IN PACKAGE ESD PROTECTIONS OF IC USING A THIN FILM POLYMER

• US 20080278873A1
• Filed: 03/17/2008
• Published: 11/13/2008
• Est. Priority Date: 05/10/2007
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Duvvury, Charvaka, Messina, Nathalie, Wachtler, Kurt P., Leduc, Yves
• Granted Patent: US 7,872,841 B2
• Time in Patent Office: Days
• US Class Current: 361/56
• CPC Class Codes: H01L 2224/0554 External layer
• CPC Class Codes: H01L 2224/0555 Shape
• CPC Class Codes: H01L 2224/0556 Disposition
• CPC Class Codes: H01L 2224/0557 the external layer being disposed on a via connection of the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/05571 the external layer being disposed in a recess of the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/056 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 23/60 Protection against electrostatic charges or discharges, e.g. Faraday shields
• CPC Class Codes: H01L 23/62 Protection against overvoltage, e.g. fuses, shunts
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/13034 Silicon Controlled Rectifier [SCR]
• CPC Class Codes: H01L 2924/15311 being a ball array, e.g. BGA
• CPC Class Codes: H05K 1/0259 Electrostatic discharge [ESD] protection
• CPC Class Codes: H05K 2201/0738 Use of voltage responsive materials, e.g. voltage switchable dielectric or varistor materials
• CPC Class Codes: Y10T 29/49105 Switch making

Abstract

A packaged semiconductor device (200) with a substrate (220) having, sandwiched in an insulator (221), a flat sheet-like sieve member (240) made of a non-linear material switching from insulator to conductor mode at a preset voltage. Both member surfaces are free of indentations; the member is perforated by through-holes, which are grouped into a first set (241) and a second set (242). Metal traces (251) over one member surface are positioned across the first set through-holes (241); each trace is connected to a terminal on the substrate top and, through the hole, to a terminal on the substrate bottom. Analogous for metal traces (252) over the opposite member surface and second set through-holes (242). Traces (252) overlap with a portion of traces (252) to form the locations for the conductivity switches, creating local ultra-low resistance bypasses to ground for discharging overstress events.

Claims

1. A device comprising:

an electronic component having first electrodes for electrical signal and power, and second electrodes for electrical ground;

a substrate, onto which the component is assembled, having built-in local protection shortcuts for the first electrodes operable to bypass electrical overcharge events directly to ground, the substrate including;

an insulator material having a top surface with a first set and a third set of terminals, and a bottom surface with a second set and a fourth set of terminals;

a flat sheet-like sieve member sandwiched in the insulator, the sieve member made of a non-linear material that switches from insulator to conductor mode at a preset voltage, the member perforated with a first set and a second set of through-holes and otherwise being free of indentations on its surfaces, and;

first metal traces over the first surface, each first trace positioned covering a first set through-hole and having a conductive connection to a third set terminal and a conductive connection to a second set terminal;

second metal traces on the second surface, each second trace covering a second set through-hole and overlapping a first trace, the overlap areas constituting a conductivity switch, and the second metal traces further having a conductive connection to a fourth set terminal and a conductive connection to a first set terminal; and

the first and second electrodes connected to the first and third set terminals so that each first electrode is connected to a switch built into the substrate.

2. The device of claim 1 further having the second set terminals connected to external electrical signal or power and the fourth set terminals connected to external electrical ground.

3. The device of claim 1 wherein the sheet-like sieve member has a thickness between about 3 and 10 μ

m, which controls the voltage for the onset of the conductive mode from the insulating mode of the non-linear material.

4. The device of claim 1 wherein the electronic component is an integrated circuit chip.

5. The device of claim 1 wherein the insulator material of the substrate is made of an epoxy-based compound.

6. The device of claim 1 wherein the terminals and metal traces are made of copper.

7. The device of claim 1 wherein the electrodes are connected to the terminals by solder bodies.

8. The device of claim 1 wherein the electrodes are connected to the terminals by bonding wires.

9. The device of claim 8 further having an encapsulation compound covering the component and the bonding wires.

10. The device of claim 1 wherein the switches have an electrical resistance between about 2 and 20 mΩ

.

