bruidhinn PCB bòrd, many friends will think that it can be seen everywhere around us, from all household appliances, all kinds of accessories in the computer, to all kinds of digital products, as long as electronic products almost all use PCB board, so what is PCB board? A PCB is a PrintedCircuitBlock, which is a printed circuit board for electronic components to be inserted. A copperplated base plate is printed and etched out of the etching circuit.

Faodar bòrd PCB a roinn ann am bòrd aon shreath, bòrd còmhdach dùbailte agus bòrd ioma-fhilleadh. Tha pàirtean dealanach air am filleadh a-steach don PCB. Air PCB aon-fhillte bunaiteach, tha na pàirtean air an cuimseachadh air aon taobh agus tha na uèirichean stèidhichte air an taobh eile. Mar sin feumaidh sinn tuill a dhèanamh sa bhòrd gus an urrainn dha na prìnichean a dhol tron ​​bhòrd chun taobh eile, gus am bi prìnichean nam pàirtean air an tàthadh chun taobh eile. Because of this, the positive and negative sides of such PCB are respectively called ComponentSide and SolderSide.

A double-layer board can be seen as two single-layer boards glued together, with electronic components and wiring on both sides of the board. Aig amannan feumar aon uèir a cheangal bho aon taobh gu taobh eile a ’bhùird tro tholl treòrachaidh (via). Tha tuill treòrachaidh nan tuill bheaga anns a ’PCB air an lìonadh no air an còmhdach le meatailt a dh’ fhaodar a cheangal ri uèirichean air gach taobh. A-nis tha mòran de motherboards coimpiutair a ’cleachdadh 4 no eadhon 6 sreathan de bhòrd PCB, fhad‘ s a bhios cairtean grafaiceachd mar as trice a ’cleachdadh 6 sreathan de bhòrd PCB. Bidh mòran de chairtean grafaigeach àrd mar sreath nVIDIAGeForce4Ti a ’cleachdadh 8 sreathan de bhòrd PCB, ris an canar bòrd PCB ioma-fhilleadh. The problem of connecting lines between layers is also encountered on multi-layer PCBS, which can also be achieved through guide holes.

Leis gur e PCB ioma-fhilleadh a th ’ann, uaireannan chan fheum na tuill treòrachaidh a dhol a-steach don PCB gu lèir. Canar Buriedvias agus Blindvias ri tuill treòrachaidh mar sin oir chan eil iad a ’dol ach beagan shreathan. Bidh tuill dall a ’ceangal grunn shreathan de PCBS a-staigh gu uachdar PCBS gun a bhith a’ dol tron ​​bhòrd gu lèir. Chan eil tuill tiodhlaichte ceangailte ach ris a ’PCB a-staigh, agus mar sin chan eil solas ri fhaicinn bhon uachdar. Ann am PCB multilayer, tha an còmhdach gu lèir ceangailte gu dìreach ris an uèir talmhainn agus an solar cumhachd. Mar sin bidh sinn a ’seòrsachadh nan sreathan mar Chomharran, Cumhachd no Grunnd. Ma dh ’fheumas na pàirtean air a’ PCB solar cumhachd eadar-dhealaichte, mar as trice bidh barrachd air dà shreath cumhachd is uèir aca. The more layers you use, the higher the cost. Of course, the use of more layers of PCB board to provide signal stability is very helpful.

The process of making a professional PCB board is quite complicated. Take a 4-layer PCB board for example. Tha PCB a ’phrìomh bhòrd mar as trice 4 sreathan. Nuair a thathar a ’saothrachadh, tha an dà shreath mheadhain air an roiligeadh, air an gearradh, air an seargadh, air an oxidachadh agus air an dealanachadh. Is e na ceithir sreathan uachdar co-phàirteach, còmhdach cumhachd, stratum agus lamination solder fa leth. Bidh na ceithir sreathan an uairsin air am brùthadh còmhla gus PCB a chruthachadh airson a ’phrìomh bhòrd. Then the holes were punched and made. An dèidh a ghlanadh, tha an dà shreath a-muigh den loidhne air a chlò-bhualadh, copar, searbhagachd, deuchainn, còmhdach an aghaidh tàthadh, clò-bhualadh sgrion. Mu dheireadh, tha am PCB gu lèir (a ’toirt a-steach mòran de motherboards) air a stampadh a-steach do PCB de gach motherboard, agus an uairsin thèid pasgan falamh a dhèanamh às deidh dhaibh a dhol seachad air an deuchainn. If the copper skin is not well coated in THE process of PCB production, there will be poor adhesion phenomenon, easy to imply short circuit or capacitance effect (easy to cause interference). The holes on PCB must also be taken care of. If the hole is punched not in the middle, but on one side, it will result in uneven matching or easy contact with the power supply layer or formation in the middle, resulting in potential short-circuiting or bad grounding factors.

Copper wiring process

The first step in fabrication is to establish an online wiring between parts. We use negative transfer to express the working negative on a metal conductor. Is e an cleas a bhith a ’sgaoileadh sreath tana de foil copair thairis air an uachdar gu lèir agus a’ toirt air falbh cus. Is e dòigh eile nach eilear a ’cleachdadh gluasad a tha a’ cur a-steach gluasad, is e sin uèir copar a chuir an sàs a-mhàin far a bheil feum air, ach cha bhith sinn a ’bruidhinn mu dheidhinn an seo.

