Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/18—Electroplating using modulated, pulsed or reversing current
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D21/00—Processes for servicing or operating cells for electrolytic coating
  • C25D21/12—Process control or regulation
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/38—Electroplating: Baths therefor from solutions of copper
• • 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
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/11—Printed elements for providing electric connections to or between printed circuits
  • H05K1/115—Via connections; Lands around holes or via connections
• • 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
  • H05K3/423—Plated through-holes or plated via connections characterised by electroplating method
• • 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
  • H05K2201/09—Shape and layout
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/095—Conductive through-holes or vias
  • H05K2201/09563—Metal filled via
• • 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
  • H05K2203/1476—Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning
• • 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
  • H05K2203/1492—Periodical treatments, e.g. pulse plating of through-holes
• • 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

Definitions

• the present invention relates to a galvanic process for filling through-holes with metals.
• the process is particularly suitable for filling through-holes of printed circuit boards with copper.
• the process provides durable fillings even in the case of small hole diameters, undesired inclusions in the through-hole can be avoided. Furthermore, the filling exhibits very good thermal conductivity.
• Printed circuit boards having these properties are generally referred to as printed circuit boards with high integration density (so-called High Density Inter ⁇ connection or HDI).
• the main focus of the present invention is the filling of through-holes in printed circuit boards which go through the entire board (Plated Through Hole, PTH) and of interior vias (buried vias).
• the process is suitable for filling through-holes in the most different workpieces, in particular board-shaped workpieces and board-shaped electric circuit carriers containing through-holes.
• the closing of the through-holes is necessary inter alia so as to prevent the deposition of solder on the components, to achieve a high integration density and to improve the electrical properties.
• in- elusions of air, solvent, etc.
• in the holes might occur during the laminating of the next build-up layer, which inclusions later on in the case of thermal stresses lead to bulges and, consequently, cracks in the next layer.
• the holes are filled using a specially adjusted solder resist. They have the advantage to offer that in the case of high integration density no impairment is caused in the resolution by the via filler which necessarily pro ⁇ trudes like a rivet head.
• the danger of sol- vent inclusions which can abruptly evaporate in subsequent process steps, such as tinning, and, thus, tear open the cover.
• dielectrics such as resin-coated copper foils (RCC) or photo-dielectric liquid or dry films are used.
• EP 0 645 950 B1 describes a process for producing multi-layered circuit sub ⁇ strates.
• thermosetting resins are used cho ⁇ sen from the group consisting of phenolic resin and epoxy resin.
• a conductive substance at least one metal powder chosen from the group consisting of silver, nickel, copper and an alloy thereof is added to the resin.
• the plugging is done after the printed circuit board has been drilled and the drill holes finally metallized, however, before the structuring.
• the plugging paste has been cured, the latter is me ⁇ chanically leveled since due to the filling process it exhibits a slight rivet head.
• a metallization of the paste with copper is subsequently carried out so that a continuous copper layer is created as final layer. To put it simply, the fol ⁇ lowing steps are required:
• EP 1 194 023 A1 describes the manufacturing of HDI printed circuit boards by filling through-holes with conductive pastes, wherein the curing of the paste can occur at the same time as the molding of the basic material so that an electric contact of interior layers results.
• the object of the present invention to develop a process which avoids the disadvantages mentioned and provides a simple process for reliably filling the through-holes of a workpiece with nearly no inclusions.
• the process can be used in particular for filling the through-holes in printed-circuit boards with copper.
• a further object of the invention is to achieve a high performance in the electro ⁇ lytic metallization.
• the object is achieved by using the inventive process for filling through-holes of a workpiece with metals comprising the following process steps:
• step (ii) Further bringing in contact the workpiece with a metal- deposition electrolyte and applying a voltage between the workpiece and at least one anode so that a current flow is supplied to the workpiece, wherein the through-holes obtained in step (i) which are completely or almost completely divided into to halves are filled by the metal up to the desired degree in accordance with Fig. 2.
• the present invention is based on the idea to create in the first step of a special deposition technique two holes from the through-hole by completely or almost completely filling the hole center, which two holes are each closed at one end close to the hole center (cf. Fig. 1).
