Hauv kev siv ntau zaus xws li 5G hauv paus chaw nres tsheb, 77GHz millimeter yoj radar, kev sib txuas lus satellite, thiab lwm yam, Rogers + fr4 hybrid tau dhau los ua kev lag luam tus qauv kev daws teeb meem uas sib npaug RF kev ua haujlwm thiab kev tswj hwm tus nqi. Los ntawm kev siv Rogers tsuas yog nyob rau hauv cov teeb liab zaus zaus thiab fr4 hauv lwm txheej, cov khoom siv yuav raug txo los ntawm 30% -70%. Tab sis sib xyaw nias tsis yog ib qho teeb meem ntawm cov khoom sib dhos, thiab cov txheej txheem kev sib tw los ntawm qhov sib txawv ntawm lub cev ntawm ob cov ntaub ntawv ua rau nws yog "touchstone" rau kev ntsuas lub zog ntawm pcb siab.manufacturers.
1, Dab tsi yog qhov nyuaj ntawm cov txheej txheem sib xyaw ua ke? Plaub technological bottlenecks
1.1 CTE mismatch - lub hauv paus ua rau delamination thiab warping
Qhov sib txawv ntawm coefficient ntawm thermal expansion (CTE) yog qhov tseem ceeb tsis sib haum xeeb hauv cov txheej txheem sib xyaw ua ke, uas ncaj qha txiav txim siab lub siab txwv ntawm kev ntseeg siab ntawm cov phaj sib xyaw:
| Hom khoom | Z-axis CTE (ppm /℃C) | X/Y-axis CTE (ppm/degree C) | Tg (degree) |
|---|---|---|---|
| Txheem fr4 | 50~70 | 12~16 | 130~140 |
| High Tg fr4 | 25~30 | 12~16 | Ntau dua lossis sib npaug li 170 |
| Rogers RO4350B | 32 | 10~12 | >280 |
| Rogers RO4003C | 46 | 11~14 | >280 |
| Rogers RO4835 | 28 | 10~12 | >280 |
| PTFE chav kawm (RT / duroid 5880) | 200~300 | 50~100 | 327 |
Chain tsis ua hauj lwm tshwm sim los ntawm CTE mismatch:
Interlayer delamination: Thaum lub ncov kub ntawm reflow soldering yog 245-260℃C, qhov sib txawv ntawm Z-axis expansion ntawm ob cov ntaub ntawv tuaj yeem ncav cuag kaum tawm micrometers, thiab interfacial shear stress tuaj yeem ncav cuag 2-3MPa. Yog tias lub zog sib txuas tsis txaus, delamination tuaj yeem ua ncaj qha
Kev tawg ntawm lub qhov tooj liab: Thaum lub sij hawm thermal cycling, rov qab tensile compressive kev nyuaj siab yog concentrated nyob rau hauv lub qhov phab ntsa, thiab tooj liab qhov nrog ib tug tuab ntawm 20-25 μ m yog nquag mus rau microcracks nyob rau hauv nruab nrab, ua rau qhib circuits.
Warping deformation: Asymmetric stacking tuaj yeem sib txawv mus txog 1.2-2.5 mm / m, thiab warping ntawm 0.1mm tuab FR-4 tov nrog PTFE tuaj yeem tshaj 1.9cm, deb tshaj li 0.75% xav tau ntawm IPC-6012 tus qauv
Cov kauj ruam impedance: Thaum lub teeb liab kab hla ib qho nruab nrab, ib qho +7 Ω qhov siab tshaj plaws tau tsim tawm, ua rau muaj teeb meem cuam tshuam
Cov ntaub ntawv xeem tiag tiag: Tom qab thermal cycling ntawm -40℃C ~ 85℃C, qhov delamination tus nqi ntawm cov phaj sib xyaw tsis zoo tuaj yeem ncav cuag 12%, thiab cov teeb liab ruaj khov poob qis los ntawm 25%.
Qhov teeb meem ntawm nias kub tshwm sim los ntawm qhov sib txawv ntawm Tg 1.2
Qhov zoo tshaj plaws compression kub rau fr4 yog 170 ~ 185℃C, thiab nws yuav tsum tau tag nrho crosslinked thiab kho
Rogers RO4000 series muaj Tg ntawm kwv yees li 280℃C thiab qhov kev siv tau zoo, tab sis cov ntaub ntawv PTFE yog qhov ua rau me ntsis deformation ntawm qhov kub thiab txias.
Kev ntxhov siab: Kev kub ntau dhau ua rau Rogers deform thiab poob tswj cov kua nplaum ntws; Yog tias qhov kub thiab txias qis dhau lawm, daim ntawv fr4 semi cured yuav tsis kho kom txaus thiab cov interlayer adhesion yuav tsis txaus.
