Circuit design skills PCB design process

General PCB basic design process is as follows: preliminary preparation – >; PCB structure design -& GT; Qaabka PCB – & GT; Fiilooyinka – & GT; Hagaajinta waddada iyo daabacaadda shaashadda -> 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. Mabda ‘ahaan, marka hore samee maktabadda qaybaha PCB, ka dibna maktabadda qaybaha SCH. Shuruudaha maktabadda qaybaha PCB ayaa sarreeya, waxay si toos ah u saamaysaa rakibidda guddiga; Shuruudaha maktabadda qaybaha SCH waa kuwo dabacsan, ilaa inta fiiro gaar ah la siinayo qeexidda sifooyinka biinka iyo xiriirka u dhigma qaybaha PCB. PS: Note the hidden pins in the standard library. Kadibna waa naqshadda qaab -dhismeedka, oo diyaar u ah samaynta naqshadda PCB.

Midda labaad: Naqshadaynta qaab -dhismeedka PCB. Tallaabadan, marka loo eego cabbirka guddiga wareegga iyo meelaynta farsamada, dusha guddiga PCB waxaa lagu sawiraa bay’ada naqshadeynta PCB, iyo isku xirayaasha, badhamada/furayaasha, daloolada fur, godadka shirarka iyo wixii la mid ah ayaa la dhigayaa iyadoo la raacayo shuruudaha meelaynta. 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).

Saddexaad: Qaab -dhismeedka 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), ka dibna soo deji miiska shabakadda shaxanka PCB (design-gt; LoadNets). Fiiri hubbub aaladda qalabka oo dhan, inta u dhexeysa biinanka iyo isku xirka degdegga ah ee duulimaadka. Waxaad markaa dhigi kartaa qalabka. Qaab -dhismeedka guud waxaa loo fuliyaa si waafaqsan mabaadi’da soo socota:

(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; Qaybta kululaynta waa in laga soocaa walxaha xasaasiga ah ee heerkulka, haddii loo baahdana, waa in la tixgeliyaa tallaabooyinka kuleylka kuleylka;

(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); Awoodda tantalum -ka ayaa sidoo kale lagu dhejin karaa dhowr wareeg oo isku dhafan marka booska guddiga wareegga uu yahay mid adag.

Dhammaan milkiilayaasha dhulka. Relay coil to add discharge diode (1N4148 can be);

Maanta. 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.

Ta afaraad: xarig. Fiilooyinka waa habka ugu muhiimsan ee naqshada PCB. Tani waxay si toos ah u saamayn doontaa waxqabadka guddiga PCB. Geedi socodka naqshadaynta PCB, xariggu guud ahaan wuxuu leeyahay saddex heer oo kala qaybin ah: midda koowaad waa qaybinta, taas oo ah shardiga ugu muhiimsan ee naqshadda 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. Tani waa halbeegga lagu cabbiro in guddiga wareegga daabacan uu u qalmo iyo in kale. This is after the distribution, carefully adjust the wiring, so that it can achieve the best electrical performance. Markaas waxaa jira bilicsanaanta. Haddii maradaada fiilooyinka ay ku xirnayd, sidoo kale ma haysato meesha ay saameyneyso wax -qabadka qalabka korontada, laakiin u fiirso sidii hore, si dar -dar leh u dar, ku dar midabo, midabo dhalaalaya, oo xisaabiya sida wax -qabadka qalabka korontadu u fiican yahay, weli qashin ku noqo indhaha dadka kale. This brings great inconvenience to testing and maintenance. Fiilooyinka waa in ay ahaadaan kuwo hagaagsan oo lebisan, oo aan qallafsanayn sharci la’aan. Waxaas oo dhan waa in lagu gaaraa macnaha guud ee hubinta waxqabadka korantada iyo buuxinta shuruudaha shaqsiyeed ee kale, haddii kale waa in laga tagaa nuxurka. Fiilooyinka waa in loo fuliyaa si waafaqsan mabaadi’da soo socota:

