What is line width?

Ka anyi bido site na isi. What exactly is trace width? Kedu ihe kpatara o ji dị mkpa kapịpị obosara ọnụọgụ ọnụọgụ? Nzube nke PCB wiring bụ ijikọ ụdị mgbaàmà eletriki ọ bụla (analog, dijitalụ ma ọ bụ ike) site n’otu ọnụ gaa n’ọzọ.

Otu ọnụ nwere ike ịbụ ntụtụ nke ihe mejupụtara ya, ngalaba nke nnukwu trace ma ọ bụ ụgbọ elu, ma ọ bụ paịlị efu ma ọ bụ ebe nnwale maka nyocha. Trace widths are usually measured in mils or thousands of inches. Standard wiring widths for ordinary signals (no special requirements) may be several inches in length in the 7-12 mils range, but many factors should be considered when defining the wiring width and length.

The application typically drives the wiring width and wiring type in PCB design and, at some point, usually balances PCB manufacturing cost, board density/size, and performance. Ọ bụrụ na bọọdụ ahụ nwere ihe nrụpụta akọwapụtara nke ọma, dị ka njikarịcha ọsọ ọsọ, mkpọtụ ma ọ bụ iwepụ njikọ, ma ọ bụ nnukwu ọkụ eletrik/obosara/obosara, ịdị obosara na ụdị nke trace nwere ike ịdị mkpa karịa iwepụta ọnụahịa nrụpụta PCB efu ma ọ bụ nha bọọdụ n’ozuzu ya.

Specification relating to wiring in PCB manufacturing

Dịka, nkọwa ndị a metụtara wiwi na -amalite ịbawanye ọnụ ahịa n’ichepụta PCBS efu.

N’ihi nnabata PCB siri ike yana akụrụngwa dị elu achọrọ maka nrụpụta, nyocha ma ọ bụ nnwale nke PCBS, ọnụ ahịa na-adị oke elu:

L Chọpụta obosara erughị mil 5 (0.005 in.)

L Trace spacing less than 5 mils

L Through holes less than 8 mil in diameter

L Trace ọkpụrụkpụ na -erughị ma ọ bụ hà nhata 1 ounce (hà nhata 1.4 mils)

L Differential pair and controlled length or wiring impedance

Ọdịdị njupụta dị elu nke na-ejikọ ohere PCB, dị ka BGA sara mbara nke ukwuu ma ọ bụ ọnụ ọgụgụ ụgbọ ala yiri mgbaaka, nwere ike ịchọ ahịrị ahịrị nke mil 2.5, yana ụdị oghere pụrụ iche nwere dayameta nke ruru mil 6, dị ka laser gbapuru microthrough-oghere. N’aka nke ọzọ, ụfọdụ atụmatụ ike dị elu nwere ike ịchọ wired ma ọ bụ ụgbọ elu buru ibu, na-eri akwa niile ma na-awụsa ounces ndị buru ibu karịa ọkọlọtọ. In space-constrained applications, very thin plates containing several layers and a limited copper casting thickness of half an ounce (0.7 mil thickness) may be required.

N’ọnọdụ ndị ọzọ, atụmatụ maka nkwukọrịta ọsọ ọsọ site na mpụta ya gaa na nke ọzọ nwere ike ịchọ wiwi nwere impedance a na-achịkwa yana obosara akọwapụtara na oghere n’etiti ibe ha iji belata echiche na njikọta ihe. Ma ọ bụ imewe nwere ike ịchọ ogologo ka o kwekọọ na akara ndị ọzọ dị mkpa n’ime bọs. Ngwa ngwa ọkụ dị elu chọrọ njirimara nchekwa ụfọdụ, dị ka ibelata ohere dị n’etiti akara ngosi abụọ dị iche iche ekpughere iji gbochie arcing. Na agbanyeghị njirimara ma ọ bụ njirimara, nkọwapụta dị mkpa, yabụ ka anyị nyochaa ngwa dị iche iche.