• the shape of the deposit in the area of the through-hole center can be V-shaped, as is shown in Fig. 1a, or it can be in the shape of a rounded narrow part (cf. Fig. 1b). This shape of the deposit can be achieved by increased scattering in the area of the through-hole center so that here an increased deposition of metal compared to the ends of the through-hole can be observed.
• blind holes In printed circuit board production, a preferred field of application of the present invention, these holes are also referred to as blind holes or blind vias.
• a sec ⁇ ond metallization step the thus created blind vias are then filled with metal (cf. Fig. 2). Processes for filling blind vias are actually known and described in the state of the art.
• EP 1 264 918 A1 describes an electrolytic copper deposition process which is particularly suitable for filing micro blind vias.
• the use of inert anodes in a dummy plating phase helps to maintain and improve the fillability of the electro ⁇ lyte.
• organic additives comprise brightening agents, wetting agents and further additives chosen from polyamides, polyamines, lactam alkoxylates, thiourea, oligomeric and polymeric phenazonium derivatives and amino-triphenylmethane dyes,
• the process serves for filing the through-holes in printed circuit boards with a maximum height of 3.5 mm, a preferred height of 0.025 - 1 mm and a particularly preferred height of 0.05 - 0.5 mm as well as a diameter of 1000 ⁇ m at most, preferably 30 - 300 ⁇ m and most preferably 60 - 150 ⁇ m.
• every electrolyte suitable for galvanic metal-deposition can be used, such as electrolytes for depositing gold, tin, nickel or alloys thereof.
• the pre ⁇ ferred metal is copper.
• Copper can be given into the electrolyte as copper sulfate pentahydrate (CuSO 4 x 5H2O) or as copper sulfate solution.
• the working range is between 15 - 75 g/l copper.
• Sulfuric acid H 2 SO 4
• the working range is be ⁇ tween 20 - 400 g/l, preferably 50 - 300 g/l.
• Chloride is added as sodium chloride (NaCI) or as hydrochloric acid solution (HCI).
• NaCI sodium chloride
• HCI hydrochloric acid solution
• the working range of chloride is between 20-200 mg/l, preferably 30-60 mg/l.
• the electrolyte preferably comprises brightening agents, leveling agents and wetting agents as organic additives.
• wetting agents are oxygen-containing, high-molecular compounds in concentrations of 0,005-20 g/l, preferably 0.01-5 g/l. Examples are given in Ta ⁇ ble 1 :
• sulfur-containing substances which are listed in Table 2:
• polymeric nitrogen compounds e.g. polyamines or polyam- ides
• nitrogen-containing sulfur compounds such as thiourea derivates or lactam alkoxylate, as described in DE 38 36 521 C2
• the concen ⁇ trations of the substances used are in a range from 0.1-100 ppm.
• polymeric phenazonium derivatives which are described in the patent DE 41 26 502 C1 , can be used.
• Further substances which are used for filling blind vias are coloring agents on the basis of an aminotriphenyl- methane structure such as malachite, rosalinine or crystal violet.
• inert anodes without and with redox system i.e. with Fe 2+/3+ system, for example
• concentration of iron(ll) ions is 1 - 15 g/l in general, preferably 8 - 12 g/l
• concentration of iron(lll) ions is 1 - 15 g/l in general and preferably 8 -12 g/l.
• DC and AC electrolytes also soluble anodes can be used.
• the metal is deposited not only in the through-holes but also on the surface of the substrate.
• the copper layer on the surface can be removed again using the etching processes known in printed circuit board production.
• solutions containing iron(lll) chloride are suitable.
• Reverse pulse plating was developed for the electrolytic deposition of copper in particular on printed circuit boards with a high aspect ratio and is described in DE 42 25 961 C2 and DE 27 39 427 A1 , for example. By using high current densities an improved surface distribution and scattering in the through-holes is achieved.
• the ratio of the duration of the at least one forward current pulse to the duration of the at least one reverse current pulse is adjusted to at least 5, preferably to at least 15 and more preferably to at least 18. This ratio can be adjusted to 75 at most and preferably to 50 at most. It is particularly preferred to adjust this ratio to about 20.
• the duration of the at least one forward current pulse can be adjusted to pref ⁇ erably at least 5 ms to 250 ms.
• the duration of the at least one reverse current pulse is preferably adjusted to 20 ms at most and most preferably to 1 - 10 ms.
