Wiring of PCB board layout is basic and regular

Must not stick inside 27mm outfit yuan, parts of an apparatus, all round the installing hole such as bolt 3.

5mm (to M2.

5) , 4mm (to M3) inside must not stick assemble yuan of parts of an apparatus or appliance; 3. Lie outfit resistor, inductance (plug-in unit) , electroanalysis the lower part of the component such as capacitance avoids cloth to cross aperture, lest aperture and cell live after wave crest solder housing short circuit; 4. Yuan of parts of an apparatus outside the distance that side is apart from board edge is 5mm; 5. Stick outfit component solder dish outside side and photograph adjacent insert those who assemble element outside side distance is more than 2mm; 6. Metallic housing yuan parts of an apparatus and metal (screen box) cannot with other yuan photograph of parts of an apparatus is touched, cannot clingy print line, solder dish, its span should be more than 2mm. Fixed position aperture, fastener installing hole, elliptical aperture and board in the dimension that the side outside other square aperture is apart from board edge is more than 3mm; 7. Calorific component cannot proximate lead is mixed heat quick component; High fever parts of an apparatus wants balanced distributing; 8. Power source electrical outlet should be decorated as far as possible in printed board all around, power source electrical outlet and the converge that its are linked together terminal should be decorated in with side. Should notice not to want a power source electrical outlet and other solder to receive connector to decorate particularly between connector, with benefit at these electrical outlet, connector solder reach power supply cord to cable is designed and string a line. Power source electrical outlet reachs solder to receive connector decorate what span should consider outlet of convenient power source to insert unplug; 9. Other yuan of parts of an apparatus decorate: Unilateral of all IC component is right neat, designation of polarity component polarity is made clear, designation of the polarity on same printed board does not get two over way, appear when two direction, two direction are mutual and perpendicular; 10, board face wiring should density is proper, should answer when density difference is too big with fill of meshy Copper Foil, reseau is more than 8mil (or 0.

