Sida loo xakameeyo PCB caqabad la’aan?

Without impedance control, considerable signal reflection and distortion will be caused, resulting in design failure. Calaamadaha caadiga ah, sida baska PCI, baska PCI-E, USB, Ethernet, xusuusta DDR, signalada LVDS, iwm, dhammaantood waxay u baahan yihiin xakameyn is-xakamayn. Xakamaynta impedance ugu dambayntii waxay u baahan tahay in lagu xaqiijiyo iyada oo loo marayo naqshadda PCB, taas oo sidoo kale soo bandhigaysa shuruudo ka sarreeya tiknoolajiyadda guddiga PCB. Ka dib markii lala xiriiray warshadda PCB oo lagu daray adeegsiga softiweerka EDA, carqaladaynta fiilooyinka waxaa lagu xakameynayaa iyadoo la raacayo shuruudaha daacadnimada signalada.

Hababka fiilooyinka kala duwan ayaa loo xisaabin karaa si loo helo qiimaha isku -dheelitir la’aanta.

Microstrip lines

• Waxay ka kooban tahay xarig silig ah oo leh diyaaradda dhulka iyo korontada dhexda. Haddii joogteynta dielectric, ballaca xarriiqda, iyo masaafadeeda ka timaadda diyaaradda dhulka waa la xakamayn karaa, markaa jaan -goynta dabeecadeedda waa la xakamayn karaa, saxnimaduna waxay ku jiri doontaa ± 5%.

What is impedance control how to perform impedance control on PCB

Marin

Xarriiqda xariggu waa xadhig naxaas ah oo dhexda ku jira oo u dhexeeya laba diyaaradood oo hawsha wada. Haddii dhumucda iyo ballaca xarriiqda, joogteynta dielectric ee dhexdhexaadka ah, iyo masaafada u dhexeysa diyaaradaha dhulka ee labada lakab waa la xakamayn karaa, is -xakamaynta dabeecadda ee xarriiqdu waa la xakamayn karaa, saxnimaduna waxay ku jirtaa 10%.

What is impedance control how to perform impedance control on PCB

The structure of multi-layer board:

Si loo xakameeyo impedance PCB si fiican, waxaa lagama maarmaan ah in la fahmo qaab -dhismeedka PCB:

Sida caadiga ah waxa aan ugu yeerno guddiga multilayer wuxuu ka kooban yahay saxan asaasiga ah iyo xaashi adag oo la adkeeyay oo midba midka kale la dahaadhay. Looxa muhiimka ah waa dhumuc adag oo qaas ah, laba saxan oo naxaas ah oo roodhi ah, oo ah alaabta aasaasiga ah ee looxa daabacan. And the semi-cured piece constitutes the so-called infiltration layer, plays the role of bonding the core plate, although there is a certain initial thickness, but in the process of pressing its thickness will occur some changes.

Sida caadiga ah labada lakab ee korontada ku shaqeeya ee multilayer waa lakabyo qoyan, oo lakabyo bireed oo naxaas ah ayaa loo isticmaalaa bannaanka labadan lakab oo ah bireedka naxaasta dibadda ah. Faahfaahinta dhumucda asalka ah ee bireedka naxaasta ah ee dibadda ah iyo bireedka naxaasta gudaha ah guud ahaan 0.5oz, 1OZ, 2OZ (1OZ wuxuu ku saabsan yahay 35um ama 1.4mil), laakiin ka dib markii taxane daaweyn dusha ah, dhumucda kama dambaysta ah ee bireedka naxaasta dibadda ayaa guud ahaan kordhaysa 1OZ. Xarigga naxaasta ah ee gudaha ah waa daboolka naxaasta ah ee labada dhinac ee saxanka muhiimka ah. Dhumucda kama dambaysta ah wax yar bay kaga duwan tahay dhumucdii asalka ahayd, laakiin guud ahaan waxaa hoos u dhacay dhowr um oo ay sababtay xoqitaanku.

The outermost layer of the multilayer board is the welding resistance layer, which is what we often say “green oil”, of course, it can also be yellow or other colors. The thickness of the solder resistance layer is generally not easy to determine accurately. The area without copper foil on the surface is slightly thicker than the area with copper foil, but because of the lack of copper foil thickness, so the copper foil is still more prominent, when we touch the printed board surface with our fingers can feel.