• the peak current density of the at least one forward current pulse at the work- piece is preferably adjusted to a value of 15 A/dm 2 at most.
• Particularly prefer ⁇ able is a peak current density of the at least one forward current pulse at the workpiece of about 1.5 - 8 A/dm 2 in horizontal processes. In vertical processes the most preferred peak current density of the at least one forward current pulse at the workpiece is 2 A/dm 2 at most.
• the peak current density of the at least one reverse current pulse at the work piece will preferably be adjusted to a value of 60 A/dm 2 at most. Particularly preferred is a peak current density of the at least one reverse current pulse at the workpiece of about 30 - 50 A/dm 2 in horizontal processes. In vertical proc ⁇ esses the most preferred peak current density of the at least one forward cur ⁇ rent pulse at the workpiece is 3 - 10 A/dm 2 at most.
• the process comprises the following steps:
• a first voltage is applied between a first side of the workpiece and at least a first anode so that a first pulse reverse current is supplied to the first side of the workpiece, wherein in every cycle of this first pulse reverse current at least a first forward current pulse and at least a first reverse current pulse flow.
• a second voltage is applied between a second side of the workpiece and at least a second anode so that a second pulse reverse current is sup- plied to the second side of the workpiece, wherein in every cycle of this second pulse reverse current at least a second forward current pulse and at least a second reverse current pulse flow.
• the at least one first forward current pulse and the at least one first reverse current pulse, respectively can be offset relative to the at least one second forward current pulse and to the at least one second reverse current pulse, respectively.
• this offset between the first and second current pulses amounts to about 180°.
• the current flow in every cycle can comprise two forward current pulses, wherein between the two forward current pulses and a reverse current pulse a zero current interruption is provided.
• At least one parameter of the pulse reverse current can be varied, wherein this parameter is chosen from a group comprising the ratio of the duration of the forward current pulse to the duration of the reverse current pulse and the ratio of the peak current density of the forward current pulse to the peak current density of the reverse current pulse. It has been proven to be particularly advantageous to increase the ratio of the peak current density of the forward current pulse to the peak current den ⁇ sity of the reverse current pulse when metallizing the workpiece and/or to de- crease the ratio of the duration of the forward current pulse to the duration of the reverse current pulse.
• the lnpulse 2 modules of Atotech GmbH used for horizontal treatment of printed circuit boards have a gap of 15 mm between the nozzle holder and the cathode (workpiece) and a gap of 8 mm between anode and cathode.
• the surface of the printed circuit board Prior to metallization the surface of the printed circuit board is first of all cleansed for 45 seconds with the cleaner Cuprapro CF of Atotech Deutschland GmbH and then treated for 45 seconds with 5% sulfuric acid.
• the electrolytes used have the following composition.
• the concentration of the copper ions and the sulfuric acid is individually given in the tests.
• the metallization is carried out at a temperature of 4O 0 C.
• copper sulfate sulfuric acid chloride ions 50 mg/l iron(II): 10 g/I iron(lll): 2 g/l leveling agent lnpulse H6: 4 ml/I; brightening agent lnpulse H6: 7 ml/I leveling agent lnpulse HF: 4 ml/I; brightening agent lnpulse HF: 7 ml/l lnpulse leveling agent und brightening agent are products of Atotech
• the printed circuit board is at first treated for 30 minutes in a bath for elec ⁇ trolytic metallization with copper with the lnpulse H6 process and a pulse re- verse current process with the parameters according to Table 1a.
• a copper deposition in the through-holes as is shown in Fig. 1a is obtained.
• the printed circuit board is treated for a further 30 minutes in a second bath for electrolytic metallization with copper with the lnpulse HF process and a pulse reverse current process with the parameters according to Table 1b.
• a copper deposition in the through-holes as is shown in Fig. 2 is obtained.
• the printed circuit board is at first treated for 30 minutes in a bath for elec ⁇ trolytic metallization with copper with the lnpulse H6 process and a pulse re ⁇ verse current process with the parameters according to Table 2a.
• the printed circuit board is treated for a further 30 minutes in a second bath for electrolytic metallization with copper with the lnpulse HF process and a pulse reverse current process with the parameters according to Table 2b.
• the printed circuit board is treated for 60 minutes in a bath for electrolytic metallization with copper with the lnpulse HF process and a pulse reverse cur ⁇ rent process with the parameters according to Table 3.