Positive photoresists are made from photosensitizers that dissolve under illumination. There are many ways to treat photoresist on copper, but the most common way is to heat it and roll it over a surface containing photoresist. It can also be sprayed in liquid form, but the dry film provides higher resolution and allows for thinner wires. Is e dìreach teamplaid a th ’anns a’ chochall airson sreathan PCB a dhèanamh. Bidh cochall a tha a ’còmhdach an photoresist air a’ PCB a ’cur casg air cuid de raointean den photoresist a bhith fosgailte gus am bi an photoresist fosgailte do sholas UV. These areas, which are covered with photoresist, will become wiring. Pàirtean copair lom eile ri sgrìobadh às deidh leasachadh photoresist. The etching process may involve dipping the board into the etching solvent or spraying the solvent onto the board. Mar as trice air a chleachdadh mar fhuasglaiche searbhachaidh a ’cleachdadh ferric chloride msaa. After etching, remove the remaining photoresist.

1. Leud uèir agus sruth

General width should not be less than 0.2mm (8mil)

On high density and high precision PCBS, pitch and line width are generally 0.3mm (12mil).

Nuair a tha tiugh foil copair mu 50um, is e leud an uèir 1 ~ 1.5mm (60mil) = 2A

Tha an talamh cumanta mar as trice 80mil, gu sònraichte airson tagraidhean le microprocessors.

2. Dè cho àrd ‘sa tha tricead bòrd àrd-astar?

Nuair a dh ’èireas / a thuiteas ùine a’ chomharra “3 ~ 6 uiread na h-ùine tar-chuir comharran, tha e air a mheas mar chomharradh aig astar àrd.

Airson cuairtean didseatach, is e an iuchair sùil a thoirt air cas cas an comharra, an ùine a bheir e gus èirigh is tuiteam,

According to a very classic book “High Speed Digtal Design” theory, the signal from 10% to 90% of the time is less than 6 times the wire delay, is high-speed signal! – – – – – – eadhon! Even 8KHz square wave signals, as long as the edges are steep enough, are still high-speed signals, and transmission line theory needs to be used in wiring

3.PCB a ’cruachadh agus a’ laighe

The four – layer plate has the following stacking sequence. Tha na buannachdan agus na h-eas-bhuannachdan bho dhiofar lamination air am mìneachadh gu h-ìosal:

Bu chòir a ’chiad chùis a bhith mar as fheàrr de na ceithir sreathan. Because the outer layer is the stratum, it has a shielding effect on EMI. Meanwhile, the power supply layer is reliable and close to the stratum, which makes the internal resistance of the power supply smaller and achieves the best suburbs. Ach, chan urrainnear a ’chiad chùis a chleachdadh nuair a tha dùmhlachd a’ bhùird an ìre mhath àrd. Air sgàth sin, chan eil ionracas a ’chiad shreath air a ghealltainn, agus tha an comharra dàrna còmhdach nas miosa. In addition, this structure can not be used in the case of large power consumption of the whole board.

The second case is the one we usually use the most. Bho structar a ’bhùird, chan eil e freagarrach airson dealbhadh cuairteachadh didseatach aig astar àrd. Tha e duilich bacadh le cumhachd ìosal a chumail suas san structar seo. Take a plate 2 mm as an example: Z0=50ohm. To line width of 8mil. Copper foil thickness is 35цm. Mar sin is e an ìre comharra agus meadhan an cruthachadh 0.14mm. The formation and power layer are 1.58mm. This greatly increases the internal resistance of the power supply. In this kind of structure, because the radiation is to the space, shielding plate is needed to reduce EMI.

In the third case, the signal line on layer S1 has the best quality. S2. Sgiath EMI. But the power supply impedance is large. This board can be used when the power consumption of the whole board is high and the board is an interference source or adjacent to the interference source.

4. Impedance matching

Tha meud an comharra bholtachd meòrachail air a dhearbhadh le co-èifeachd meòrachaidh stòr ρ S agus co-èifeachd meòrachaidh an luchd ρL

ρL = (RL-z0)/(RL + Z0) and ρS = (rS-z0)/(RS + Z0)

Anns a ’cho-aontar gu h-àrd, ma tha RL = Z0, an co-èifeachd meòrachaidh luchdan ρL = 0. Ma tha co-èifeachd meòrachaidh deireadh stòr RS = Z0 ρS = 0.

Leis gum bu chòir an impedance loidhne sgaoilidh àbhaisteach Z0 mar as trice coinneachadh ri riatanasan 50 ω 50 ω, agus mar as trice tha am bacadh luchdan ann am mìltean de ohms gu deichean de mhìltean de ohms. Mar sin, tha e duilich maids impedance a thoirt gu buil aig taobh an luchd. However, because the signal source (output) impedance is usually relatively small, roughly in the tens of ohms. Mar sin tha e mòran nas fhasa maids bacadh a chuir an gnìomh aig an stòr. If a resistor is connected at the load end, the resistor will absorb part of the signal to the detriment of transmission (my understanding). Nuair a thèid sruth dràibhidh 24mA àbhaisteach TTL / CMOS a thaghadh, tha am bacadh toraidh timcheall air 13 ω. If the transmission line impedance Z0=50 ω, then a 33 ω source-end matching resistor should be added. 13 ω +33 ω = 46 ω (timcheall air 50 ω, bidh fo-fhilleadh lag a ’cuideachadh ùine rèiteachaidh chomharran)

Nuair a thèid inbhean tar-chuir eile agus sruthan dràibhidh a thaghadh, faodaidh am bacadh co-fhreagarrach a bhith eadar-dhealaichte. Ann an loidsig àrd-astar agus dealbhadh cuairteachaidh, airson cuid de phrìomh chomharran, leithid gleoc, comharran smachd, tha sinn a ’moladh gum feumar an resistor maidsidh stòr a chur ris.

San dòigh seo, thèid an comharra ceangailte a nochdadh air ais bho thaobh an luchd, oir tha an impedance stòr a ’maidseadh, cha tèid an comharra meòrachail a nochdadh air ais.