A flip chip process based on electroplated solder bumps

Jaakko Salonen, Jorma Salmi

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)

Abstract

Compared to wire bonding and TAB, flip chip technology using solder joints offers the highest pin count and packaging density and superior electrical performance. The chips are mounted upside down on the substrate, which can be made of silicon, ceramic, glass or - in some cases - even PCB. The extra processing steps required for chips are the deposition of a suitable thin film metal layer(s) on the standard Al pad and the formation of bumps. Also, the development of new fine line substrate technologies is required to utilize the full potential of the technology. In our bumping process, bump deposition is done by electroplating, which was chosen for its simplicity and economy.

Sputter deposited molybdenum and copper are used as thin film layers between the aluminum pads and the solder bumps. A reason for this choice is that the metals can be selectively etched after bumping using the bumps as a mask, thus circumventing the need for a separate mask for etching the thin film metals. The bumps are electroplated from a binary Pb-Sn bath using a thick liquid photoresist.

An extensively modified commercial flip chip bonder is used for alignment and bonding. Heat assisted tack bonding is used to attach the chips to the substrate, and final reflow joining is done without flux in a vacuum furnace.
Original languageEnglish
Pages (from-to)230-233
Number of pages4
JournalPhysica Scripta
Volume1994
Issue numberT54
DOIs
Publication statusPublished - 1994
MoE publication typeA1 Journal article-refereed

Fingerprint

Flip chip
solders
Thin Films
Chip
Metals
chips
Substrate
Mask
Glass-ceramics
Solder Joint
Photoresist
Furnace
Packaging
Etching
Joining
Copper
masks
Aluminum
thin films
metals

Cite this

Salonen, Jaakko ; Salmi, Jorma. / A flip chip process based on electroplated solder bumps. In: Physica Scripta. 1994 ; Vol. 1994, No. T54. pp. 230-233.
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title = "A flip chip process based on electroplated solder bumps",
abstract = "Compared to wire bonding and TAB, flip chip technology using solder joints offers the highest pin count and packaging density and superior electrical performance. The chips are mounted upside down on the substrate, which can be made of silicon, ceramic, glass or - in some cases - even PCB. The extra processing steps required for chips are the deposition of a suitable thin film metal layer(s) on the standard Al pad and the formation of bumps. Also, the development of new fine line substrate technologies is required to utilize the full potential of the technology. In our bumping process, bump deposition is done by electroplating, which was chosen for its simplicity and economy.Sputter deposited molybdenum and copper are used as thin film layers between the aluminum pads and the solder bumps. A reason for this choice is that the metals can be selectively etched after bumping using the bumps as a mask, thus circumventing the need for a separate mask for etching the thin film metals. The bumps are electroplated from a binary Pb-Sn bath using a thick liquid photoresist.An extensively modified commercial flip chip bonder is used for alignment and bonding. Heat assisted tack bonding is used to attach the chips to the substrate, and final reflow joining is done without flux in a vacuum furnace.",
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A flip chip process based on electroplated solder bumps. / Salonen, Jaakko; Salmi, Jorma.

In: Physica Scripta, Vol. 1994, No. T54, 1994, p. 230-233.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - A flip chip process based on electroplated solder bumps

AU - Salonen, Jaakko

AU - Salmi, Jorma

PY - 1994

Y1 - 1994

N2 - Compared to wire bonding and TAB, flip chip technology using solder joints offers the highest pin count and packaging density and superior electrical performance. The chips are mounted upside down on the substrate, which can be made of silicon, ceramic, glass or - in some cases - even PCB. The extra processing steps required for chips are the deposition of a suitable thin film metal layer(s) on the standard Al pad and the formation of bumps. Also, the development of new fine line substrate technologies is required to utilize the full potential of the technology. In our bumping process, bump deposition is done by electroplating, which was chosen for its simplicity and economy.Sputter deposited molybdenum and copper are used as thin film layers between the aluminum pads and the solder bumps. A reason for this choice is that the metals can be selectively etched after bumping using the bumps as a mask, thus circumventing the need for a separate mask for etching the thin film metals. The bumps are electroplated from a binary Pb-Sn bath using a thick liquid photoresist.An extensively modified commercial flip chip bonder is used for alignment and bonding. Heat assisted tack bonding is used to attach the chips to the substrate, and final reflow joining is done without flux in a vacuum furnace.

AB - Compared to wire bonding and TAB, flip chip technology using solder joints offers the highest pin count and packaging density and superior electrical performance. The chips are mounted upside down on the substrate, which can be made of silicon, ceramic, glass or - in some cases - even PCB. The extra processing steps required for chips are the deposition of a suitable thin film metal layer(s) on the standard Al pad and the formation of bumps. Also, the development of new fine line substrate technologies is required to utilize the full potential of the technology. In our bumping process, bump deposition is done by electroplating, which was chosen for its simplicity and economy.Sputter deposited molybdenum and copper are used as thin film layers between the aluminum pads and the solder bumps. A reason for this choice is that the metals can be selectively etched after bumping using the bumps as a mask, thus circumventing the need for a separate mask for etching the thin film metals. The bumps are electroplated from a binary Pb-Sn bath using a thick liquid photoresist.An extensively modified commercial flip chip bonder is used for alignment and bonding. Heat assisted tack bonding is used to attach the chips to the substrate, and final reflow joining is done without flux in a vacuum furnace.

U2 - 10.1088/0031-8949/1994/T54/056

DO - 10.1088/0031-8949/1994/T54/056

M3 - Article

VL - 1994

SP - 230

EP - 233

JO - Physica Scripta

JF - Physica Scripta

SN - 0031-8949

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