US20030209799A1 - Copper plated PTH barrels and methods for fabricating - Google Patents
Copper plated PTH barrels and methods for fabricating Download PDFInfo
- Publication number
- US20030209799A1 US20030209799A1 US10/461,516 US46151603A US2003209799A1 US 20030209799 A1 US20030209799 A1 US 20030209799A1 US 46151603 A US46151603 A US 46151603A US 2003209799 A1 US2003209799 A1 US 2003209799A1
- Authority
- US
- United States
- Prior art keywords
- layer
- nickel
- wiring board
- metallization layer
- printed wiring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 52
- 239000010949 copper Substances 0.000 title claims abstract description 41
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 39
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 37
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 81
- 239000000758 substrate Substances 0.000 claims abstract description 45
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 38
- 239000003054 catalyst Substances 0.000 claims abstract description 20
- 239000003989 dielectric material Substances 0.000 claims abstract description 14
- 229910000570 Cupronickel Inorganic materials 0.000 claims abstract 2
- YOCUPQPZWBBYIX-UHFFFAOYSA-N copper nickel Chemical compound [Ni].[Cu] YOCUPQPZWBBYIX-UHFFFAOYSA-N 0.000 claims abstract 2
- 238000001465 metallisation Methods 0.000 claims description 62
- 238000007747 plating Methods 0.000 claims description 27
- 238000007772 electroless plating Methods 0.000 claims description 22
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 18
- 229920002120 photoresistant polymer Polymers 0.000 claims description 18
- 238000000151 deposition Methods 0.000 claims description 16
- 230000002093 peripheral effect Effects 0.000 claims description 14
- 230000003197 catalytic effect Effects 0.000 claims description 10
- 229910052763 palladium Inorganic materials 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 6
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 239000001301 oxygen Substances 0.000 claims description 6
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 claims description 5
- 239000003822 epoxy resin Substances 0.000 claims description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 4
- 229920000647 polyepoxide Polymers 0.000 claims description 4
- 238000012545 processing Methods 0.000 claims description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052737 gold Inorganic materials 0.000 claims description 2
- 239000010931 gold Substances 0.000 claims description 2
- 230000005484 gravity Effects 0.000 claims description 2
- 229910052697 platinum Inorganic materials 0.000 claims description 2
- 229910052723 transition metal Inorganic materials 0.000 claims description 2
- 150000003624 transition metals Chemical class 0.000 claims description 2
- 239000000725 suspension Substances 0.000 claims 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims 1
- 229910017052 cobalt Inorganic materials 0.000 claims 1
- 239000010941 cobalt Substances 0.000 claims 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims 1
- 229910052742 iron Inorganic materials 0.000 claims 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims 1
- 125000002524 organometallic group Chemical group 0.000 claims 1
- 238000000059 patterning Methods 0.000 claims 1
- 230000001681 protective effect Effects 0.000 claims 1
- 229910052709 silver Inorganic materials 0.000 claims 1
- 239000004332 silver Substances 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 239000004065 semiconductor Substances 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 90
- 239000002585 base Substances 0.000 description 20
- 239000000463 material Substances 0.000 description 18
- 239000000203 mixture Substances 0.000 description 14
- 229910052751 metal Inorganic materials 0.000 description 13
- 239000002184 metal Substances 0.000 description 13
- 230000008569 process Effects 0.000 description 13
- 239000000243 solution Substances 0.000 description 12
- 229920001577 copolymer Polymers 0.000 description 11
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 9
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 8
- 239000004593 Epoxy Substances 0.000 description 8
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 8
- 239000008139 complexing agent Substances 0.000 description 8
- 239000003638 chemical reducing agent Substances 0.000 description 7
- 229920000642 polymer Polymers 0.000 description 6
- -1 polytetrafluoroethylene Polymers 0.000 description 6
- NXLOLUFNDSBYTP-UHFFFAOYSA-N retene Chemical compound C1=CC=C2C3=CC=C(C(C)C)C=C3C=CC2=C1C NXLOLUFNDSBYTP-UHFFFAOYSA-N 0.000 description 6
- 239000004020 conductor Substances 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 5
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 4
- 239000000654 additive Substances 0.000 description 4
- 229940106691 bisphenol a Drugs 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 239000004094 surface-active agent Substances 0.000 description 4
- WVDDGKGOMKODPV-UHFFFAOYSA-N Benzyl alcohol Chemical compound OCC1=CC=CC=C1 WVDDGKGOMKODPV-UHFFFAOYSA-N 0.000 description 3
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- UORVGPXVDQYIDP-UHFFFAOYSA-N borane Chemical class B UORVGPXVDQYIDP-UHFFFAOYSA-N 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 238000005553 drilling Methods 0.000 description 3
- 229960001484 edetic acid Drugs 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- PIBWKRNGBLPSSY-UHFFFAOYSA-L palladium(II) chloride Chemical compound Cl[Pd]Cl PIBWKRNGBLPSSY-UHFFFAOYSA-L 0.000 description 3
- 229910052708 sodium Inorganic materials 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- LMVLMHGTZULBRX-UHFFFAOYSA-N 2-[2,2,2-tris(2-hydroxyphenyl)ethyl]phenol Chemical compound OC1=CC=CC=C1CC(C=1C(=CC=CC=1)O)(C=1C(=CC=CC=1)O)C1=CC=CC=C1O LMVLMHGTZULBRX-UHFFFAOYSA-N 0.000 description 2
- LXBGSDVWAMZHDD-UHFFFAOYSA-N 2-methyl-1h-imidazole Chemical compound CC1=NC=CN1 LXBGSDVWAMZHDD-UHFFFAOYSA-N 0.000 description 2
- RGHNJXZEOKUKBD-SQOUGZDYSA-N D-gluconic acid Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C(O)=O RGHNJXZEOKUKBD-SQOUGZDYSA-N 0.000 description 2
- 229910002666 PdCl2 Inorganic materials 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 239000003929 acidic solution Substances 0.000 description 2
- 230000001464 adherent effect Effects 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 229910000085 borane Inorganic materials 0.000 description 2
- 125000002091 cationic group Chemical group 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- GYZLOYUZLJXAJU-UHFFFAOYSA-N diglycidyl ether Chemical class C1OC1COCC1CO1 GYZLOYUZLJXAJU-UHFFFAOYSA-N 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 2
- 238000004080 punching Methods 0.000 description 2
- 125000001453 quaternary ammonium group Chemical group 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- GHMLBKRAJCXXBS-UHFFFAOYSA-N resorcinol Chemical compound OC1=CC=CC(O)=C1 GHMLBKRAJCXXBS-UHFFFAOYSA-N 0.000 description 2
- 238000010561 standard procedure Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229920001169 thermoplastic Polymers 0.000 description 2
- 229920001187 thermosetting polymer Polymers 0.000 description 2
- 239000004416 thermosoftening plastic Substances 0.000 description 2
- TXUICONDJPYNPY-UHFFFAOYSA-N (1,10,13-trimethyl-3-oxo-4,5,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthren-17-yl) heptanoate Chemical compound C1CC2CC(=O)C=C(C)C2(C)C2C1C1CCC(OC(=O)CCCCCC)C1(C)CC2 TXUICONDJPYNPY-UHFFFAOYSA-N 0.000 description 1
- BGJSXRVXTHVRSN-UHFFFAOYSA-N 1,3,5-trioxane Chemical compound C1OCOCO1 BGJSXRVXTHVRSN-UHFFFAOYSA-N 0.000 description 1
- QTWJRLJHJPIABL-UHFFFAOYSA-N 2-methylphenol;3-methylphenol;4-methylphenol Chemical compound CC1=CC=C(O)C=C1.CC1=CC=CC(O)=C1.CC1=CC=CC=C1O QTWJRLJHJPIABL-UHFFFAOYSA-N 0.000 description 1
- VEORPZCZECFIRK-UHFFFAOYSA-N 3,3',5,5'-tetrabromobisphenol A Chemical compound C=1C(Br)=C(O)C(Br)=CC=1C(C)(C)C1=CC(Br)=C(O)C(Br)=C1 VEORPZCZECFIRK-UHFFFAOYSA-N 0.000 description 1
- BDDLHHRCDSJVKV-UHFFFAOYSA-N 7028-40-2 Chemical compound CC(O)=O.CC(O)=O.CC(O)=O.CC(O)=O BDDLHHRCDSJVKV-UHFFFAOYSA-N 0.000 description 1
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 description 1
- OCUCCJIRFHNWBP-IYEMJOQQSA-L Copper gluconate Chemical class [Cu+2].OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C([O-])=O.OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C([O-])=O OCUCCJIRFHNWBP-IYEMJOQQSA-L 0.000 description 1
- RGHNJXZEOKUKBD-UHFFFAOYSA-N D-gluconic acid Natural products OCC(O)C(O)C(O)C(O)C(O)=O RGHNJXZEOKUKBD-UHFFFAOYSA-N 0.000 description 1
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 1
- 229920000459 Nitrile rubber Polymers 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 229930040373 Paraformaldehyde Natural products 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 229910021626 Tin(II) chloride Inorganic materials 0.000 description 1
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 1
