With the increasing speed of PCB ke kuapo hōʻailona, ​​pono i nā mea hoʻolālā PCB o kēia lā e hoʻomaopopo a kāohi i ka impedance o nā koina PCB. E like me nā manawa hoʻoili o ka hōʻailona pōkole a me nā helu uaki ʻoi aku o nā kaapuni uila o kēia manawa, ʻaʻole nā ​​pilina PCB e pili maʻalahi, akā nā laina hoʻoili.

Pehea e kaohi ai i ka impedance PCB

I ka hoʻomaʻamaʻa, pono ia e kaohi i ka impedance trace ke ʻoi aku ka wikiwiki o ka wikiwiki kikoʻī i 1ns a i ʻoi aku ka nui o ka pinepine analog ma 300Mhz. ʻO kekahi o nā palena kikoʻī o kahi PCB trace kona ʻano impedance (ka lakio o ka uila i kēia manawa ke hele ka nalu ma ka laina loli hoʻoliʻiliʻi). ʻO ka impedance ʻano o ka uea ma ka papa kaapuni i paʻi ʻia kahi helu nui o ka hoʻolālā papa kaapuni, keu hoʻi i ka hoʻolālā PCB o ke kaʻina alapine kiʻekiʻe, pono e noʻonoʻo inā kūlike ka impedance ʻano o ka uea me ka impedance ʻano e koi ʻia e ka hāmeʻa a hōʻailona paha. This involves two concepts: impedance control and impedance matching. This paper focuses on impedance control and lamination design.

Kaohi Impedance

Ka mālama ʻana ʻo EImpedance, e loaʻa i ka mea alakaʻi i ka papa kaapuni nā ʻano like o ka lawe ʻana o ka hōʻailona, ​​i mea e hoʻomaikaʻi ai i ka nui o ka lawe ʻana a pono e hoʻonui i kona alapine, inā ʻo ka laina ponoʻī ma muli o ka hoʻopaʻa ʻana, ka mānoanoa o ka paʻa, ka laula uea a me nā kumu ʻē aʻe, e kumu hoʻololi i ka waiwai impedance, ka distortion hōʻailona. No laila, ʻo ka waiwai impedance o ka mea alakaʻi ma ka papa kaapuni wikiwiki e pono e hoʻomalu ʻia i loko o kahi pae, i ʻike ʻia ʻo “impedance control”.

The impedance of a PCB trace will be determined by its inductive and capacitive inductance, resistance, and conductivity coefficient. ʻO nā kumu nui e hoʻopili ana i ka impedance o ka hoʻopili PCB: ka laulā o ka uea keleawe, ka mānoanoa o ka uea keleawe, ka hoʻomau dielectric o ka waena, ka mānoanoa o ka waena, ka mānoanoa o ka pale, ke ala o ka uea honua, nā uwea a puni nā pilina. , etc. Loaʻa ka impedance PCB mai 25 a 120 ohm.

I ka hana, kahi laina hoʻoili PCB i maʻa mau i kahi kuhi, hoʻokahi a ʻoi paha mau papa kuhikuhi, a me nā mea hoʻīpī. Nā meheu a me nā papa e hana i ka impedance kaohi. E hoʻonui pinepine ʻia ʻo PCBS, a hiki ke kūkulu ʻia ka impedance kaohi ma nā ʻano like ʻole. However, whatever method is used, the impedance value will be determined by its physical structure and the electrical properties of the insulating material:

Ka laula a me ka mānoanoa o ka hōʻailona hōʻailona

The height of the core or prefill material on either side of the trace

ʻO ka hoʻonohonoho ʻana o ka trace a me ka pā

Insulation constants of core and prefilled materials

Hele mai nā laina hoʻoili PCB i nā ʻano nui ʻelua: ʻO Mikroptrip a me Stripline.

Microstrip:

ʻO kahi laina microstrip kahi alakaʻi alakaʻi me kahi mokulele kūmole ma hoʻokahi ʻaoʻao, me ka luna a me nā ʻaoʻao i hōʻike ʻia i ka ea (a i ʻole i uhi ʻia), ma luna o ka papa o ka hoʻoneʻe mau o ka papa kaapuni Er, me ka lako mana a i ʻole ke kahua ma ke ʻano he kūmole. E like me ka mea i hōʻike ʻia ma lalo:

Nānā: Ma ka hana PCB maoli, ʻaʻahu ka mea hana papa i ka papa o ka PCB me kahi papa o ka aila ʻōmaʻomaʻo, no laila i ka helu impedance maoli, hoʻohana ʻia ke k modelkohu i hōʻike ʻia ma lalo nei no ka helu helu microstrip ʻili:

Laina:

ʻO kahi laina lipine kahi lipine o ka uea i hoʻonoho ʻia ma waena o ʻelua mau mokulele kūmole, e like me ka mea i hōʻike ʻia ma ke kiʻi ma lalo. Hiki ke ʻokoʻa nā dielectric Constant o ka dielectric i hōʻike ʻia e H1 a me H2.

The above two examples are only a typical demonstration of microstrip lines and ribbon lines. There are many kinds of specific microstrip lines and ribbon lines, such as coated microstrip lines, which are related to the specific laminated structure of PCB.