Marka dhumuc gaar ah loox la daabaco la sameeyo, dhinaca kale, waxaa loo baahan yahay xulasho macquul ah oo ah xuduudaha maaddada, dhanka kale, dhumucda ugu dambaysa ee xaashida badhkeed la daaweeyey ayaa ka yaraan doonta dhumucda hore. Kuwa soo socdaa waa qaab-dhismeed 6-lakab oo dahaar ah:

What is impedance control how to perform impedance control on PCB

PCB parameters:

Different PCB plants have slight differences in PCB parameters. Through communication with circuit board plant technical support, we obtained some parameter data of the plant:

Dusha -bireed copper

There are three thicknesses of copper foil that can be used: 12um, 18um and 35um. Dhumucda ugu dambeysa ka dib dhammaystirka waxay ku saabsan tahay 44um, 50um iyo 67um.

Saxanka muhiimka ah: S1141A, heerka FR-4, laba taargood oo naxaas ah oo roodhi ah ayaa caadi ahaan la isticmaalaa. Tilmaamaha ikhtiyaarka ikhtiyaariga ah waxaa lagu go’aamin karaa marka lala xiriiro soo -saaraha.

Semi-cured tablet:

Tilmaamaha (dhumucda asalka ah) waa 7628 (0.185mm), 2116 (0.105mm), 1080 (0.075mm), 3313 (0.095mm). Dhumucda dhabta ah ka dib marka la riixo badiyaa waa qiyaastii 10-15um ka yar qiimihii asalka ahaa. Ugu badnaan 3 kiniin oo la-bogsiiyey ayaa loo isticmaali karaa isla lakabka faleebo, iyo dhumucda 3 kiniin oo la-bogsiiyey isku mid ma noqon karaan, ugu yaraan hal kiniin oo la bogsiiyey ayaa la isticmaali karaa, laakiin soo-saarayaasha qaarkood waa inay isticmaalaan ugu yaraan laba . Haddii dhumucda gabal-ka-bogsiintu aysan ku filnayn, bireedka naxaasta ah ee labada dhinac ee saxanka asaasiga ah waa la tirtiri karaa, ka dibna qaybta badh-la-bogsiiyey waxaa lagu xiri karaa labada dhinac, si lakabka dhex-dhumucdiisu ka sii weynaato la gaaray.

Lakabka alxanka Resistance:

Dhumucda lakabka iska caabinta alxanka ee bireedka naxaasku waa C2≈8-10um. Dhumucda lakabka iska -caabbinta dusha sare ee aan lahayn bireedka naxaasku waa C1, kaas oo ku kala duwan dhumucda naxaasta dushiisa. Marka dhumucda naxaasta dusheeda ay tahay 45um, C1≈13-15um, iyo marka dhumucda naxaasta dusheeda ay tahay 70um, C1≈17-18um.

Qaybta ka gudubta:

Waxaan u maleyneynaa in qeybta isgoyska ee silig ay tahay leydi, laakiin dhab ahaantii waa trapezoid. Qaadashada lakabka TOP tusaale ahaan, marka dhumucda bireedka naxaasku yahay 1OZ, geeska hoose ee trapezoid waa 1MIL oo ka gaaban geeska hoose. Tusaale ahaan, haddii ballaca xarriiqdu yahay 5MIL, markaa dhinacyada sare iyo hoose waxay qiyaastii yihiin 4MIL halka dhinacyada hoose iyo hoose ay qiyaastii yihiin 5MIL. Farqiga u dhexeeya cidhifyada sare iyo hoose wuxuu la xiriiraa dhumucda naxaasta. Jadwalka soo socdaa wuxuu muujinayaa xiriirka ka dhexeeya sare iyo hoose ee trapezoid oo ku jira xaalado kala duwan.

What is impedance control how to perform impedance control on PCB

Oggolaanshaha: Oggolaanshaha xaashiyaha la-bogsiiyay waxay la xiriirtaa dhumucda. Jadwalka soo socda wuxuu muujinayaa dhumucda iyo xaddidnaanta oggolaanshaha ee noocyada kala duwan ee xaashiyaha badhkood la bogsiiyey:

What is impedance control how to perform impedance control on PCB

Joogtada dielectric ee saxanka waxay la xiriirtaa maaddada cusbi ee la isticmaalo. Joogtada korontada ee saxanka FR4 waa 4.2 – 4.7, waxayna hoos u dhacdaa kororka soo noqnoqoshada.

Cilladda luminta Dielectric: agabyada korantada ee ku hoos jira ficilka beddelka korantada, sababtuna tahay kuleylka iyo isticmaalka tamarta waxaa loo yaqaan luminta korantada, badiyaa waxaa lagu muujiyaa qodobka luminta korantada Tan δ. Qiimaha caadiga ah ee S1141A waa 0.015.