2mm) ; 11, stick a solder dish on cannot have via, lest solder creams,prediction of a person's luck in a given year causes component empty solder. Main line forbids from socket cross between the foot; 12, stick an unilateral to be opposite neat, character direction is consistent, enclose direction to agree; 13, the parts of an apparatus that has polarity is in with same board the polarity designation direction that go up keeps consistent as far as possible. 2, component wiring is regular 1, inside the district that draws calm wiring area to be apart from 1mm of ≤ of PCB board edge, and all round installing hole inside 1mm, prohibit wiring; 2, power supply cord as far as possible wide, do not answer under 18mil; Line is broad do not answer under 12mil; Cpu enters a line not to answer under 10mil (or 8mil) ; Space is apart from not under 10mil; 3, cross aperture normally not under 30mil; 4, biserial inserts continuously: Solder dish 60mil, bore diameter 40mil; 1/4W resistor: 51*55mil (0805 watches are stuck) ; The solder when be being inserted continuously dish 62mil, bore diameter 42mil; Without extremely capacitance: 51*55mil (0805 watches are stuck) ; The solder when be being inserted continuously dish 50mil, bore diameter 28mil; 5, notice power supply cord and ground wire should submit radiative form as far as possible, and line cannot appear answer annulus to take a line. How to enhance interference rejection ability and electromagnetism compatibility? When development brings the electronic product of processor, how to enhance interference rejection ability and electromagnetism compatibility? 1, a few systems below want special attention to fight electromagnetism interference: (1) frequency of small controller clock is particularly tall, the system with bus line particularly fast cycle. (2) the system contains high-power, circuit of drive of big electric current, if produce the relay of scintilla, switch of big electric current. (3) the system that embodies circuit of faint imitate signal and circuit of commutation of high accuracy A/D. 2, it is those who add a system to fight electromagnetism to disturb ability to take following step: (1) choose the small controller with low frequency: The small controller with low frequency of the clock outside choosing can reduce noise and the interference rejection capacity that increase a system effectively. The square wave of same frequency and sine wave, the high frequency component in square wave is more than sine wave much. Although the extent of the wave of the high frequency component of square wave, than base wave is small, but frequency blasts off more easily higher piece become noise source, the most influential high frequency noise that small controller produces is 3 times of clock frequency about. (2) the distortion small controller in reducing signal to transmit basically uses technology of high speed CMOS to make. Signal input carries a static state to input electric current to be controlled in 1mA, input capacitance 10PF left and right sides, input impedance is quite tall, the output end of circuit of high speed CMOS has the belt that comparative to carry ability, comparative to export a worth greatly namely, the output of a door end passes a paragraph very long term bring input impedance quite high input end, reflection problem is very serious, it can cause signal distortion, increase systematic noise. When Tpd " when Tr, became issue of a transmission line, must consider signal reflex, impedance matchs wait for a problem. The characteristic impedance of the defer time on printed board and down-lead concerns signal, the dielectric constant that expects with printed wiring plank namely is concerned. Think roughly, the signal transmission in printed board down-lead speed, the 1 ／ that is velocity of light about 3 to 1 ／ 2 between. The Tr of component of commonly used and logistic phone in the system that small controller makes (standard defer time) for 3 arrive between 18ns. In printed wiring board go up, signal passes the lead with the resistor of a 7W and a paragraph of long 25cm, time of the defer on the line is roughly between 4 ～ 20ns. That is to say, signal is pressworking the down-lead on circuit is shorter better, the longest unfavorable exceed 25cm. And cross opening number to also answer as far as possible little, had better not 2 over. The rise time when signal is fast at signal defer time, be about to be handled according to fast electronics. The impedance that should consider transmission line right now matchs, to pressworking together the collect on circuit board is agglomerate the signal between is transmitted, should avoid occurrence Td " the circumstance of Trd, presswork the rate that circuit board exceeds old system is jumped over cannot too fast. Induce with the following conclusion presswork a regulation that circuit board designs: Signal is pressworking board upload be defeated, what its defer time should not be more than place to use parts of an apparatus is nominal defer time. (3) the alternant interference that reduces signal space: A nods a rise time to be Tr rank jump signal to be passed to B end through down-lead AB. Signal is in time of AB on-line defer is Td. In D dot, because be transmitted of A dot signal ahead, arrive at the defer of the signal reflex after B is nodded and AB line, meeting induction gives a width to be the page pulse signal of Tr after Td time. In C dot, as a result of the transmission of the signal on AB and reflex, meeting induction gives a width to be in for signal double of time of AB on-line defer, namely of 2Td pulse signal. This is the alternant interference between signal. The intensity that disturbs signal and the Di/at that C nods signal are concerned, with space the distance is concerned. When two line not be very long when, what see on AB is actual the alternate that is two pulse is added. The small control that CMOS craft makes by the input impedance is tall, noise is loud, noise tolerance is very tall also, digital circuit is alternate adds noise of 100 ～ 200mv not to affect its to work. If line of the AB in the graph is one imitate signal, this kind of interference turns into flagrant. If presswork,circuit board is 4 layer board, have a land that is large area among them, or double face plate, when the ground that the opposite of line is large area, the alternate interference between this kind of signal is met decrescent. The reason is, the ground of large area reduced the characteristic impedance of line, the reflex that signal carries in D is reduced greatly. Characteristic impedance and line become inverse ratio to the square of the dielectric constant of the medium between the ground, become direct ratio with the natural logarithm of medium ply. If AB line is one imitate signal, should shun digital circuit line the CD interference to AB, AB line lower part should have the land of large area, the 2 ～ that AB line wants to be more than AB line and ground distance to the distance of CD line 3 times. Can use local screen land, in the one side catalyst that makes a written guarantee controls two side cloth with ground wire. (4) reduce the noise that comes from power source while power source is providing the sources of energy to the system, also add its noise to the power source of place power supply. The restoration line of small controller in circuit, break a string, and a few control line get other the most easily the interference of outside noise. The strong interference on electrified wire netting enters circuit through power source, although the system of batteries power supply, batteries itself also has high frequency noise. The imitate signal in imitate circuit more do not endure the interference that comes from power source. (5) the attention pressworks line board and yuan the high frequency character of parts of an apparatus falls in high frequency circumstance, presswork the down-lead on circuit board, cross aperture, the distributinging inductance that receives plug-in unit and resistor, capacitance, capacitance cannot oversight. The distributinging inductance of capacitance cannot oversight, the distributinging capacitance of inductance cannot oversight. Resistor produces the reflex of pair of high frequency signal, the distributinging capacitance of down-lead will be effective, when the 1/20 that is more than noise frequency to lead corresponding wavelengh when length, produce aerial effect, noise blasts off outwards through down-lead. Presswork of circuit board cross aperture to be caused about 0.

The capacitance of 6pf. Of itself of an integrated circuit enclose material to introduce capacitance of 2 ～ 6pf. On a circuit board receive plug-in unit, have the distributinging inductance of 520nH. A short slender pointed piece of metal of the 24 integrated circuit that cite a base of straight a short slender pointed piece of metal of a biserial, introduce the distributinging inductance of 4 ～ 18nH. It is negligible in the small controller system that these small distributinging parameter leave to this inferior frequency not plan; And must give to high speed system special attention. (6) component is decorated want reasonable partition component is pressworking the place that arranges on circuit board wants mature fight electromagnetism to disturb a problem, one of principles are the down-lead between each component wants as far as possible short. On layout, want an imitate signal part, part of circuit of high speed number, noise cause share (be like relay, switch of big electric current) this 3 parts part reasonably, make mutual the signal coupling between is the smallest. G handles good ground wire: Printed circuit board go up, power supply cord and ground wire are the most important. Overcome electromagnetism interference, the mainest measure is ground connection. To double face plate, ground wire is decorated particularly exquisite, choose ground connection magic art through using sheet, power source and ground are the two termination from power source arrive presswork circuit board comes up, power source a contact, the ground a contact. Presswork on circuit board, want to many return ground wire, these metropolises get together to go up to that contact of wire back source, it is ground contact of alleged sheet spot. Ground of alleged imitate ground, number ground, high-power parts of an apparatus opens branch, it is to show wiring is apart, and finally the assemble receives a place to come up to this. With presswork when the signal beyond circuit board is linked together, use screen cable normally. To high frequency with digital signal, screen cable two end ground connection. The screen cable that signal of low frequency imitate uses, ground connection of one aspect of the matter had better. The circuit with very sensitive to noise and interference circuit or high frequency particularly serious noise should overspread screen to rise with the metal. (7) had used go Ou capacitance. Good high frequency go Ou capacitance is OK purify arrives high the high frequency component of 1GHZ. Contented ceramics capacitance or multilayer the high frequency character of capacitance of pottery and porcelain is better. The design pressworks when circuit board, the power source of every integrated circuit, one should be added to go between the ground Ou capacitance. Go Ou capacitance has two effect: The harbour that is this integrated circuit on one hand can capacitance, offer and absorb this integrated circuit to open the door close of the instant charge discharge can; On the other hand bypass drops the high frequency noise of this parts of an apparatus. Ou capacitance goes typically in digital circuit for 0.

