Circuit design skills PCB design process

General PCB basic design process is as follows: preliminary preparation – >; PCB structure design -& GT; Mpangilio wa PCB – & gt; Wiring – & gt; Uboreshaji wa njia na uchapishaji wa skrini -> 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. Kimsingi, fanya maktaba ya sehemu ya PCB kwanza, halafu maktaba ya sehemu ya SCH. Mahitaji ya maktaba ya sehemu ya PCB ni ya juu, inaathiri moja kwa moja ufungaji wa bodi; Mahitaji ya maktaba ya sehemu ya SCH ni huru, maadamu umakini hulipwa kwa ufafanuzi wa sifa za pini na uhusiano unaofanana na vifaa vya PCB. PS: Note the hidden pins in the standard library. Halafu muundo wa skimu, uko tayari kufanya muundo wa PCB.

Pili: muundo wa muundo wa PCB. Katika hatua hii, kulingana na saizi ya bodi ya mzunguko na nafasi ya mitambo, uso wa bodi ya PCB imechorwa katika mazingira ya muundo wa PCB, na viunganishi, vifungo / swichi, mashimo ya screw, mashimo ya mkutano na kadhalika huwekwa kulingana na mahitaji ya nafasi. 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).

Tatu: Mpangilio wa 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), na kisha ingiza meza ya mtandao kwenye mchoro wa PCB (design-gt; Miti ya Mzigo). Tazama kitovu cha kifaa cha rundo zima, kati ya pini na uunganisho wa haraka wa laini ya kuruka. Basi unaweza kuweka kifaa. Mpangilio wa jumla unafanywa kulingana na kanuni zifuatazo:

(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; Kipengele cha kupokanzwa kinapaswa kutengwa na kipengee nyeti cha joto, na ikiwa ni lazima, hatua za ushawishi wa joto zinapaswa kuzingatiwa;

(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); Tantalum capacitor pia inaweza kuwekwa karibu na nyaya kadhaa zilizounganishwa wakati nafasi ya bodi ya mzunguko ni ngumu.

Wamiliki wote wa ardhi. Relay coil to add discharge diode (1N4148 can be);

Leo. 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.

Nne: wiring. Wiring ni mchakato muhimu zaidi katika muundo wa PCB. Hii itaathiri moja kwa moja utendaji wa bodi ya PCB. Katika mchakato wa muundo wa PCB, wiring kwa ujumla ina viwango vitatu vya mgawanyiko: kwanza ni usambazaji, ambayo ndio mahitaji ya msingi ya muundo wa PCB. 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. Hii ndio kiwango cha kupima ikiwa bodi ya mzunguko iliyochapishwa inastahili. This is after the distribution, carefully adjust the wiring, so that it can achieve the best electrical performance. Halafu kuna aesthetics. Ikiwa kitambaa chako cha wiring kiliunganishwa, pia usiwe na mahali pa kuathiri utendaji wa vifaa vya umeme, lakini angalia kwa kutamani, ongeza rangi, rangi nyekundu, ambayo inahesabu jinsi utendaji wako wa vifaa vya umeme ni mzuri, bado uwe takataka kwa macho ya wengine. This brings great inconvenience to testing and maintenance. Wiring inapaswa kuwa nadhifu na sare, sio msalaba bila sheria. Yote hii inapaswa kupatikana katika muktadha wa kuhakikisha utendaji wa umeme na kukidhi mahitaji mengine ya kibinafsi, vinginevyo ni kuachana na kiini. Wiring inapaswa kufanywa kulingana na kanuni zifuatazo:

(1). Kwa ujumla, kebo ya umeme na kebo ya ardhini inapaswa kusafirishwa kwanza ili kuhakikisha utendaji wa umeme wa bodi ya mzunguko. Katika upeo ambao hali inaruhusu, panua upana wa usambazaji wa umeme, waya wa ardhi kadri inavyowezekana, ni bora waya ya ardhi iwe pana kuliko laini ya nguvu, uhusiano wao ni: waya wa ardhini> laini ya nguvu> laini ya ishara, kawaida upana wa laini ya ishara ni : 0.2 ~ 0.3mm, upana mwembamba zaidi unaweza kufikia 0.05 ~ 0.07mm, laini ya nguvu ni 1.2 ~ 2.5mm kwa ujumla. 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; Mstari wa ishara kupitia shimo inapaswa kuwa kidogo iwezekanavyo;

6. Laini muhimu inapaswa kuwa fupi na nene, na ulinzi pande zote mbili.

Wamiliki wote wa ardhi. When the sensitive signal and noise field signal are transmitted through flat cable, the method of “ground – signal – ground wire” is used.

Leo. 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). Mpya

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

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)

PAD na PAD: ≥0.3mm (12mil)

PADandTRACK: ≥0.3mm (12mil)

TRACKandTRACK: ≥0.3mm (12mil)

Wakati wiani ni mkubwa:

PADandVIA: ≥0.254mm (10mil)

PAD na PAD: ≥0.254mm (10mil)

PADandTRACK: ≥0.254mm (10mil)

TRACKandTRACK: ≥0.254mm (10mil)

Tano: uboreshaji wa wiring na uchapishaji wa skrini. “Hakuna bora zaidi, bora tu”! Haijalishi ni juhudi ngapi unaweka katika muundo, ukimaliza, angalia tena, na bado utahisi unaweza kubadilisha mengi. Utawala wa jumla wa kidole gumba ni kwamba wiring mojawapo inachukua urefu wa wiring mara mbili. Mara tu unapohisi kuwa hakuna kitu kinachohitaji kurekebisha, unaweza Weka shaba. PolygonPlane). Kuweka shaba kwa ujumla kuwekewa waya wa ardhi (zingatia utengano wa ardhi ya analog na dijiti), bodi ya multilayer pia inaweza kuhitaji kuweka nguvu. Kwa uchapishaji wa skrini, tunapaswa kuzingatia usizuiwe na kifaa au kuondolewa kwa shimo na pedi. Wakati huo huo, muundo wa kukabili uso wa sehemu, chini ya neno inapaswa kuwa usindikaji wa vioo, ili usichanganye kiwango.

Sita: kuangalia mtandao na DRC na kuangalia muundo. Kwanza, kwa msingi kwamba muundo wa kielelezo ni sahihi, faili za mtandao za PCB zinazozalishwa na faili za mtandao wa muundo ni NETCHECK ya uhusiano wa uhusiano wa mwili, na muundo huo umerekebishwa kwa wakati kulingana na matokeo ya faili ya pato ili kuhakikisha usahihi wa uhusiano wa uhusiano wa wiring; Baada ya ukaguzi wa mtandao kupitishwa kwa usahihi, hundi ya DRC itafanywa kwenye muundo wa PCB, na muundo utarekebishwa kulingana na matokeo ya faili ya pato kwa wakati ili kuhakikisha utendaji wa umeme wa wiring ya PCB. Mwishowe, muundo wa mitambo ya PCB inapaswa kuchunguzwa zaidi na kuthibitishwa.

Saba: kutengeneza sahani. It is best to have a review process before doing so.

Ubunifu wa PCB ni jaribio la akili ya kazi, ambaye yuko karibu na akili, uzoefu wa hali ya juu, muundo wa bodi ni mzuri. Kwa hivyo muundo unapaswa kuwa mwangalifu sana, uzingatia kabisa mambo ya nyanja zote (kama vile kuwezesha utunzaji na ukaguzi wa hii watu wengi hawafikiria), ubora, utaweza kubuni bodi nzuri.