- 229920000122 acrylonitrile butadiene styrene Polymers 0.000 description 1
- 239000012190 activator Substances 0.000 description 1
- 239000012790 adhesive layer Substances 0.000 description 1
- 150000001447 alkali salts Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- LHIJANUOQQMGNT-UHFFFAOYSA-N aminoethylethanolamine Chemical compound NCCNCCO LHIJANUOQQMGNT-UHFFFAOYSA-N 0.000 description 1
- ICAIHGOJRDCMHE-UHFFFAOYSA-O ammonium cyanide Chemical class [NH4+].N#[C-] ICAIHGOJRDCMHE-UHFFFAOYSA-O 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 125000002648 azanetriyl group Chemical class *N(*)* 0.000 description 1
- 150000007514 bases Chemical class 0.000 description 1
- 235000019445 benzyl alcohol Nutrition 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- YJROYUJAFGZMJA-UHFFFAOYSA-N boron;morpholine Chemical compound [B].C1COCCN1 YJROYUJAFGZMJA-UHFFFAOYSA-N 0.000 description 1
- ZTQYEZDTWTZXPF-UHFFFAOYSA-N boron;propan-2-amine Chemical compound [B].CC(C)N ZTQYEZDTWTZXPF-UHFFFAOYSA-N 0.000 description 1
- 229920003118 cationic copolymer Polymers 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- KXZJHVJKXJLBKO-UHFFFAOYSA-N chembl1408157 Chemical compound N=1C2=CC=CC=C2C(C(=O)O)=CC=1C1=CC=C(O)C=C1 KXZJHVJKXJLBKO-UHFFFAOYSA-N 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 229910000366 copper(II) sulfate Inorganic materials 0.000 description 1
- 229930003836 cresol Natural products 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- QGBSISYHAICWAH-UHFFFAOYSA-N dicyandiamide Chemical compound NC(N)=NC#N QGBSISYHAICWAH-UHFFFAOYSA-N 0.000 description 1
- 238000010981 drying operation Methods 0.000 description 1
- 125000003700 epoxy group Chemical group 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000011152 fibreglass Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000000174 gluconic acid Substances 0.000 description 1
- 235000012208 gluconic acid Nutrition 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 210000003127 knee Anatomy 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 238000000608 laser ablation Methods 0.000 description 1
- IHBKAGRPNRKYAO-UHFFFAOYSA-M methyl sulfate;trimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]azanium Chemical compound COS([O-])(=O)=O.CC(=C)C(=O)OCC[N+](C)(C)C IHBKAGRPNRKYAO-UHFFFAOYSA-M 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229910001453 nickel ion Inorganic materials 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 229920003986 novolac Polymers 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 239000003002 pH adjusting agent Substances 0.000 description 1
- 150000002940 palladium Chemical class 0.000 description 1
- 229920002866 paraformaldehyde Polymers 0.000 description 1
- WVDDGKGOMKODPV-ZQBYOMGUSA-N phenyl(114C)methanol Chemical compound O[14CH2]C1=CC=CC=C1 WVDDGKGOMKODPV-ZQBYOMGUSA-N 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- ACVYVLVWPXVTIT-UHFFFAOYSA-M phosphinate Chemical compound [O-][PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-M 0.000 description 1
- 125000005496 phosphonium group Chemical group 0.000 description 1
- 229920002492 poly(sulfone) Polymers 0.000 description 1
- 229920002401 polyacrylamide Polymers 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- LJCNRYVRMXRIQR-OLXYHTOASA-L potassium sodium L-tartrate Chemical class [Na+].[K+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O LJCNRYVRMXRIQR-OLXYHTOASA-L 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 239000012744 reinforcing agent Substances 0.000 description 1
- 230000001235 sensitizing effect Effects 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 235000011006 sodium potassium tartrate Nutrition 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000001119 stannous chloride Substances 0.000 description 1
- 235000011150 stannous chloride Nutrition 0.000 description 1
- 150000003512 tertiary amines Chemical class 0.000 description 1
- 125000005207 tetraalkylammonium group Chemical group 0.000 description 1
- 238000005382 thermal cycling Methods 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 1
- 229910001887 tin oxide Inorganic materials 0.000 description 1
- FWPIDFUJEMBDLS-UHFFFAOYSA-L tin(II) chloride dihydrate Chemical compound O.O.Cl[Sn]Cl FWPIDFUJEMBDLS-UHFFFAOYSA-L 0.000 description 1
- 229960004418 trolamine Drugs 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229920003169 water-soluble polymer Polymers 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
- H01L23/498—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers
- H01L23/49827—Via connections through the substrates, e.g. pins going through the substrate, coaxial cables
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
- H01L21/4814—Conductive parts
- H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
- H01L21/486—Via connections through the substrate with or without pins
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
- H05K3/42—Plated through-holes or plated via connections
- H05K3/425—Plated through-holes or plated via connections characterised by the sequence of steps for plating the through-holes or via connections in relation to the conductive pattern
- H05K3/427—Plated through-holes or plated via connections characterised by the sequence of steps for plating the through-holes or via connections in relation to the conductive pattern initial plating of through-holes in metal-clad substrates
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/03—Conductive materials
- H05K2201/0332—Structure of the conductor
- H05K2201/0335—Layered conductors or foils
- H05K2201/0344—Electroless sublayer, e.g. Ni, Co, Cd or Ag; Transferred electroless sublayer
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/14—Related to the order of processing steps
- H05K2203/1407—Applying catalyst before applying plating resist
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/108—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern by semi-additive methods; masks therefor
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
- H05K3/42—Plated through-holes or plated via connections
- H05K3/422—Plated through-holes or plated via connections characterised by electroless plating method; pretreatment therefor
Definitions
- the present invention relates to circuitized printed wiring board structures and especially to via barrels having enhanced copper adhesion.
- the enhanced adhesiveness of the copper plating provides improved performance in high temperature assembly operations.
- the present invention also provides a method for fabricating via barrels plated with highly adherent copper.
- the board In the manufacture of printed circuit boards, sometimes known as printed wiring boards, it is now commonplace to produce printed circuitry on both sides of a planar rigid or flexible insulating substrate. Of increased importance is the manufacture of multilayer printed circuits.
- the board In these products, the board consists of parallel, planar, alternating innerlayers of insulating substrate material and conductive metal. The exposed outer sides of the laminated structure are provided with circuit patterns as with double-sided boards, and the metal innerlayers may themselves contain circuit patterns.
- via holes are drilled or punched into or through the board structure at desired locations. Drilling or punching provides newly-exposed surfaces including via barrel surfaces and via peripheral entry surfaces.
- the dielectric substrate comprising a top surface, a bottom surface, and at least one exposed via hole surface, consisting partly or entirely of insulating material, is then metallized, generally by utilization of electroless metal depositing techniques.
- a dielectric sheet material is employed as the substrate.
- the substrate typically is an organic material, such as fiberglass-reinforced epoxy resin (FR4), polytetrafluoroethylene, etc. Since the dielectric substrate is nonconductive, in order to plate on the substrate, the substrate must be seeded or catalyzed prior to the deposition of metal onto the substrate.
- the electroless plating of copper onto a substrate is well-known in the art. For instance, an electroless or autocatalytic copper plating bath usually contains a cupric salt, a reducing agent for the cupric salt, a chelating or complexing agent, and a pH adjustor.
- a suitable catalyst is deposited onto the surface prior to contact with the plating bath.
- stannous chloride sensitizing solution and a palladium chloride activator to form a layer of metallic palladium particles.
- Copper is not highly adherent to the materials typically used as the dielectric substrate.
- the deposited copper is generally anchored to the exposed inner copper layers more than the dielectric.
- the copper “barrel” has a tendency to crack or delaminate, causing open circuits. Therefore a requirement exists for means to increase the bonding strength of the copper to the substrate.