1.3 Dielectric qhov tsis sib xws - impedance discontinuity teeb meem
Rogers RO4350B: Dk≈3.48, Df≈ 0.0037@10GHz
Txheem FR-4: Dk ≈ 4.2 ~ 4.8, Df ≈ 0.018 ~ 0.025 @ 10GHz
Nyob rau hauv tib txoj kab dav, thaum lub teeb liab hla los ntawm Rogers mus rau thaj tsam fr4, lub impedance offset tuaj yeem ncav cuag ob peb ohms. Hla txheej hloov ntawm siab - cov kab teeb liab zaus tuaj yeem ua rau lub teeb liab cuam tshuam loj heev thiab cuam tshuam tsis zoo.
1.4 PTFE cov ntaub ntawv muaj qhov tsis tshua muaj zog saum npoo - qhov tsis muaj zog ntawm kev sib txuas
Lub zog saum npoo ntawm PTFE raws li Rogers cov ntaub ntawv tsuas yog 18-20 mN / m (fr4 yog li 40-50 mN / m), thiab lawv cov natural hydrophobicity thiab tshuaj inertness ua rau:
Tsis zoo adhesion rau tooj liab ntawv ci thiab semi cured ntawv
Thaum tsis qhib, lub zog ntawm lub ntsej muag ntawm lub ntsej muag yog qis dua li ntawm fr4 txheej
Nyob rau hauv thermal shock, nws yog feem ntau delamination, tawg, thiab tooj liab detachment nyob rau hauv pores
2, Rogers + fr4 yuav raug nias zoo li cas? Tag nrho cov txheej txheem technology daws
Kauj Ruam 1: Xaiv cov khoom siv - Narrowing CTE Gap los ntawm Qhov Chaw
Nyiam 'mixable' Rogers cov khoom:
Nyiam RO4000 series: RO4350B, RO4003C, RO4835 tshwj xeeb tsim los sib xyaw nrog fr4, nrog rau X / Y axis CTE ntawm 10-14 ppm /℃C ze rau FR-4's 12-16 ppm /℃C
Qhov zoo tshaj plaws tov rau ceramic filling: Z-axis CTE ntawm RO4835 yog 28 ppm /℃C, uas txo qhov sib txawv nrog siab Tg fr4 (25 ppm /℃C) mus rau hauv 10%, thiab txo qhov kev pheej hmoo ntawm thermal stress mismatch
PTFE cov ntaub ntawv yuav tsum tau ceev faj: Yog hais tias nws yog tsim nyog los siv PTFE substrates xws li RT / duroid 5880, RO4350B yuav tsum tau configured ntawm ob sab raws li ib tug kev hloov txheej txheej los ua ib tug CTE gradual gradient.
fr4 yuav tsum tau upgraded rau ib tug siab Tg khoom:
Siv qis CTE fr4 nrog Tg Ntau dua lossis sib npaug rau 170℃C, Z-axis CTE tuaj yeem ua kom zoo rau 25-30 ppm /℃C
Nws raug txwv tsis pub siv Tg zoo tib yam =130~ 140℃C FR-4 rau kev sib xyaw ua ke, vim tias qhov kev ntseeg ntawm thermal cycling tsis tuaj yeem lav.
Kauj ruam 2: Stacking Design - Symmetry yog Iron Law
Kev tswj hwm 100% daim iav symmetric stacking yog txoj hauv kev zoo tshaj plaws los tswj warping:
Cov khoom siv, thickness, tooj liab thickness, thiab PP qauv ntawm lub sab sauv thiab qis dielectric khaubncaws sab nraud povtseg yuav tsum tau kiag li symmetrical, nrog rau lub PCB nruab nrab txheej raws li axis ntawm symmetry
Lub siab - cov txheej txheej zaus yuav tsum tau muab sib xyaw ua ke ua khub, thiab nws raug txwv nruj kom tso ib txheej ntawm cov khoom siv ntau zaus ntawm ib sab
Hom 6-txheej sib xyaw ua ke siab qauv piv txwv:
TextL1: RO4350B (siab-frequency teeb liab txheej) L2: PP (RO4450F) L3: siab Tg fr4 (tsim) L4: siab Tg fr4 (lub hwj chim txheej) L5: siab Tg fr4 (tsim) L6: PP (RO4450F) L715B (RO4re3 txheej) Daim iav symmetry nrog L1
Hom 10 txheej txheej: L1 (RO4350B) / L2 (PP) / L3-L8 (FR-4) / L9 (PP) / L10 (RO4350B)
Cov txiaj ntsig kev xeem tiag tiag: Symmetrical stacking tuaj yeem txo qhov warpage tom qab thermal cycling los ntawm 1.2% mus rau hauv 0.5%.