Ballaca khadka ugu yar iyo kala -dheereynta xariiqda si loo hubiyo mashiinnada: 4mil/4mil.

Hordhaca aaladda xisaabinta impedance:

Markaan fahanno qaab -dhismeedka guddiga isku -dheelitirka badan isla markaana aan si fiican u baranno xuduudaha loo baahan yahay, waxaan ku xisaabin karnaa is -hortaagga barnaamijka EDA. Waxaad u adeegsan kartaa Allegro si aad tan u samayso, laakiin waxaan kugula talinayaa Polar SI9000, oo ah aalad wanaagsan oo lagu xisaabinayo is -beddellada dabeecadda oo ay hadda adeegsadaan warshado badan oo PCB ah.

Markaad xisaabineysid carqaladeynta astaamaha gudaha ee labada xariiqa kala duwanaanta iyo khadka tooska ah, waxaad ka heli doontaa kaliya farqi yar oo u dhexeeya Polar SI9000 iyo Allegro sababo la xiriira faahfaahinta qaarkood, sida qaabka qeybta isgoyska ee siligga. Si kastaba ha noqotee, haddii ay tahay in la xisaabiyo is -beddelka dabeecadda ee astaanta dusha, waxaan kuu soo jeedinayaa inaad doorato moodalka la daboolay halkii laga beddeli lahaa qaabka Surface, maxaa yeelay moodooyinka noocaas ah waxay tixgeliyaan jiritaanka lakabka iska -caabbinta alxanka, sidaa darteed natiijadu waxay noqon doontaa mid sax ah. Kuwa soo socdaa waa shaashadda qayb ahaan ah ee xarriiqda kala -duwanaanta dusha sare ee lagu xisaabiyey Polar SI9000 iyadoo la tixgelinayo lakabka iska -caabbinta iibiyaha:

What is impedance control how to perform impedance control on PCB

Maadaama dhumucda lakabka iska -caabbinta aan si fudud loo xakamayn, hab qiyaas ah ayaa sidoo kale loo adeegsan karaa, sida uu ku taliyay soo -saaraha guddiga: ka jar qiimo gaar ah xisaabinta moodeelka Surface. Waxaa lagugula talinayaa in carqaladeynta kaladuwanaantu ay tahay in laga jaray 8 ohms halka impedance-ka hal-dhamaadka ah laga jaray 2 ohms.

Shuruudaha PCB ee kala duwan ee fiilooyinka

(1) Go’aaminta habka taararka, xuduudaheeda iyo xisaabinta impedance. Waxaa jira laba nooc oo ah hababka kala duwanaanshaha ee marin -haadka: hab -kala -duwanaanshaha khadka microstrip ee dibedda iyo habka farqiga xariiqa gudaha. Impedance waxaa lagu xisaabin karaa software xisaabinta impedance la xiriira (sida POLAR-SI9000) ama qaaciddada xisaabinta impedance iyada oo loo marayo dejinta cabbir macquul ah.

(2) Sadarrada isometric ee isbarbar socda. Go’aami baaxadda xarriiqda iyo kala -dheereynta, oo si adag u raac ballaarinta xarriiqda iyo kala -dheereynta marka aad waddo. Kala -fogaanshaha u dhexeeya laba sadar waa inuu had iyo jeer ahaadaa mid aan is -beddelin, oo ah, inuu is -barbar socdo. There are two ways of parallelism: one is that the two lines walk in the same side-by-side layer, and the other is that the two lines walk in the over-under layer. Guud ahaan isku day inaad iska ilaaliso adeegsiga farqiga u dhexeeya lakabyada, taas oo ah sababta oo ah hawlgalka dhabta ah ee PCB ee geedi socodka, sababtuna tahay isku -dheelitirka isku -dhejinta ee dahaarka ah ayaa aad uga hooseeya inta la siiyay inta u dhexaysa saxitaanka qallajinta, iyo geedi socodka luminta korantada ee dahaarka ah, ma dammaanad qaadi karto kala -soocidda xarriiqda farqiga waxay la mid tahay dhumucda korantada isku -dhafka ah, waxay sababi doontaa farqiga u dhexeeya lakabyada kala -duwanaanshaha is -beddelka impedance. Waxaa lagugula talinayaa inaad isticmaasho farqiga u dhexeeya isla lakabka intii suurtogal ah.