- the present invention provides the desired increased durability of via barrels without the requirement for many of the additional processing steps and materials used in prior art solutions.
- Takahashi et al. U.S. Pat. No. 5,309,632
- Their method also plates nickel over the entire board surface and then strip the nickel in excess of the circuitization.
- the present invention provides via barrels exhibiting high copper to substrate adhesion.
- the present invention makes possible via barrels that survive the thermal stresses of high temperature assembly and have a longer thermal cycle life than bare copper barrels.
- the present invention provides via barrels which comprise: a wiring board of dielectric material wherein a plurality of via are defined; a catalyst seed layer located on the inner surface of the via within the dielectric material; a layer of nickel deposited on top of the catalyst seed layer; and a layer of copper plating in the openings and over the layer of nickel.
- the present invention also relates to fabricating the above disclosed printed circuit board.
- the method comprises: providing a board having a top surface and a bottom surface and comprised of one or more layers of dielectric material and optionally one or more inner conductive layers which are optionally personalized by provision of a pattern such as a circuit pattern; depositing a catalyst seed layer on the layer of dielectric material; depositing a layer of nickel on top of the catalyst seed layer; and depositing a layer of copper plating over the layer of nickel.
- Metallization of the dielectric substrate comprises providing a first metallization layer termed a catalytic seed layer and is typically palladium and tin; providing a second metallization layer wherein the layer is chosen from the group VIII and Group IB transition metals and is typically nickel; and providing a third metallization layer, typically copper.
- the catalytic seed layer is thus termed and the nickel and copper layers are respectively termed the “first metallization” and the “second metallization.”
- FIG. 1 is a schematic cross-section of base member
- FIG. 2 is a schematic transverse section of base member following formation of through hole
- FIG. 3 is a schematic cross-section of base member after contact with catalytic composition
- FIG. 4 is a schematic cross-section of base member after application of photoresist
- FIG. 5 is a schematic cross-section of base member after second metallization layer.
- FIG. 6 is a schematic cross-section of base member after third metallization layer.
- Base member 13 includes first and second conductive layers 1 and 3 , which sandwich there between, first and second dielectric layers 2 and 4 and conductive plane 5 .
- each of the two conductive layers is comprised of copper or a well-known conductive material, each having a thickness from about 0.25 mils (0.0025 inches) to about 1.5 mils with the thickness of each preferably being about 0.25 mils.
- each of the two dielectric layers is comprised of fiberglass reinforced epoxy resin (FR4).
- a typical FR-4 epoxy composition contains 70-90 parts of brominated polyglycidyl ether of bisphenol-A and 10-30 parts of tetrakis(hydroxyphenyl)ethane tetraglycidyl ether cured with 3 to 4 parts of dicyandiamide, and 0.2 to 0.4 parts of a tertiary amine, all parts being parts by weight per 100 parts of resin solids.
- Another typical FR-4 epoxy composition contains: a) about 25 to about 30 parts by weight of a tetrabrominated diglycidyl ether of bisphenol-A having an epoxy equivalent weight of about 350 to about 450; b) about 10 to about 15 parts by weight of a tetrabrominated diglycidyl ether of bisphenol-A having an epoxy equivalent weight of about 600 to about 750; and c) about 55 to about 65 parts by weight of at least one epoxidized non-linear novolak, having at least terminal epoxy groups, along with suitable curing and/or hardening agents.
- Another typical FR-4 epoxy composition contains about 70 to about 90 parts of brominated polyglycidyl ether of bisphenol-A, and 10 to 30 parts of tetrakis (hydroxyphenyl) ethane tetraglycidyl ether cured with 0.8 to 1 part of 2-methyl imidazole.
- Still another FR-4 epoxy composition employs tetrabromo bisphenol-A as the curing agent, along with 2-methyl imidazole as the catalyst.
- thermosetting polymeric materials include epoxy, phenolic based materials, and polyamides.
- the dielectric materials may be molded articles of the polymers containing fillers and/or reinforcing agents, such as glass-filled epoxy or phenolic based materials. Examples of some phenolic type materials include copolymers of phenol, resorcinol and cresol.
- thermoplastic polymeric materials examples include polyolefins, such as polypropylene, polysulfones, polycarbonates, nitrile rubbers, ABS polymers and fluorinated polymeric materials such as polytetrafluoroethylene.
- each dielectric layer possesses a thickness of from about 2 mils to about 20 mils. Thicknesses less than about 2 mils for this particular material may be undesirable because the resulting structure may be flimsy and difficult to handle during subsequent manufacturing processes. Thicknesses greater than about 20 mils may be undesirable because such thick dielectric layers, in addition to requiring relatively large conductor line widths and thicknesses, also may prevent optimum package electrical performance.
- conductive plane 5 Sandwiched between dielectric layers 2 and 4 is conductive plane 5 , preferably of copper or other well-known conductive material and possessing a thickness of preferably within the range of about 0.125 mils to about 2.5 mils.
- the thicknesses for plane 5 of less than about 0.125 mils may prove undesirable should the resulting structure by subjected to relatively high temperatures. Additionally, thicknesses greater than about 2.5 mils may prove undesirable because of the additional time necessary to form such layers using conventional plating techniques and associated difficulties with line width control.
- the resulting structure shown in FIG. 1 thus preferably possesses a thickness within the range of about 4.7 mils to about 400 mils.
- the preferred thickness is governed by the desired number of signal planes.
- Conductive layers 1 and 3 and dielectric layers 2 and 4 are bonded to the conductive plane 5 using a lamination process, such a process known in the art and further description is not believed necessary.
- Base member 13 is thus shown to include at least two surfaces, a first surface 6 , and a second surface 7 .
- base member 13 Although two conductive layers and two dielectric layers are shown for base member 13 , it is understood that the invention is not limited thereto. Specifically, it is only necessary to provide one such conductive layer and one such dielectric layer while still attaining the advantageous results taught herein. At least two layers of each are used when it is desired to incorporate an internal conductive plane (e.g., power, ground or signal) as part of the final structure. Understandably, several dielectric layers and corresponding internal conductive planes may be utilized, depending on operational requirements for the finished product.
- an internal conductive plane e.g., power, ground or signal
- opening 8 having an internal wall surface or via barrel surface 9 and having a via peripheral entry surface or knee 9 A is formed substantially through base member 13 .
- Opening 8 which may be any type of via, may be formed by mechanical drilling although other hole forming techniques such as punching and laser drilling can be used.
- the minimum diameter of opening 8 is governed by the depth of the hole such that an approximately unitary aspect ratio (hole diameter/depth) is achieved.
- the upper limit of hole diameter is a function of the purpose of the hole.
- first-metallization layer 10 on the surfaces 6 and 7 of base member 13 , and on internal wall 9 of opening 8 to act as a catalyst for future metallization layers.
- FIG. 3 shows base member 13 after contact with a composition containing a catalytic composition capable of initiating an electroless plating process providing a catalyst seed layer 10 .
- the catalyst seed layer 10 is alternatively referred to as the first metallization layer.
- the compositions contain a metal that can directly provide the catalytic sites, or serve as a precursor which leads to the catalytic sites.
- the metal present may be in the elemental form, an alloy, or compound, or mixtures thereof.
- the preferred metal catalysts are precious metals, such as gold, palladium, and platinum.
- a typical palladium composition contains about 1.2 to about 2.5 grams per liter of a palladium salt, which is preferably PdCl 2 , about 80 to about 150 grams per liter of a stannous salt, which is preferably SnCl 2 .2H 2 O, and about 100 to about 150 milliliters per liter of an acid which is preferably HCl.
- a palladium salt which is preferably PdCl 2
- a stannous salt which is preferably SnCl 2 .2H 2 O
- HCl is provided in the form of a 37% HCl solution
- about 280 to about 360 milliliters of the HCl solution is preferably employed.
- the most preferred composition contains about 1.5 grams per liter of PdCl 2 and about 280 milliliters per liter of 37% HCl.
- the composition is usually maintained at a temperature of about 65 ⁇ 10° F.
- the substrate can be treated with an acid or alkaline accelerator such as a 2% NaOH solution to remove excess tin which is typically deposited along with the Pd catalyst.
- an acid or alkaline accelerator such as a 2% NaOH solution to remove excess tin which is typically deposited along with the Pd catalyst. This step usually takes about 1 to about 5 minutes and, more typically, about 1 to about 2 minutes.
- the substrates can then be dried, such as by being vacuum dried in an oven for 30 minutes at a temperature of about 100° C. In the drying operation, all the water is driven off irreversibly from the colloidal particles, leaving a shell of oxygen in the form of insoluble tin oxide.