The equations used to calculate the characteristic impedances require complex mathematical calculations, usually using field solving methods, including boundary element analysis, so using the specialized impedance calculation software SI9000, all we need to do is control the parameters of the characteristic impedances:

Dielectric constant Er, wiring width W1, W2 (trapezoid), wiring thickness T and insulation layer thickness H.

W1, W2:

The calculated value must be within the red box. A pela aku.

Hoʻohana ʻia ʻo SI9000 e hoʻomaulia inā hoʻokō ʻia nā koi hoʻokele impedance:

E helu mua i ka mana impedance hopena hoʻokahi o ka laina ʻikepili DDR:

TOP layer: 0.5oz keleawe mānoanoa, 5MIL uea ākea, 3.8mil mamao mai ka mokulele kuhikuhi, dielectric mau i ka 4.2. Koho i ke k modelkohu, pani i n parameters palena, a koho Lossless Calculation, e like me ka mea i hōʻike ʻia i ke kiʻi.

CoaTIng ʻo ia hoʻi coaTIng, a inā ʻaʻohe coaTIng, e hoʻopihapiha i ka mānoanoa a me ka 0 i ka dielectric (dielectric tumau) (ea).

Kū ka Substrate i ka papa substrate, ʻo ia hoʻi, layer dielectric, e hoʻohana maʻamau ana i ka fr-4, ka mānoanoa i helu ʻia e ka impedance calculator software, dielectric tumau 4.2 (alapine ma lalo o 1GHz).

Click on Weight (oz) to set the thickness of the copper layer, which determines the thickness of the cable.

9. ʻO ka manaʻo prepreg / Core o ka papa hoʻoneʻe:

ʻO PP (Prepreg) kahi ʻano dielectric material, i haku ʻia me ke aniani puluniu a me ka epoxy resin. ʻO Core maoli kahi ʻano o ka PP medium, akā uhi ʻia kona mau ʻaoʻao ʻelua me ka pepa keleawe, ʻoiai ʻaʻole ʻo PP. Ke hana maʻamau ʻia nā papa multilayer, kāna a me PP, a hoʻohana ʻia ʻo PP e hoʻopaʻa ma waena o ke kumu a me ke kumu.

10. Nā mea e pono ai ka nānā ʻana i ka hoʻolālā lamination PCB

(1) Pilikia pilikia

Pono e hoʻohālikelike ka hoʻolālā papa o PCB, ʻo ia hoʻi, ka mānoanoa o ka papa waena a me ka papa keleawe o kēlā me kēia papa e like me ka symmetrical. Lawe i ʻeono mau papa no ka laʻana, e kūlike ka mānoanoa o ka top-GND a me ka medium-power me ka mānoanoa o ke keleawe, A ʻo GND-L2 a me L3-POWER medium e kūlike me ka mānoanoa o ke keleawe. ʻAʻole e warp kēia inā laminating.

(2) E hoʻopili pono ʻia ka papa hōʻailona me ka mokulele pili e pili ana (ʻo ia hoʻi, ka mānoanoa waena ma waena o ka papa hōʻailona a me ka pale uhi keleawe pili pono e liʻiliʻi loa); Pono e hoʻopili pono ʻia nā lole keleawe mana a me nā lole keleawe lepo.

(3) I ke kumu o ka wikiwiki loa, hiki ke hoʻohui ʻia i nā papa keu e hoʻokaʻawale i ka papa hōʻailona, ​​akā koi ʻia ʻaʻole e hoʻokaʻawale i nā papa mana he nui, i mea e hoʻonāukiuki ai ka walaʻau kūpono ʻole.

(4) Hōʻike ʻia ka mahele o nā papa hoʻolālā laminated maʻamau i ka papa aʻe:

(5) Nā kulekele laula o ka hoʻonohonoho papa:

Ma lalo o ka ʻāpana o ka ʻāpana (ka papa ʻelua) ka mokulele honua, kahi e hāʻawi ai i ka pale pale a ka mea a me ka mokulele kūmole no ka uea papa kiʻekiʻe;

Hoʻopili nā hōʻailona hōʻailona āpau i ka mokulele honua a hiki i ka hiki.

Hōʻalo i ka pili pololei ma waena o nā papa hōʻailona ʻelua a hiki i ka hiki;

Pono ka lako mana nui e pili kokoke i ka hiki;

Lawe ʻia ka symmetry o ka hanana laminate.

For the layer layout of the motherboard, it is difficult for the existing motherboard to control the parallel long-distance wiring, and the working frequency of the board level is above 50MHZ

(No nā kūlana ma lalo o 50MHZ, e ʻoluʻolu e nānā iā ia a hoʻomaha kūpono ia).

Component ʻili a me ka kuʻihao ʻili i piha mokulele mokulele (pale kaua);

ʻAʻohe pili pili pili pili like;

Hoʻopili nā hōʻailona hōʻailona āpau i ka mokulele honua a hiki i ka hiki.

Pili ka hōʻailona kī i ka hoʻokumu a ʻaʻole hele i ka ʻāpana hoʻokaʻawale.