Flexible film semiconductor package

Abstract: A thin film package is formed using a low cost TAB interconnection on a semiconductor device (10) and sandwiching the device between thin films (12, 13) of plastic to form a sealed, thin, light weight package for the semiconductor device.

Description: This invention relates to semiconductor devices, and more particularly to a package using a thin flexible film for the packaging material. The demand for ever higher circuit board density has resulted in small size semiconductors devices having a low profile. Board space considerations have traditionally been viewed from a two dimensional perspective, and the motivation for thin packaging has been a secondary issue. However, with the electronics industry looking at thin packaging to address density issues associated with products like memory cards, smart cards, emulator cards, package thickness is a critical factor. Prior art packages include conventional packaging such as National Semiconductor's TapePak™, Tape Automated Bonding (TAB), Dual In-line Pin (DIP) packages, and Small Outline Packages (SOPs). TAB packaging uses a liquid plastic to encapsulate the semiconductor chip. Conventional prior art packages use wire bonds to connect the chip to a leadframe. TapePak TM has connections along four sides of the package. JP-A 61-27663 discloses a semiconductor package in which a semiconductor chip and its attached wiring are enclosed between two flexible films, which are attached to each other round the periphery by an adhesive agent. WO-A 90/05379, on which the preambles of claims 1 and 7 are based, discloses a similar package for use in conditions where high accelerations occur, in which the peripheral portions of the two films are clamped between the two halves of an annular clamping frame. The invention provides a thin film semiconductor device package, comprising: a semiconductor device; a plurality of leads having a first end attached to the semiconductor device at contacts, a lead part adjacent to said first ends and extending away from the semiconductor device and a second end; a first thin flexible film on one side of the semiconductor device and leads; and a second thin flexible film on the side of the semiconductor device and leads opposite said first thin flexible film; wherein said first and second thin films are bonded to each other between said lead parts, and bonded thereto to form a sealed thin film package, with said second ends of said leads extending from said thin film package; characterised in that a support ring is mounted on said lead parts and supports that one of the thin flexible films which is on the same side of the contacts in the region where the first lead ends are attached to the semiconductor device. The invention also provides a method of making a thin film packaged semiconductor device comprising the steps of: tab bond interconnecting first ends of a plurality of leads on a lead frame to contacts of a bumped semiconductor device, said leads having lead parts adjacent to said first ends and extending away from the semiconductor device and further having second lead ends; applying first and second sheets of thin flexible film material to opposite surfaces of the semiconductor device and the leads; and bonding the first and second sheets of thin flexible film material to each other and to said lead parts to form a sealed package enclosing the semiconductor device and said lead parts, whereby said second lead ends extend from said thin film package; characterised in that it includes the step of mounting a support ring on the said lead parts prior to said step of applying the sheets of thin flexible film material. The film hermetically seals the device from the environment, gives mechanical strength to the device, provides a low profile and is a low weight device. The package can be produced at low cost when compared with standard packaging techniques. The semiconductor device may be a semiconductor die or integrated circuit having "bump" contacts in either a "chip-up" or "chip-down" configuration. Offset leads may be used in conjunction with the support ring to minimize stress on the bump-lead interface. In the drawings: Figure 1 is a side view, in section, of one form of semiconductor device package; Figure 2 is a top view of the package of Figure 1; Figure 3 is a side view of a second form of package, with the semiconductor die contact side up; and Figure 4 is a side view of one form of package according to the invention with offset leads and a support ring. Figure 1 illustrates a thin film package semiconductor device. The semiconductor die 10 has a plurality of bump contacts 15 thereon. Attached to each bump contact is a lead 11. The backside 10a of the semiconductor die is covered with a thin film of material which may be, for example, Ryton, a trademarked thin film flexible material manufacture by Phillips 66. This film may be obtained in sheets of 125 µm (0.005") thickness. The generic material is Polyphenylene Sulfide Resin. The under side of the semiconductor die and the leads 11 are also covered by the plastic film. An ultrasonic bond is made between the film and leads in the regions indicated by arrows A and B. Leads may optionally be folded around the bottom film as illustrated in Figure 1. The leads, in one embodiment, were made from a palladium plated leadframe. Figure 2 is a top view of the device of Figure 1 illustrating the typical layout of leads on an integrated circuit device. Leads 11 are arrayed around the device 10 and extend out the sides of the device. The plastic film covers the device and leads, except for the ends of the leads 11a which provide external electrical contact to the integrated circuit. The number of leads and arrangement of the leads is not a critical factor, but may be arrayed around the semiconductor device depending upon the device configuration. The package is light weight, and, in one embodiment, is about 0.75mm (0.03") thick. This thin film package device is functional mechanically as well as electrically, and in most instances provide a cleaner and better sealed device than the standard epoxy molded device. No mechanical degradation has been observed during storage or solder dunk at 250° C. during lead solder coating. The process flow for the package includes the steps of tab bonding the wafer to a lead frame or leads, placing the device and leads between two sheets of film and ultrasonically sealing the film around the leads. The film seals to itself between the leads and to the leads to form a hermetic seal. Sealing of the film may be done prior to separating a plurality of devices on a continuous strip of lead frame. After sealing, the device may be symbolized and then separated into individual devices prior to testing. Figure 3 illustrates a second form of thin film package. The semiconductor device or integrated circuit 20 has a plurality of contacts 21 thereon. The leads 22 are bonded to the contacts and then angled downward to the plane of the semiconductor device. Thereafter, the top film 23 and bottom film 24 are sealed around the device, and to the leads 22. Figure 4 shows an embodiment of the thin film package according to the invention. The semiconductor device 30 is mounted with the contact side up. Leads are connected to the contacts and then bent downwardly to lie in the plane of the semiconductor device. A support ring 33 of an insulating material is mounted on the part of the lead 32b that is in the plane of the semiconductor device, and extends above the part of the lead 32a bonded to contact 31. Plastic film 34 is applied over the contacts 32 and support ring 33, and a second sheet of film 35 is placed under the semiconductor device 30. Support ring 33 relieves and minimizes stress or pressure on the junction of contact 31 and lead end 32a. The use of the support ring can also be used on devices which are wire bonded. The ring may extend completely around the device or be located just in the area of the leads/contacts.