- the dielectric layers 2 and 4 can be treated with an acidic solution containing a multifunctional ionic copolymer containing at least two available cationic functional moieties.
- the preferred ionic moieties are quaternary phosphonium and quaternary ammonium groups.
- Copolymers containing at least two cationic moieties such as, for example, copolymers of polyacrylamide forming the inert backbone and functionally active tetraalkylammonium compounds, are commercially available and need not be described herein in detail.
- Multifunctional cationic copolymers of that type are Reten 210 and Reten 220, available from HERCULES, description of which can be found in “Water-Soluble Polymers”, Bulletin VC-482A, HERCULES, Inc., Wilmington, Del., 1989, disclosure of which is incorporated herein by reference.
- Reten 210 is in powder form and is a copolymer of acrylamide and beta-methacryloxyethyltrimethylammonium methyl sulfate, of which a 1% solution has a Brookfield viscosity of 600-1000 cps.
- Reten 220 is also in powder form and consists of the same monomers as Reten 210, but its 1% solution has a Brookfield viscosity of 800-1200 cps.
- the molecular weights of the Reten polymers are usually relatively high and vary from about 50,000 to about 1,000,000 or more.
- the quaternary ammonium groups provide the number of positive charges of the polymer.
- the ionic copolymer is employed as a dilute acidic solution of about 0.01% to about 1% by weight, and preferably about 0.05% to about 0.5% by weight of the copolymer.
- the acid contained in the solution is preferably H 2 SO 4 , and the pH value of the solution is between 0 and about 3.
- the use of a low pH value is preferred to obtain a relatively low viscosity of the copolymer solution to facilitate application of the polymer.
- the treatment with the ionic copolymer is generally about 1 minute to about 10 minutes, and preferably about 1 minute to about 2 minutes, and takes place at about room temperature.
- the multifunctional copolymer having a very good adhesion to the substrate surface, provides the surface with a charge opposite from that associated with the seed particles 10 applied to the substrate. This difference in polarity provides for electrostatic attraction of the seed particles.
- the substrate is rinsed to remove any excess polymer not adhering to the substrate surface.
- a layer 31 of photoimaging (photoresist) material is then applied to the surfaces of member 13 over the first metallization layer.
- the layer of photoresist possessed a thickness of from about 0.3 mils to about 2.0 mils.
- a preferred material is a positive-acting photoresist, various examples being known in the art, including T168 photoresist available from the E. I. du Pont de Nemours Corporation under this trade designation.
- T168 photoresist available from the E. I. du Pont de Nemours Corporation under this trade designation.
- a positive-acting photoresists when applied and exposed through a suitable photomask, undergo a physical and chemical change in the exposed areas that render these areas insoluble to the subsequent developing solution which is to be applied thereto.
- the resist-coated base member 13 is immersed in developing solution (e.g., benzyl alcohol or propylene carbonate), which allows the unexposed areas to be removed without excessive impact on the hardened, exposed area. Baking or other processes may be used to further harden the remaining, exposed portions, if desired. With positive-acting photoresists, the portions developed away form the openings to the catalyzed laminated surface for subsequent plating
- developing solution e.g., benzyl alcohol or propylene carbonate
- base member 13 is shown following the above exposure and removal (developing) operations. As such, only portions of photoresist layer 31 remain. These portions are represented by the numeral 11 . It is understood that the removed portions of the photoresist in turn result in openings 35 which, in turn, expose preselected areas on the respective surfaces on which circuitization is to eventually occur. Thus a predetermined pattern on both surfaces is provided. Furthermore, it is understood that the photomask is designed such that the internal wall 9 of through holes 8 are not exposed.
- a second metallization layer 12 is deposited into the photoresist openings formed on base member 13 and in through hole 8 .
- the second metallization conductive layer 12 comprises nickel.
- the thickness of this second metallization conductive layer may be from about 0.1 mils to about 0.15 mils preferably about 0.12 mils to about 0.13 mils.
- the nickel is deposited on the seed layer by immersing into an electroless nickel plating process as known in the industry. Plating chemistries for electroless nickel plating are well known in the industry and need not be described herein in any detail.
- Typical methods for depositing nickel on the surface or surfaces of a substrate involve immersing the substrate in an aqueous solution comprising as ingredients a source of nickel ions, a soluble reducing agent for the nickel, a metal complexing agent and pH adjusting agents under conditions effective to bring about electroless deposition of nickel on the surface or surfaces by means of chemical reduction.
- the nickel plating be carried out after the development of the layer of photoimageable material since it eliminates the possibility of electrical leakage between lines. If plated before the layer of photoimageable material, the presence of nickel beneath the layer of photoimageable material could result in electrical leakage between lines, especially when spaced relatively close to each other. In addition, the nickel bath is generally more active than a copper plating bath. Accordingly, circuitization yields are higher because the line will have fewer defects.
- the second metallization layer is deposited by conventional plating methods for electroless plating. These processes typically have their own in-line seeding means because typically it is desired to plate nickel only on another metal surface. Crucial to the present invention is that the typical precleaning/preconditioning steps normally associated with this electroless nickel process are not performed. These processes remove portions of the first metallization (seed) layer. The present invention achieves the plating of nickel directly on the laminate surface. Use of precleaning or preconditioning steps removes portions of the seed particles thus causing skip plating on the laminate. Where the metal adheres to only portions of the inner surface of the hole, the adhesion is poor resulting is shortened mean time between failure.
- a third metallization layer 14 is deposited on the second metallization layer 12 .
- This metallization layer is typically plated to the same height as the top of the photoresist, although not always. Generally, the photoresist thickness is matched to the final desired conductor thickness. This aids post plating processing, if needed, for planarizing to remove plated nodules or extraneous plating above the desired conductor height should it occur.
- application of the third metallization layer follows substantially immediately after application of the second metallization layer.
- nickel comprising the second metallization layer provides for enhanced adhesion of the copper to the substrate.
- Copper 14 is plated on the inner surfaces of the holes over the nickel layer 12 from an electroless plating bath to provide the desired PTH barrel thickness. Examples of suitable electroless copper plating baths can be found in U.S. Pat. Nos. 5,509,557, 4,707,377 and 4,904,506, disclosures of which are incorporated herein by reference.
- the copper electroless plating bath employed is generally an aqueous composition, which contains a source of cupric ion, a complexing agent for the cupric ion, and a pH adjustor, in addition to the cyanide ion source and oxygen.
- the plating bath also preferably includes a surface-active agent.
- the cupric ion source generally used is a cupric sulfate or a cupric salt of the complexing agent to be employed.
- the cupric ion source in the electroless plating bath is typically employed in amounts of about 9 to about 14, and more typically about 10 to about 12 grams per liter, calculated as CuSo 4 .5H 2 O.
- the most common reducing agent employed is formaldehyde.
- examples of some other reducing agents include formaldehyde precursors or formaldehyde homopolymers, such as paraformaldehyde, trioxane, and gloxal; borohydrides such as alkali metal borohydrides (sodium and potassium borohydrides) and substituted borohydrides such as sodium trimethoxy borohydride; boranes such as amine borane (isopropyl amine borane and morpholine borane); and hypophosphite reducing agents.
- the reducing agent is generally present in amounts from about 1 to about 4 milliliters per liter, and more typically from about 2 to about 2.5 milliliters per liter.
- Examples of some suitable complexing agents include Rochelle salts, ethylene diamine tetraacetic acid, the sodium (mono-, di-, tri-, and tetra-sodium) salts of ethylene diamine tetraacetic acid, nitrilo tetraacetic acid and its alkali salts, gluconic acid, gluconates, triethanol amine, glucono (gamma)-lactone, modified ethylene diamine acetates such as N-hydroxy ethyl ethylene diamine triacetate.
- a number of other suitable cupric complexing agents are suggested in U.S. Pat. Nos.
- the preferred complexing agents are ethylene diamine tetraacetic acid and the alkali metal salts thereof.
- the amount of complexing agent employed is typically about 25 to about 50 grams per liter.
- the plating bath can also include a surfactant which assists in wetting the surface to be coated.
- a surfactant is, for instance, an organic phosphate ester, available under the trade designation “Gafac RE-610”.
- the surfactant if present, is used in amounts from about 0.01 to about 0.3 grams per liter.
- the pH of the bath is generally controlled, for instance, by the addition of a basic compound, such as sodium hydroxide or potassium hydroxide in the desired amount to achieve the desired pH.