• a printed circuit board having a through-hole diameter of 200 ⁇ m and a height of 300 ⁇ m is at first treated for 30 minutes in a bath for electrolytic metal- lization with copper with the lnpulse H6 process and a pulse reverse current process with the parameters according to Table 4a.
• the printed circuit board is treated for a further 30 minutes in a second bath for electrolytic metallization with copper with the lnpulse HF process and a pulse reverse current process with the parameters according to Table 4b. Then, the filling of the through-holes is complete. No inclusions are observed.
• the surface of the printed circuit board is at first cleansed for 3 minutes with an acid cleaner S of Atotech Deutschland GmbH and then treated for 60 seconds with 5% sulphuric acid.
• the electrolytes used have the following composition.
• the concentration of copper ions and sulfuric acid is individually given in the tests.
• the metallization is carried out at a temperature of 23°C.
• cuprapulse XP7 20 ml/I
• brightening agent Cuprapulse S3 1 ml/l leveling agent lnplate Dl: 15 ml/l
• brightening agent lnplate Dl 0,5 ml/I
• Cuprapulse and lnplate leveling agent and brightening agent are prod- ucts of Atotech Deutschland GmbH.
• a redox system is only used in the second step with the following com ⁇ position: iron(ll): 5 g/l iron(lll): 1 g/l
• the printed circuit board is at first treated for 90 minutes in a bath for electrolytic metallization with copper with the Cuprapulse XP7 process and a pulse reverse current process with the parameters according to Table 5a. Then, in a second step, the printed circuit board is treated for a further 85 minutes in a bath for electrolytic metallization with copper with the lnplate Dl process and a direct current with the parameters according to Table 5b. Then, the filling of the through-holes is complete. No inclusions are observed.
• the printed circuit board is at first treated for 90 minutes in a bath for electrolytic metallization with copper with the Cuprapulse XP7 process and a pulse reverse current process with the parameters according to Table 6a. Then, in a second step, the printed circuit board is treated for a further 85 minutes in a bath for electrolytic metallization with copper with the lnplate Dl process and a direct current with the parameters according to Table 6b. Then, the filling of the through-holes is complete. No inclusions are observed.
• the printed circuit board is at first treated for 90 minutes in a bath for electrolytic metallization with copper with the Cuprapulse XP7 process and a pulse reverse current process with the parameters according to Table 7a. Then, in a second step, the printed circuit board is treated for a further 85 minutes in a bath for electrolytic metallization with copper with the lnplate Dl process and a direct current with the parameters according to Table 7b. Then, the filling of the through-holes is complete. No inclusions are observed.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Manufacturing & Machinery (AREA)
• Automation & Control Theory (AREA)
• Printing Elements For Providing Electric Connections Between Printed Circuits (AREA)
• Electroplating Methods And Accessories (AREA)
• Manufacturing Of Printed Wiring (AREA)
• Non-Metallic Protective Coatings For Printed Circuits (AREA)

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Cited By (8)

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Citations (9)

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• 2004
  • 2004-09-20 DE DE102004045451A patent/DE102004045451B4/de not_active Expired - Fee Related
• 2005
  • 2005-08-23 TW TW094128784A patent/TWI370715B/zh not_active IP Right Cessation
  • 2005-08-30 DE DE602005011662T patent/DE602005011662D1/de not_active Expired - Lifetime
  • 2005-08-30 US US11/661,704 patent/US9445510B2/en active Active
  • 2005-08-30 KR KR1020077007033A patent/KR101222627B1/ko not_active Expired - Lifetime
  • 2005-08-30 JP JP2007531632A patent/JP5078142B2/ja not_active Expired - Lifetime
  • 2005-08-30 EP EP05775130A patent/EP1810554B1/en not_active Expired - Lifetime
  • 2005-08-30 WO PCT/EP2005/009332 patent/WO2006032346A1/en not_active Ceased
  • 2005-08-30 AT AT05775130T patent/ATE417492T1/de active
  • 2005-08-30 CN CN2005800315049A patent/CN101053286B/zh not_active Expired - Lifetime
  • 2005-09-13 MY MYPI20054306A patent/MY145344A/en unknown
• 2016
  • 2016-05-20 US US15/159,943 patent/US9526183B2/en not_active Expired - Lifetime

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