Of 1uf go Ou capacitance has 5nH distributinging inductance, its collateral resonance frequency is controlled in 7MHz about, it is better to have to the noise under 10MHz that is to say go Ou action, act well scarcely to the noise of 40MHz above. 1uf, 10uf capacitance, collateral resonance frequency is in 20MHz above, the effect of noise of purify tall frequency is close friends a few. Enter in power source presswork board of place and a 1uf or 10uf go high frequency capacitance often is advantageous, even if the system that uses batteries power supply also needs this kind of electric capacity. Every 10 right-and-left integrated circuit should add to fill discharge electric capacity, or call harbour to put electric capacity, capacitance size is optional 10uf. Had better not use electroanalysis capacitance, electroanalysis two broading film coil capacitance, this kind of structure that coils is in high frequency when expression is inductance, had better use bravery electric capacity or get together capacitance of carbonic acid Yun. Go to what Ou capacitance is worth choosing lax case, can press computation of C ＝ 1/f; Namely 10MHz is taken 0.

1uf, to the system that small controller makes, take 0.

1 ～ 0.

Between 01uf OK. 3, a few experience that reduce noise and electromagnetism interference. (1) can use low speed chip need not high-speed, high speed chip is used in crucial place. (2) can use the method that strings together a resistor, reduce edge of control circuit fluctuation to jump gearshift rate. (3) wait for the damp that offers some kind of form for relay as far as possible. (4) the lowermost frequency clock that uses contented system requirement. (5) clock generator draws near as far as possible the parts of an apparatus that uses this clock. Crystal oscillator crust wants quartz ground connection. (6) rise clock area circle with ground wire, clock line as far as possible short. (7) I/O drive circuit as far as possible ＊ pressworks nearly board edge, let its leave as soon as possible presswork board. Want to add filter wave to entering the signal of printed board, the signal that comes from loud noise area also should add filter wave, use the method that strings together terminal resistor at the same time, reduce signal reflex. (8) end of MCD no use should be received tall, or ground connection, or the definition is carried into output, this receives power source land end on integrated circuit wants to receive, not impending. (9) door circuit input carries unused unused not impending, carry puts unused unused to inputting termination ground, negative input termination outputs end. (10) printed board uses 45 broken line as far as possible and need not wiring of 90 broken line in order to reduce high frequency signal external blast off with coupling. (11) printed board presses frequency and partition of voltaic switch character, noise component and blame noise component should are apart from again a few further. (12) odd face plate and double face plate receive power source and only place ground contact, power supply cord, ground wire with only place as far as possible thick, economy is if can bearing, use multilayer board in order to reduce power supply, the look of the ground gives birth to inductance. (13) clock, bus line, piece choose signal to want to be far from I/O line and receive plug-in unit. (14) end of line of imitate voltage input, referenced voltage should be far from digital circuit line as far as possible, especially clock. (15) to A/D kind parts of an apparatus, digital part and imitate part would rather be united fall to also do not want across. (16) clock line is perpendicular disturb than parallel I/O line at I/O line small, clock component brings a foot to be far from I/O cable. (17) component cites a base as far as possible short, go Ou capacitance cites a base as far as possible short. (18) crucial line wants as far as possible thick, add protective land in both sides. High speed line wants short should straight. (19) sensitive to noise line does not want with big electric current, line of high speed switch is parallel. (20) quartz below crystal and the line does not take below sensitive to noise parts of an apparatus. (21) weak signal circuit, voltaic annulus way is not formed all round low frequency circuit. (22) any signal do not form annulus way, be like inevitable, district of district letting ring as far as possible small. (23) every integrated circuit goes Ou capacitance. Every electroanalysis an electric capacity of small high frequency bypass should be increased on capacitance edge. (24) the tantalum electric capacity that uses high capacity or get together cruel capacitance and need not electroanalysis capacitance makes circuit charge discharge store can capacitance. When using electric capacity tubal account, crust wants ground contact. CNC Milling