- a basic compound such as sodium hydroxide or potassium hydroxide
- the typical pH of the copper electroless plating bath is between 11.5 and 12.0, and more typically between 11.7 and 11.9.
- the plating bath can include other minor additives as is known in the art.
- the typical plating baths employed have a specific gravity within the range of 1.06 to 1.08. Moreover, the temperature of the bath is typically maintained between about 70° C. and 80° C., more typically between about 70° C. and 76° C., and preferably about 72° C. to about 75° C.
- the copper electroless plating bath typically contains about 5 to about 11 ppm, and more typically about 5 to about 8 ppm of cyanide ions.
- cyanide ions include the alkali metal, alkaline earth metal, and ammonium cyanides, with sodium cyanide being a more typical example.
- the electroless plating bath typically has an oxygen content of not lower than 1.5 ppm below saturation, and more typically an oxygen content of not lower than 1.0 ppm below saturation.
- Plating from the copper electroless plating bath generally continues from about 8 to about 20 hours, or until the desired thickness of copper film is achieved, which is typically about 350 micro inches to about 1850 micro inches.
- any copper plating either major surface may be planarized by any standard technique including chemical mechanical planarization (CMP).
- the plated through via will provide, after removal of the photoresist, a complete and uninterrupted conductive layer around through hole 8 .
- the remaining portions of the photoresist layer are removed, preferably by stripping the photoresist with a suitable solvent known in the art such as propylene carbonate, sodium carbonate, benzyl alcohol, or sodium hydroxide. Other removal techniques such as laser ablation and mechanical removal or combinations thereof, may also be employed to remove the photoresist layer.
- a suitable solvent known in the art such as propylene carbonate, sodium carbonate, benzyl alcohol, or sodium hydroxide.
- Other removal techniques such as laser ablation and mechanical removal or combinations thereof, may also be employed to remove the photoresist layer.
- the exposed areas of the first electrically conductive layer on the surfaces of base member 13 serve as one or more contact pad areas 34 . In addition to the exposed contact pad areas, it is also possible to expose one or more areas on base member 13 , depending on operational requirements for the final product. This area is a land segment which in turn surrounds through hole 8 and may serve to interconnect upper and lower layers of circuitry and also internal conductive planes such as 5 ,
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Abstract
A circuitized semiconductor substrate comprising a layer of dielectric material having holes therethrough, a catalyst seed layer lining the walls of the holes along the surface of the dielectric material, and a nickel layer in the openings and a layer of copper above the nickel layer, along with a method for its fabrication. The invention also provides copper-nickel laminate PTH barrels and methods for their fabrication.
Description
- The present invention relates to circuitized printed wiring board structures and especially to via barrels having enhanced copper adhesion. The enhanced adhesiveness of the copper plating provides improved performance in high temperature assembly operations. The present invention also provides a method for fabricating via barrels plated with highly adherent copper.
- In the manufacture of printed circuit boards, sometimes known as printed wiring boards, it is now commonplace to produce printed circuitry on both sides of a planar rigid or flexible insulating substrate. Of increased importance is the manufacture of multilayer printed circuits. In these products, the board consists of parallel, planar, alternating innerlayers of insulating substrate material and conductive metal. The exposed outer sides of the laminated structure are provided with circuit patterns as with double-sided boards, and the metal innerlayers may themselves contain circuit patterns.
- In double-sided and multilayer printed circuit boards, it is necessary to provide conductive interconnection between or among the various layers or sides of the board containing conductive circuitry. This is commonly achieved by providing metallized, conductive thru-holes in the board communicating with the sides and layers requiring electrical interconnection. For some applications, it is desired that electrical connection be made with up to all of the conductive layers. In such case, thru-holes are provided through the entire thickness of the board. For other applications, it is desired to provide electrical connection between the circuitry on one face of the board and one or more of the inner circuit layers. In those cases, blind via, passing only part way through the board are provided. For purposes of this application, the terms “thru-hole,” “blind via,” and “via” are used interchangeably.
- To provide the desired circuit pattern on the board, the art has developed a variety of manufacturing sequences, many of which fall into the broad categories of “subtractive” or “additive” techniques. Common to subtractive processes is the need to etch away (or subtract) metal to expose substrate surface in areas where no circuitry is desired. Additive processes, on the other hand, begin with exposed substrate surfaces (or thin commoning metallization layers for additive electroplate) and build up thereon metallization in desired areas, the desired areas being those not masked by a previously-applied pattern of plating resist material (e.g., photoresist in positive pattern).
- Typically, via holes are drilled or punched into or through the board structure at desired locations. Drilling or punching provides newly-exposed surfaces including via barrel surfaces and via peripheral entry surfaces. The dielectric substrate, comprising a top surface, a bottom surface, and at least one exposed via hole surface, consisting partly or entirely of insulating material, is then metallized, generally by utilization of electroless metal depositing techniques.
- In the manufacture of circuitized printed wiring board carrier structures, a dielectric sheet material is employed as the substrate. The substrate typically is an organic material, such as fiberglass-reinforced epoxy resin (FR4), polytetrafluoroethylene, etc. Since the dielectric substrate is nonconductive, in order to plate on the substrate, the substrate must be seeded or catalyzed prior to the deposition of metal onto the substrate. The electroless plating of copper onto a substrate is well-known in the art. For instance, an electroless or autocatalytic copper plating bath usually contains a cupric salt, a reducing agent for the cupric salt, a chelating or complexing agent, and a pH adjustor. In addition, if the surface being plated is not already catalytic for the deposition of the desired metal, a suitable catalyst is deposited onto the surface prior to contact with the plating bath. Among the more widely employed procedures for catalyzing a surface is the use of stannous chloride sensitizing solution and a palladium chloride activator to form a layer of metallic palladium particles.
- Copper is not highly adherent to the materials typically used as the dielectric substrate. The deposited copper is generally anchored to the exposed inner copper layers more than the dielectric. During subsequent process steps, especially thermal cycling, the copper “barrel” has a tendency to crack or delaminate, causing open circuits. Therefore a requirement exists for means to increase the bonding strength of the copper to the substrate.
- The present invention provides the desired increased durability of via barrels without the requirement for many of the additional processing steps and materials used in prior art solutions. For example, Takahashi et al. (U.S. Pat. No. 5,309,632) require a double resist process and the application of an adhesive layer to the entire board surface. Their method also plates nickel over the entire board surface and then strip the nickel in excess of the circuitization.
- It is known in the prior art to provide a layer of nickel over substantially the entire surface of the wiring board, print copper circuitization over the nickel, and then to strip excess nickel. Examples of this practice include Cane (U.S. Pat. No. 5,648,125). Stripping of Ni after application of Cu results in a line substantially trapezoidal in cross-section, with portions of the Cu wiring cantilevered, unstably over the Ni. In addition to plating Ni only where circuitization is to be invoked, the process of the present invention results in lines of substantially rectangular cross-section and thus a more stable bonding of the Cu.
- Another disadvantage of prior art methods is exemplified by Knopp (U.S. Pat. No. 5,758,412) where the thickness of the underplated metal is too thin to provide circuitization robustness against subsequent high temperature assembly steps.
- The present invention provides via barrels exhibiting high copper to substrate adhesion. The present invention makes possible via barrels that survive the thermal stresses of high temperature assembly and have a longer thermal cycle life than bare copper barrels.
- More specifically, the present invention provides via barrels which comprise: a wiring board of dielectric material wherein a plurality of via are defined; a catalyst seed layer located on the inner surface of the via within the dielectric material; a layer of nickel deposited on top of the catalyst seed layer; and a layer of copper plating in the openings and over the layer of nickel.
- It is an aspect of the invention to provide more robust metallization of via barrels by providing multiple metallization layers.
- It is an aspect of the invention to provide more robust metallization of via barrels by providing metallization, of via barrel surfaces including via peripheral entry surfaces, and providing metallization of via surfaces continuous with metallization of the top and bottom surfaces and the conductive layers of the dielectric substrate.
- It is an aspect of the invention to provide more robust metallization of via barrels by providing a circuitized printed wiring board comprising a dielectric substrate having a top surface, and a bottom surface, and at least one via, the at least one via having a via barrel surface and at least one via peripheral entry surface; a first metallization layer deposited on the via barrel surface and the at least one via peripheral entry surface of the at least one via, the top surface, and the bottom surface of the dielectric substrate; a second metallization layer deposited on the first metallization layer on the via barrel surface and the at least one via peripheral entry surface of the at least one via, and selectively deposited on the first metallization layer on the top surface and the bottom surface of said dielectric substrate; and a third metallization layer deposited on the second metallization layer on the first metallization layer on the via barrel surface and the at least one via peripheral entry surface of the at least one via, and selectively deposited on the second metallization layer on the first metallization layer on the top surface and the bottom surface of the dielectric substrate.