(1). Guud ahaan, fiilada korontada iyo fiilada dhulka waa in marka hore la leexiyaa si loo hubiyo waxqabadka korontada ee guddiga wareegga. Baaxadda ay xaaladdu oggolaaneyso, ballaarinta ballaarinta korontada, siligga dhulka inta ugu badan ee suurtogalka ah, waxaa ugu wanaagsan in siligga dhulka uu ka ballaaran yahay xarigga korantada, xiriirkoodu waa: siligga dhulka> xarigga korontada> xariijinta signalada, badiyaa xarriiqda calaamadda : 0.2 ~ 0.3mm, ballaca ugu khafiifsan wuxuu gaari karaa 0.05 ~ 0.07mm, khadka korontadu waa 1.2 ~ 2.5mm guud ahaan. 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; Laynka calaamadda ee daloolka waa inuu ahaadaa mid aad u yar intii suurtogal ah;

6. Laynka muhiimka ahi waa inuu ahaadaa mid gaaban oo qaro weyn leh, oo labada dhinacba laga ilaalinayo.

Dhammaan milkiilayaasha dhulka. When the sensitive signal and noise field signal are transmitted through flat cable, the method of “ground – signal – ground wire” is used.

Maanta. 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). line

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

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)

Marka cufnaanta ay sareyso:

PADandVIA: ≥0.254mm (10mil)

PADandPAD: ≥0.254mm (10mil)

PADandTRACK: ≥0.254mm (10mil)

TRACKandTRACK: ≥0.254mm (10mil)

Shanaad: tayaynta fiilooyinka iyo daabacaadda shaashadda. “Ma jiro wax fiican, kaliya ayaa ka fiican”! Si kasta oo aad dadaal ugu gasho nashqadda, markaad dhammayso, mar kale fiiri, oo waxaad weli dareemi doontaa inaad wax badan beddeli karto. Xeerka naqshadda guud ee suulka ayaa ah in xarigga ugu fiicani uu qaato laba jeer inta kaararka hore. Markaad dareento inaanay waxba u baahnayn hagaajin, waxaad dhigi kartaa naxaas. PolygonPlane). Dhigista naxaas guud ahaan dhigaysa silig dhulka (fiiro gaar ah u leh kala -soocidda dhulka analoogga iyo dhijitaalka ah), guddiga badan ayaa sidoo kale laga yaabaa inay u baahdaan inay awoodda dhigaan. Daabacaadda shaashadda, waa inaan fiiro gaar ah u yeelanno in aaladdu aysan xannibin ama aan ka qaadin daloolka iyo suufka. Isla mar ahaantaana, naqshadeynta si aad u wajahdo dusha sare ee qeybta, erayga hoostiisa waa inuu noqdaa muraayad, si uusan u jahwareerin heerka.

Lixaad: hubinta shabakadda iyo DRC iyo hubinta qaab -dhismeedka. Marka hore, iyada oo laga duulayo in naqshadda qaab -dhismeedku ay sax tahay, faylasha shabakadda PCB ee la soo saaray iyo feylasha shabakadda ee mashruuca ayaa ah NETCHECK xiriirka xiriirka jirka, iyo naqshadeynta ayaa waqtigeeda wax laga beddelay iyadoo la raacayo natiijooyinka faylka soo -saarka si loo hubiyo saxnimada xiriirka isku xirka fiilooyinka; Ka dib marka jeegga shabakadda si sax ah loo gudbiyo, jeegga DRC waxaa lagu fulin doonaa naqshadda PCB, iyo naqshadeynta ayaa wax laga beddeli doonaa iyadoo la raacayo natiijooyinka faylka soo -saarka waqtiga si loo hubiyo waxqabadka korantada ee fiilooyinka PCB. Ugu dambayn, qaab -dhismeedka rakibidda farsamada ee PCB waa in la sii hubiyo oo la xaqiijiyaa.

Toddobaad: samaynta saxan. It is best to have a review process before doing so.

Naqshadeynta PCB waa imtixaanka maskaxda shaqada, yaa u dhow maskaxda, waayo -aragnimada sare, naqshadda guddiga ayaa wanaagsan. Markaa naqshadu waa inay aad u taxaddartaa, si buuxda u tixgelisaa qodobbada dhammaan dhinacyada (sida fududeynta dayactirka iyo kormeerka tan dad badan ma tixgeliyaan), heer sare, waxay awoodi doonaan inay naqshadeeyaan guddi wanaagsan.