Claims: A thin film semiconductor device package, comprising; a semiconductor device (30); a plurality of leads (32) having a first end (32a) attached to the semiconductor device (30) at contacts (31), a lead part (32b) adjacent to said first ends (32a) and extending away from the semiconductor device (30) and a second end; a first thin flexible film (34) on one side of the semiconductor device (30) and leads (32); and a second thin flexible film (35) on the side of the semiconductor device (30) and leads (32) opposite said first thin flexible film (34); wherein said first and second thin films (34,35) are bonded to each other between said lead parts (32b), and bonded thereto to form a sealed thin film package, with said second ends of said leads (32) extending from said thin film package; characterised in that a support ring (33) is mounted on said lead parts (32b) and supports that one of the thin flexible films (34) which is on the same side of the contacts (31) in the region where the first lead ends (32a) are attached to the semiconductor device (30). The thin film package according to claim 1, wherein said second lead ends (32) fold back over a portion of the film package. The thin film package according to any preceding claim, wherein said support ring (33) is of metal. The thin film package according to any preceding claim, wherein the first and second thin flexible films (34,35) are of a polyphenylene sulfide resin. The thin film package according to any preceding claim, wherein the first lead ends (32a) are connected to the semiconductor device (30) with a TAB bond. A method of making a thin film packaged semiconductor device comprising the steps of: TAB bond interconnecting first ends (32a) of a plurality of leads (32) on a lead frame to contacts (31) of a bumped semiconductor device (30), said leads (32) having lead parts (32b) adjacent to said first ends (32a) and extending away from the semiconductor device (30) and further having second lead ends; applying first and second sheets of thin flexible film material (34,35) to opposite surfaces of the semiconductor device (30) and the leads (32); and bonding the first and second sheets of thin flexible film material (34,35) to each other and to said lead parts (32b) to form a sealed package enclosing the semiconductor device (30) and said lead parts (32b), whereby said second lead ends extend from said thin film package; characterised in that it includes the step of mounting a support ring (33) on the said lead parts (32b) prior to said step of applying the sheets of thin flexible film material (34,35). The method according to claim 6, wherein said bonding is performed ultrasonically. The method according to claim 6 or 7, wherein the applying step is performed before the leads (32) are separated from a continuous leadframe strip.

Inventors: MCLELLAN NEIL R, MCLELLAN, NEIL R.
Applicants: TEXAS INSTRUMENTS INC, TEXAS INSTRUMENTS INCORPORATED
Application year: 1992
Main classification: H01L23
IPC codes: H01L23