- The present invention also relates to fabricating the above disclosed printed circuit board. The method comprises: providing a board having a top surface and a bottom surface and comprised of one or more layers of dielectric material and optionally one or more inner conductive layers which are optionally personalized by provision of a pattern such as a circuit pattern; depositing a catalyst seed layer on the layer of dielectric material; depositing a layer of nickel on top of the catalyst seed layer; and depositing a layer of copper plating over the layer of nickel.
- Metallization of the dielectric substrate comprises providing a first metallization layer termed a catalytic seed layer and is typically palladium and tin; providing a second metallization layer wherein the layer is chosen from the group VIII and Group IB transition metals and is typically nickel; and providing a third metallization layer, typically copper. Alternatively, the catalytic seed layer is thus termed and the nickel and copper layers are respectively termed the “first metallization” and the “second metallization.”
- Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.
- The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity.
- FIG. 1 is a schematic cross-section of base member;
- FIG. 2 is a schematic transverse section of base member following formation of through hole;
- FIG. 3 is a schematic cross-section of base member after contact with catalytic composition;
- FIG. 4 is a schematic cross-section of base member after application of photoresist;
- FIG. 5 is a schematic cross-section of base member after second metallization layer; and
- FIG. 6 is a schematic cross-section of base member after third metallization layer.
- Reference is made to the figures to illustrate selected embodiments and preferred modes of carrying out the invention. It is to be understood that the invention is not hereby limited to those aspects depicted in the figures.
- In FIG. 1, there is shown an electrically
insulative base member 13 which may be used in the present invention to produce a printed wiring board (described below). It is understood that the invention is not limited to the particular configuration shown in FIG. 1, as others are readily possible.Base member 13 includes first and secondconductive layers 1 and 3, which sandwich there between, first and seconddielectric layers conductive plane 5. In a preferred embodiment, each of the two conductive layers is comprised of copper or a well-known conductive material, each having a thickness from about 0.25 mils (0.0025 inches) to about 1.5 mils with the thickness of each preferably being about 0.25 mils. Preferably each of the two dielectric layers is comprised of fiberglass reinforced epoxy resin (FR4). - A typical FR-4 epoxy composition contains 70-90 parts of brominated polyglycidyl ether of bisphenol-A and 10-30 parts of tetrakis(hydroxyphenyl)ethane tetraglycidyl ether cured with 3 to 4 parts of dicyandiamide, and 0.2 to 0.4 parts of a tertiary amine, all parts being parts by weight per 100 parts of resin solids.
- Another typical FR-4 epoxy composition contains: a) about 25 to about 30 parts by weight of a tetrabrominated diglycidyl ether of bisphenol-A having an epoxy equivalent weight of about 350 to about 450; b) about 10 to about 15 parts by weight of a tetrabrominated diglycidyl ether of bisphenol-A having an epoxy equivalent weight of about 600 to about 750; and c) about 55 to about 65 parts by weight of at least one epoxidized non-linear novolak, having at least terminal epoxy groups, along with suitable curing and/or hardening agents.
- Another typical FR-4 epoxy composition contains about 70 to about 90 parts of brominated polyglycidyl ether of bisphenol-A, and 10 to 30 parts of tetrakis (hydroxyphenyl) ethane tetraglycidyl ether cured with 0.8 to 1 part of 2-methyl imidazole.
- Still another FR-4 epoxy composition employs tetrabromo bisphenol-A as the curing agent, along with 2-methyl imidazole as the catalyst.
- In alternative embodiments, a wide variety of dielectric (non-conductive) substrates can be employed and, as described in the prior art, include thermoplastic and thermosetting resins. Typical thermosetting polymeric materials include epoxy, phenolic based materials, and polyamides. The dielectric materials may be molded articles of the polymers containing fillers and/or reinforcing agents, such as glass-filled epoxy or phenolic based materials. Examples of some phenolic type materials include copolymers of phenol, resorcinol and cresol. Examples of some suitable thermoplastic polymeric materials include polyolefins, such as polypropylene, polysulfones, polycarbonates, nitrile rubbers, ABS polymers and fluorinated polymeric materials such as polytetrafluoroethylene.
- In preferred embodiments, comprising FR4, each dielectric layer possesses a thickness of from about 2 mils to about 20 mils. Thicknesses less than about 2 mils for this particular material may be undesirable because the resulting structure may be flimsy and difficult to handle during subsequent manufacturing processes. Thicknesses greater than about 20 mils may be undesirable because such thick dielectric layers, in addition to requiring relatively large conductor line widths and thicknesses, also may prevent optimum package electrical performance.
- Sandwiched between
dielectric layers conductive plane 5, preferably of copper or other well-known conductive material and possessing a thickness of preferably within the range of about 0.125 mils to about 2.5 mils. The thicknesses forplane 5 of less than about 0.125 mils may prove undesirable should the resulting structure by subjected to relatively high temperatures. Additionally, thicknesses greater than about 2.5 mils may prove undesirable because of the additional time necessary to form such layers using conventional plating techniques and associated difficulties with line width control. - The resulting structure shown in FIG. 1 thus preferably possesses a thickness within the range of about 4.7 mils to about 400 mils. The preferred thickness is governed by the desired number of signal planes.
-
Conductive layers 1 and 3 anddielectric layers conductive plane 5 using a lamination process, such a process known in the art and further description is not believed necessary. -
Base member 13 is thus shown to include at least two surfaces, afirst surface 6, and asecond surface 7. - Although two conductive layers and two dielectric layers are shown for
base member 13, it is understood that the invention is not limited thereto. Specifically, it is only necessary to provide one such conductive layer and one such dielectric layer while still attaining the advantageous results taught herein. At least two layers of each are used when it is desired to incorporate an internal conductive plane (e.g., power, ground or signal) as part of the final structure. Understandably, several dielectric layers and corresponding internal conductive planes may be utilized, depending on operational requirements for the finished product. - In FIG. 2,
opening 8 having an internal wall surface or viabarrel surface 9 and having a via peripheral entry surface orknee 9A is formed substantially throughbase member 13. Although only one opening is shown formed inbase member 13, it is understood that multiple openings may be formed inbase member 13 depending on the ultimate electrical requirements of the circuitized substrate.Opening 8, which may be any type of via, may be formed by mechanical drilling although other hole forming techniques such as punching and laser drilling can be used. The minimum diameter ofopening 8 is governed by the depth of the hole such that an approximately unitary aspect ratio (hole diameter/depth) is achieved. The upper limit of hole diameter is a function of the purpose of the hole. - In the next step, it is preferred to provide a first-
metallization layer 10 on thesurfaces base member 13, and oninternal wall 9 ofopening 8 to act as a catalyst for future metallization layers. - FIG. 3 shows
base member 13 after contact with a composition containing a catalytic composition capable of initiating an electroless plating process providing acatalyst seed layer 10. Thecatalyst seed layer 10 is alternatively referred to as the first metallization layer. The compositions contain a metal that can directly provide the catalytic sites, or serve as a precursor which leads to the catalytic sites. The metal present may be in the elemental form, an alloy, or compound, or mixtures thereof. The preferred metal catalysts are precious metals, such as gold, palladium, and platinum. A typical palladium composition contains about 1.2 to about 2.5 grams per liter of a palladium salt, which is preferably PdCl2, about 80 to about 150 grams per liter of a stannous salt, which is preferably SnCl2.2H2O, and about 100 to about 150 milliliters per liter of an acid which is preferably HCl. When HCl is provided in the form of a 37% HCl solution, about 280 to about 360 milliliters of the HCl solution is preferably employed. The most preferred composition contains about 1.5 grams per liter of PdCl2 and about 280 milliliters per liter of 37% HCl. The composition is usually maintained at a temperature of about 65±10° F. A typical triple-seeder process is disclosed, for instance, in Alpaugh et al U.S. Pat. No. 4,525,390, disclosure of which is incorporated herein by reference. - Subsequently, the substrate can be treated with an acid or alkaline accelerator such as a 2% NaOH solution to remove excess tin which is typically deposited along with the Pd catalyst. This step usually takes about 1 to about 5 minutes and, more typically, about 1 to about 2 minutes.
