar, ishni tugatganingizdan so’ng, unga yana bir qarang, shunda ham siz ko’p narsani o’zgartira olasiz. Umumiy konstruktiv qoida shundaki, eng maqbul simlarni ulash dastlabki simlardan ikki barobar ko’proq vaqtni oladi. Hech narsa tuzatishga hojat yo’qligini sezganingizda, misni qo’yishingiz mumkin. Ko’pburchak tekislik). Misni yotqizish odatda er simini yotqizadi (analog va raqamli topraklamani ajratishga e’tibor bering), ko’p qatlamli taxtaga ham quvvat sarflanishi kerak bo’lishi mumkin. Ekranni bosib chiqarish uchun biz qurilma blokirovka qilinmasligiga yoki teshik va yostiq tomonidan olib tashlanmasligiga e’tibor qaratishimiz kerak. Shu bilan birga, dizayn komponentlar yuzasiga qarab turishi uchun, so’zning pastki qismi oynani qayta ishlash bo’lishi kerak.

Oltinchisi: tarmoq va DRCni tekshirish va tuzilmani tekshirish. Birinchidan, sxematik dizayn to’g’ri ekanligiga asoslanib, hosil qilingan PCB tarmoq fayllari va sxematik tarmoq fayllari jismoniy ulanish munosabatlari uchun NETCHECK hisoblanadi va kabelning ulanish munosabatlarining to’g’riligini ta’minlash uchun dizayndagi chiqish fayli natijalariga ko’ra o’z vaqtida tuzatishlar kiritiladi; Tarmoq tekshiruvi to’g’ri o’tkazilgandan so’ng, PCB konstruktsiyasida DRC tekshiruvi o’tkaziladi va PCB simlarining elektr ishlashini ta’minlash uchun dizayndagi chiqish fayli natijalariga ko’ra o’z vaqtida tuzatishlar kiritiladi. Nihoyat, PCBning mexanik o’rnatish tuzilishi qo’shimcha tekshirilishi va tasdiqlanishi kerak.

Ettinchi: plastinka yasash. It is best to have a review process before doing so.

PCB dizayni – bu ish ongining sinovi, u aqlga yaqin, yuqori tajribaga ega, taxtaning dizayni yaxshi. Shunday qilib, dizayn juda ehtiyotkorlik bilan bo’lishi kerak, barcha jihatlarning omillarini to’liq hisobga olishi kerak (masalan, texnik xizmat ko’rsatishni osonlashtirish va ko’p odamlar buni o’ylamaydi), mukammallik, yaxshi taxtani loyihalash imkoniyatiga ega bo’ladi.