Various wiring widths and thicknesses

PCBS na -enwekarị ahịrị ahịrị dị iche iche, ebe ọ dabere na ihe mgbaàmà chọrọ (lee Ọgụgụ 1). Ihe kachasị dị mma egosipụtara bụ maka ebumnuche TTL n’ozuzu (transistor-transistor logic) na enweghị ọkwa pụrụ iche maka nchekwa dị elu ma ọ bụ mkpọtụ.

Ndị a ga -abụ ụdị wiring kachasị na bọọdụ.

Ewelitela wiwi dị arọ maka ikike iburu ugbu a, enwere ike iji ya maka akụkụ ma ọ bụ ọrụ metụtara ike nke chọrọ ike dị elu, dị ka ndị na-akwado fan, moto, na nnyefe ike oge niile na ihe ndị dị ala. The upper left part of the figure even shows a differential signal (USB high-speed) that defines a specific spacing and width to meet the impedance requirements of 90 ω. Ọgụgụ 2 na -egosi bọọdụ sekit dị warara nke nwere ọkwa isii ma chọọ mgbakọ BGA (grid grid array) nke chọrọ eriri kacha mma.

How to calculate PCB line width?

Let’s step through the process of calculating a certain trace width for a power signal that transfers current from a power component to a peripheral device. N’ihe atụ a, anyị ga -agbakọọ obosara ahịrị kacha nta nke ụzọ ike maka moto DC. Ụzọ ike na-amalite na fuuz, gafee H-bridge (akụrụngwa ejiri jikwaa nnyefe ike n’ofe windo moto DC), wee kwụsị na njikọ nke moto ahụ. Nkezi na -aga n’ihu kacha ugbu a nke moto DC chọrọ bụ ihe dịka ampe abụọ.

Ugbu a, wiwi PCB na -arụ ọrụ dị ka onye na -emegide ya, ogologo oge na warara ka a na -etinyekwu ihe mgbochi. If wiring is not defined correctly, the high current may damage wiring and/or cause a significant voltage drop to the motor (resulting in reduced speed). The NetC21_2 shown in Figure 3 is about 0.8 inches long and needs to carry a maximum current of 2 amperes. Ọ bụrụ na anyị ewere ọnọdụ ụfọdụ n’ozuzu, dị ka 1 ounce ọla kọpa wụsara na okpomọkụ ụlọ n’oge arụ ọrụ nkịtị, ọ dị anyị mkpa ịgbakọ obosara ahịrị kacha nta na mgbali atụ anya na mgbada ahụ.

Kedu otu esi gbakọọ nkwụnye ọkụ PCB?

The following equation is used for trace area:

Area [Mils ²] = (current [Amps] / (K * (Temp_Rise [°C]) ^ b)) ^ (1 / C), which follows IPC outer layer (or top/bottom) criterion, k = 0.048, b = 0.44, C = 0.725. Rịba ama na naanị mgbanwe anyị kwesịrị itinye bụ nke ugbu a.

Using this region in the following equation will give us the necessary width that tells us the line width needed to carry the current without any potential problems:

Obosara [Mils] = mpaghara [Mils ^ 2] / (ọkpụrụkpụ [oz] * 1.378 [mils / oz]), ebe 1.378 metụtara ọkọlọtọ 1 oz na -awụsa ọkpụrụkpụ.

Site na ịtinye amperes abụọ dị ugbu a na ngụkọta a dị n’elu, anyị na -enweta opekata mpe nke mils 2.

Mana nke ahụ anaghị agwa anyị ihe mgbada ọkụ ga -abụ. This is more involved because it needs to calculate the resistance of the wire, which can be done according to the formula shown in Figure 4.

N’ime usoro a, ρ = resistivity nke ọla kọpa, α = ọnụọgụ ọnụọgụ ọla kọpa, T = trace ọkpụrụkpụ, W = Chọpụta obosara, L = ogologo akara, T = okpomoku. Ọ bụrụ na etinyere ụkpụrụ niile dị mkpa n’ogo 0.8 “ogologo nke 30mils obosara, anyị na -achọpụta na mgbochi wiring bụ ihe dịka 0.03? And it lowers the voltage by about 26mV, which is fine for this application. Ọ bara uru ịmara ihe na -emetụta ụkpụrụ ndị a.