- The substrates can then be dried, such as by being vacuum dried in an oven for 30 minutes at a temperature of about 100° C. In the drying operation, all the water is driven off irreversibly from the colloidal particles, leaving a shell of oxygen in the form of insoluble tin oxide.
- Moreover, if desired, prior to providing the
catalyst seed layer 10, thedielectric layers - Reten 210 is in powder form and is a copolymer of acrylamide and beta-methacryloxyethyltrimethylammonium methyl sulfate, of which a 1% solution has a Brookfield viscosity of 600-1000 cps. Reten 220 is also in powder form and consists of the same monomers as Reten 210, but its 1% solution has a Brookfield viscosity of 800-1200 cps. The molecular weights of the Reten polymers are usually relatively high and vary from about 50,000 to about 1,000,000 or more. The quaternary ammonium groups provide the number of positive charges of the polymer.
- In the various aspects of the present invention, the ionic copolymer is employed as a dilute acidic solution of about 0.01% to about 1% by weight, and preferably about 0.05% to about 0.5% by weight of the copolymer. The acid contained in the solution is preferably H2SO4, and the pH value of the solution is between 0 and about 3. The use of a low pH value is preferred to obtain a relatively low viscosity of the copolymer solution to facilitate application of the polymer. The treatment with the ionic copolymer is generally about 1 minute to about 10 minutes, and preferably about 1 minute to about 2 minutes, and takes place at about room temperature.
- The multifunctional copolymer, having a very good adhesion to the substrate surface, provides the surface with a charge opposite from that associated with the
seed particles 10 applied to the substrate. This difference in polarity provides for electrostatic attraction of the seed particles. After the substrate is brought into contact with the ionic copolymer composition, the substrate is rinsed to remove any excess polymer not adhering to the substrate surface. - A layer31 of photoimaging (photoresist) material is then applied to the surfaces of
member 13 over the first metallization layer. In one example, the layer of photoresist possessed a thickness of from about 0.3 mils to about 2.0 mils. A preferred material is a positive-acting photoresist, various examples being known in the art, including T168 photoresist available from the E. I. du Pont de Nemours Corporation under this trade designation. A positive-acting photoresists, when applied and exposed through a suitable photomask, undergo a physical and chemical change in the exposed areas that render these areas insoluble to the subsequent developing solution which is to be applied thereto. Following exposure, the resist-coatedbase member 13 is immersed in developing solution (e.g., benzyl alcohol or propylene carbonate), which allows the unexposed areas to be removed without excessive impact on the hardened, exposed area. Baking or other processes may be used to further harden the remaining, exposed portions, if desired. With positive-acting photoresists, the portions developed away form the openings to the catalyzed laminated surface for subsequent plating - In FIG. 4,
base member 13 is shown following the above exposure and removal (developing) operations. As such, only portions of photoresist layer 31 remain. These portions are represented by the numeral 11. It is understood that the removed portions of the photoresist in turn result inopenings 35 which, in turn, expose preselected areas on the respective surfaces on which circuitization is to eventually occur. Thus a predetermined pattern on both surfaces is provided. Furthermore, it is understood that the photomask is designed such that theinternal wall 9 of throughholes 8 are not exposed. - As seen next, in FIG. 5, a
second metallization layer 12 is deposited into the photoresist openings formed onbase member 13 and in throughhole 8. The secondmetallization conductive layer 12 comprises nickel. The thickness of this second metallization conductive layer may be from about 0.1 mils to about 0.15 mils preferably about 0.12 mils to about 0.13 mils. The nickel is deposited on the seed layer by immersing into an electroless nickel plating process as known in the industry. Plating chemistries for electroless nickel plating are well known in the industry and need not be described herein in any detail. - Typical methods for depositing nickel on the surface or surfaces of a substrate involve immersing the substrate in an aqueous solution comprising as ingredients a source of nickel ions, a soluble reducing agent for the nickel, a metal complexing agent and pH adjusting agents under conditions effective to bring about electroless deposition of nickel on the surface or surfaces by means of chemical reduction.
- Where the invention is practiced in conjunction with imaging printing of copper lines (see co-pending application Ser. No. 09/357,574, assigned to assignee of present invention), it is important according to the present invention that the nickel plating be carried out after the development of the layer of photoimageable material since it eliminates the possibility of electrical leakage between lines. If plated before the layer of photoimageable material, the presence of nickel beneath the layer of photoimageable material could result in electrical leakage between lines, especially when spaced relatively close to each other. In addition, the nickel bath is generally more active than a copper plating bath. Accordingly, circuitization yields are higher because the line will have fewer defects.
- The second metallization layer is deposited by conventional plating methods for electroless plating. These processes typically have their own in-line seeding means because typically it is desired to plate nickel only on another metal surface. Crucial to the present invention is that the typical precleaning/preconditioning steps normally associated with this electroless nickel process are not performed. These processes remove portions of the first metallization (seed) layer. The present invention achieves the plating of nickel directly on the laminate surface. Use of precleaning or preconditioning steps removes portions of the seed particles thus causing skip plating on the laminate. Where the metal adheres to only portions of the inner surface of the hole, the adhesion is poor resulting is shortened mean time between failure.
- As seen in next FIG. 6, a
third metallization layer 14 is deposited on thesecond metallization layer 12. This metallization layer is typically plated to the same height as the top of the photoresist, although not always. Generally, the photoresist thickness is matched to the final desired conductor thickness. This aids post plating processing, if needed, for planarizing to remove plated nodules or extraneous plating above the desired conductor height should it occur. - Typically, application of the third metallization layer follows substantially immediately after application of the second metallization layer. Alternatively, where it is desired to temporarily store the partial assembly, obtained through the second metallization step, it is necessary to clean the oxide or other inappropriate material coating the nickel prior to application of the third metallization layer. This cleaning may be accomplished with industry standard techniques.
- It has been found that nickel, comprising the second metallization layer provides for enhanced adhesion of the copper to the substrate.
Copper 14 is plated on the inner surfaces of the holes over thenickel layer 12 from an electroless plating bath to provide the desired PTH barrel thickness. Examples of suitable electroless copper plating baths can be found in U.S. Pat. Nos. 5,509,557, 4,707,377 and 4,904,506, disclosures of which are incorporated herein by reference. - The copper electroless plating bath employed is generally an aqueous composition, which contains a source of cupric ion, a complexing agent for the cupric ion, and a pH adjustor, in addition to the cyanide ion source and oxygen. In addition, the plating bath also preferably includes a surface-active agent. The cupric ion source generally used is a cupric sulfate or a cupric salt of the complexing agent to be employed. The cupric ion source in the electroless plating bath is typically employed in amounts of about 9 to about 14, and more typically about 10 to about 12 grams per liter, calculated as CuSo4.5H2O.
- The most common reducing agent employed is formaldehyde. Examples of some other reducing agents include formaldehyde precursors or formaldehyde homopolymers, such as paraformaldehyde, trioxane, and gloxal; borohydrides such as alkali metal borohydrides (sodium and potassium borohydrides) and substituted borohydrides such as sodium trimethoxy borohydride; boranes such as amine borane (isopropyl amine borane and morpholine borane); and hypophosphite reducing agents. The reducing agent is generally present in amounts from about 1 to about 4 milliliters per liter, and more typically from about 2 to about 2.5 milliliters per liter.
- Examples of some suitable complexing agents include Rochelle salts, ethylene diamine tetraacetic acid, the sodium (mono-, di-, tri-, and tetra-sodium) salts of ethylene diamine tetraacetic acid, nitrilo tetraacetic acid and its alkali salts, gluconic acid, gluconates, triethanol amine, glucono (gamma)-lactone, modified ethylene diamine acetates such as N-hydroxy ethyl ethylene diamine triacetate. In addition, a number of other suitable cupric complexing agents are suggested in U.S. Pat. Nos. 2,996,408; 3,075,856; 3,076,855 and 2,938,805. The preferred complexing agents are ethylene diamine tetraacetic acid and the alkali metal salts thereof. The amount of complexing agent employed is typically about 25 to about 50 grams per liter.
- The plating bath can also include a surfactant which assists in wetting the surface to be coated. A satisfactory surfactant is, for instance, an organic phosphate ester, available under the trade designation “Gafac RE-610”. Generally, the surfactant, if present, is used in amounts from about 0.01 to about 0.3 grams per liter.
- In addition, the pH of the bath is generally controlled, for instance, by the addition of a basic compound, such as sodium hydroxide or potassium hydroxide in the desired amount to achieve the desired pH. The typical pH of the copper electroless plating bath is between 11.5 and 12.0, and more typically between 11.7 and 11.9. In addition, the plating bath can include other minor additives as is known in the art.
- The typical plating baths employed have a specific gravity within the range of 1.06 to 1.08. Moreover, the temperature of the bath is typically maintained between about 70° C. and 80° C., more typically between about 70° C. and 76° C., and preferably about 72° C. to about 75° C.
- The copper electroless plating bath typically contains about 5 to about 11 ppm, and more typically about 5 to about 8 ppm of cyanide ions. Examples of some cyanides are the alkali metal, alkaline earth metal, and ammonium cyanides, with sodium cyanide being a more typical example.
- The electroless plating bath typically has an oxygen content of not lower than 1.5 ppm below saturation, and more typically an oxygen content of not lower than 1.0 ppm below saturation.
- Plating from the copper electroless plating bath generally continues from about 8 to about 20 hours, or until the desired thickness of copper film is achieved, which is typically about 350 micro inches to about 1850 micro inches. Where desired, any copper plating either major surface may be planarized by any standard technique including chemical mechanical planarization (CMP).
- Significantly, it can be seen that the plated through via will provide, after removal of the photoresist, a complete and uninterrupted conductive layer around through
hole 8. - In FIG. 7, the remaining portions of the photoresist layer are removed, preferably by stripping the photoresist with a suitable solvent known in the art such as propylene carbonate, sodium carbonate, benzyl alcohol, or sodium hydroxide. Other removal techniques such as laser ablation and mechanical removal or combinations thereof, may also be employed to remove the photoresist layer. In one example, the exposed areas of the first electrically conductive layer on the surfaces of
base member 13 serve as one or morecontact pad areas 34. In addition to the exposed contact pad areas, it is also possible to expose one or more areas onbase member 13, depending on operational requirements for the final product. This area is a land segment which in turn surrounds throughhole 8 and may serve to interconnect upper and lower layers of circuitry and also internal conductive planes such as 5, if desired. - It will, therefore, be appreciated by those skilled in the art having the benefit of this disclosure that this invention is capable of producing printed wiring boards having highly reliable plated through holes. Furthermore, it is to be understood that the form of the invention shown and described is to be taken as presently preferred embodiments. Various modifications and changes may be made to each and every processing step as would be obvious to a person skilled in the art having the benefit of this disclosure. It is intended that the following claims be interpreted to embrace all such modifications and changes and, accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.
Claims (34)
1. A circuitized printed wiring board comprising:
a dielectric substrate provided with a pattern of vias;
a first metallization layer located on the inner surface of said pattern of vias;
a layer of Ni deposited on said first layer; and
a layer of Cu plated on said Ni layer.
2. The circuitized printed wiring board of claim 1 wherein said dielectric substrate comprises epoxy resin optionally reinforced.
3. The circuitized printed wiring board of claim 1 wherein said first metallization layer is deposited from a palladium/tin colloidal suspension.
4. The circuitized printed wiring board of claim 1 wherein the layer of nickel is about 1 to about 5 microns thick.
5. The printed wiring board of claim 1 wherein the layer of nickel is about 2.5 to about 3.5 microns thick.
6. The printed wiring board of claim 1 wherein the layer of dielectric material has a roughened surface.
7. A method for fabricating a circuitized printed wiring board comprising:
providing at least one layer of dielectric material;
providing a pattern of vias in said dielectric material;
depositing a catalyst seed layer on said layer of dielectric material;
depositing and patterning a photoresist layer on said seed layer;
depositing a layer of nickel on top of said catalyst seed layer; and
depositing a layer of copper plating over said layer of nickel.
8. The method of claim 7 wherein the layer of dielectric material comprises epoxy resin optionally reinforced.
9. The method of claim 7 wherein the catalyst seed layer is deposited from a palladium/tin colloidal suspension.
10. The method of claim 7 wherein the nickel layer is deposited to a thickness of about 1 to about 5 microns.
11. The method of claim 7 wherein the nickel layer is deposited to a thickness of about 2.5 to about 3.5 microns.
12. The method of claim 7 wherein the copper is deposited by electroless plating
13. The method of claim 7 , wherein electroless plating comprises:
providing a copper electroless plating bath;
providing a dielectric material having PTH holes plated with nickel; and
immersing said dielectric material in said electroless plating bath.
14. The method of claim 13 wherein said electroless plating bath comprises oxygen not lower than 1.5 ppm below saturation
15. The method of claim 13 wherein said electroless plating bath comprises oxygen not lower than 1.0 ppm below saturation.
16. The method of claim 13 wherein the pH of said electroless plating bath is adjusted to the range from about 11.5 to about 12.0.
17. The method of claim 13 wherein the pH of said electroless plating bath is adjusted to the range from about 11.7 to about 11.9.
18. The method of claim 13 wherein said electroless plating bath comprises cyanide ion comprises from about 5 to about 11 ppm., and more typically about 5 to about 8 ppm of cyanide ions
19. The method of claim 13 wherein said cyanide ion comprises from about 5 to about 8 ppm.
20. The method of claim 13 wherein the specific gravity of said electroless plating bath is within the range of 1.06 to 1.08
21. The method of claim 13 wherein the temperature of said electroless plating bath is maintained between about 70° C. and 80° C.
22. The method of claim 13 wherein the temperature of said electroless plating bath is maintained between about 72° C. and 75° C.
23. A copper-nickel laminate via barrel obtained by the method of claim 7 .
24. A circuitized printed wiring board obtained by the method of claim 7 .
25. A circuitized printed wiring board comprising:
a dielectric substrate having a top surface, and a bottom surface, and at least one via, said at least one via having a via barrel surface and at least one via peripheral entry surface;
a first metallization layer deposited on said via barrel surface and said at least one via peripheral entry surface of said at least one via, said top surface, and said bottom surface of said dielectric substrate;
a second metallization layer deposited on said first metallization layer on said via barrel surface and said at least one via peripheral entry surface of said at least one via, and selectively deposited on said first metallization layer on said top surface and said bottom surface of said dielectric substrate; and
a third metallization layer deposited on said second metallization layer on said first metallization layer on said via barrel surface and said at least one via peripheral entry surface of said at least one via, and selectively deposited on said second metallization layer on said first metallization layer on said top surface and said bottom surface of said dielectric substrate.
26. The circuitized printed wiring board of claim 25 , wherein said first metallization layer is a catalytic seed layer.
27. The circuitized printed wiring board of claim 26 , wherein said catalytic seed layer is chosen from the group consisting of palladium and tin.
28. The circuitized printed wiring board of claim 26 , wherein said second metallization layer is chosen from the group consisting of Group VIII and Group IB transition metals.
29. The circuitized printed wiring board of claim 26 , wherein said third metallization layer is chosen from the group consisting of manganese, iron, cobalt, nickel, copper, palladium, platinum, silver, and gold.
30. A method for fabricating a circuitized printed circuit wiring board comprising:
providing a substrate having a top surface and a bottom surface;
providing at least one via having a barrel surface and at least one via peripheral entry surface in said substrate;
depositing a catalyst seed layer on said via barrel surface and said at least one via peripheral entry surface of said at least one via, said top surface and said bottom surface of said substrate;
providing a resist layer on selected areas over said catalyst seed layer on said top surface and said bottom surface of said substrate;
depositing a first metallization layer over areas of catalyst seed layer not protected by said protective resist layer on said top surface and said bottom surface of said substrate, and said via barrel surface and said at least one via peripheral entry surface of said at least one via; and
depositing a second metallization layer over said first metallization layer.
31. The method of claim 30 wherein said step of depositing a catalyst seed layer further includes processing selected from the group consisting of colloidal suspension, ionic solution, and organometallic solution.
32. The method of claim 30 wherein said catalytic seed layer is palladium.
33. The method of claim 32 wherein said first metallization layer is nickel.
34. The method of claim 33 wherein said second metallization layer is copper.
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US09/795,332 US6630743B2 (en) | 2001-02-27 | 2001-02-27 | Copper plated PTH barrels and methods for fabricating |
US10/461,516 US20030209799A1 (en) | 2001-02-27 | 2003-06-16 | Copper plated PTH barrels and methods for fabricating |
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US10/461,516 Abandoned US20030209799A1 (en) | 2001-02-27 | 2003-06-16 | Copper plated PTH barrels and methods for fabricating |
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Also Published As
Publication number | Publication date |
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US6630743B2 (en) | 2003-10-07 |
US20020195716A1 (en) | 2002-12-26 |
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