PCB cable spacing na ogologo

Maka atụmatụ dijitalụ nwere nkwukọrịta ọsọ ọsọ, enwere ike ịchọ oghere dị iche na ogologo ahaziri iji belata crosstalk, njikọ, na ntụgharị uche. Maka ebumnuche a, ụfọdụ ngwa a na-ahụkarị bụ akara ngosipụta dị iche iche nke eriri USB na akara ngosi ọdịiche yiri nke dabere na RAM. Typically, USB 2.0 will require differential routing at 480Mbit/s (USB high speed class) or higher. This is partly because high-speed USB typically operates at much lower voltages and differences, bringing the overall signal level closer to background noise.

There are three important things to consider when routing high-speed USB cables: wire width, lead spacing, and cable length.

Ihe ndị a niile dị mkpa, mana nke kacha akatọ n’ime atọ bụ ijide n’aka na ogologo ahịrị abụọ dabara nke ọma. As a general rule of thumb, if the lengths of the cables differ from each other by no more than 50 mils (for high-speed USB), this significantly increases the risk of reflection, which may result in poor communication. 90 ohm impedance dakọtara bụ nkọwapụta izugbe maka ụzọ abụọ dị iche iche. Iji mezuo ebumnuche a, ekwesịrị ịkwalite ụzọ ụgbọ ala n’obosara na oghere.

Ọgụgụ 5 na-egosi ihe atụ nke ụzọ abụọ dị iche iche maka ịgbanye eriri USB nwere oke ọsọ nke nwere eriri elekere 12 mil na etiti nkeji iri na ise.

Ntanetị maka ihe ndị dabere na ebe nchekwa nke nwere oghere yiri ya (dịka DDR3-SDRAM) ga-amachibido n’ihe gbasara ogologo waya. Imirikiti sọftụwia imewe PCB ga-enwe ike nhazigharị ogologo nke na-ebuli ogologo ahịrị iji kwekọọ akara niile dị na bọs yiri. Ọgụgụ 6 na -egosi ihe atụ nke okirikiri DDR3 nwere eriri mgbatị ogologo.

Metụtara na ụgbọ elu nke njuputa ala

Ngwa ụfọdụ nwere ihe ndị na-eme mkpọtụ, dị ka ikuku ikuku ma ọ bụ antenna, nwere ike ịchọ ntakịrị nchebe ọzọ. Ịmepụta wiwi na ụgbọ elu nwere oghere ala agbakwunyere nwere ike nyere aka belata njikọta nke ngwa wiring dị nso ma ọ bụ ụgbọ elu na akara ụgbọ elu nke na-adaba na nsọtụ bọọdụ ahụ.

Ọgụgụ 7 na-egosi ihe atụ nke modulu Bluetooth etinyere na nsọtụ efere ahụ, yana antenna ya (site na ihuenyo e biri ebi akara “ANT”) na mpụga ahịrị nwere oghere agbakwunyere na njikọ ala. Nke a na -enye aka ikewapụ antenna site na sekit na ụgbọ elu ndị ọzọ.

Enwere ike iji usoro ọzọ nke ịgagharị n’ime ala (na nke a, ụgbọ elu polygonal) iji kpuchido sekit bọọdụ site na akara ikuku ikuku na-apụ apụ. Ọgụgụ 8 na-egosi PCB na-enwe mmetụta mkpọtụ nwere ụgbọ elu agbakwunyere na oghere n’akụkụ akụkụ bọọdụ ahụ.

Omume kachasị mma maka wiwi PCB

Many factors determine the wiring characteristics of the PCB field, so be sure to follow best practices when wiring your next PCB, and you’ll find a balance between PCB fab cost, circuit density, and overall performance.