11. A method for fabricating a semiconductor device, comprising the steps of:

providing a tape having a length and a width including a sheet of non-linear material sandwiched between a first and a second metal layer,

the sheet being capable of switching from insulator to conductor mode at a preset voltage, extending over the entire tape length and width and being without indentations or grooves on its surfaces;

patterning the first metal layer to create first metal traces separated by first gaps;

patterning the second metal layer to create second metal traces separated by second gaps and overlapping portions of the first traces;

providing a first insulator foil laminated with a third metal layer;

placing the first foil on the first traces, the third metal layer facing outwardly;

providing a second insulator foil laminated with a fourth metal layer;

placing the second foil on the second traces, the fourth metal layer facing outwardly;

laminating the insulators of each foil unto the respective traces and filling the gaps between the traces with insulating material, thereby creating the tape-like substrate having sites for a series of repetitive devices;

opening a first set of through-holes, aligned with the first gaps, extending through the third metal layer, the first insulator foil, the insulator-filled gaps, and the sheet of non-linear material, thereby perforating the sheet with a first set of through-holes terminating at the second metal traces;

opening a second set of through-holes, aligned with the second gaps, extending through the fourth metal layer, the second insulator foil, the insulator-filled gaps, and the sheet of non-linear material, thereby perforating the sheet with a second set of through-holes terminating at the first metal traces;

opening a third set of through-holes extending through the third metal layer and first insulator foil, terminating at the first metal traces;

opening a fourth set of through-holes extending through the fourth metal layer and second insulator foil, terminating at the second metal traces;

depositing metal to fill the through-holes and to add a continuous fifth metal layer on top of the third metal layer and a continuous sixth metal layer on top of the fourth metal layer;

patterning the fifth and third metal layers to create terminals connected to a respective metal-filled through-hole, wherein terminals connected to a first set through-hole represent a first set, and terminals connected to a second set through-hole represent a second set;

patterning the sixth and fourth metal layers to create terminals connected to a respective metal-filled through-hole, wherein terminals connected to a third set through-hole represent a third set, and terminals connected to a fourth set through-hole represent a fourth set;

selecting certain second traces and the respective fourth and first set terminals for connection to electrical ground;

selecting certain second traces, the first traces, and the respective terminals of the fourth, first, second, and third sets for connection to electrical signal or power;

providing a plurality of electronic components having first electrodes for electrical signal and power, and second electrodes for electrical ground;

connecting the first electrodes to the terminals of the respective substrate site for signal and power;

connecting the second electrodes of the component to the terminals of the respective substrate site for ground;

repeating the connecting steps for each component to assemble the component to the respective substrate site; and

singulating the tape with the assembled components into discrete devices.

12. The method of claim 11 further including the steps of connecting the fourth set terminals selected for ground to external ground, and connecting the fourth and second set terminals selected for signal and power to external signal and power supplies.

13. The method of claim 11 wherein the non-linear material comprises an insulating polymer compound embedded with nanometer-size conducting particles, the material switching from insulator to conductor mode at a preset voltage.

14. The method of claim 11 wherein all metal layers, and the metal filling the through-holes are copper.

15. The method of claim 11 wherein the first and second insulator foils are made of an epoxy-based compound.

16. The method of claim 11 further including, after the step of depositing metal, the steps of:

preparing the fifth metal sheet to facilitate the process of attaching wire bonds or the process of attaching flip-chip bumps; and

preparing the sixth metal sheet to facilitate the process of attaching solder bodies.

17. The method of claim 11 wherein the step of connecting the electrodes to the terminals employs a wire bonding technique.

18. The method of claim 17 further including the step of covering the component and the wire bonds with an encapsulation compound.

19. The method of claim 11 wherein the step of connecting the electrodes to the terminals employs a flip-chip technique using metal bumps.

20. The method of claim 11 further including the step of attaching solder balls to the terminals of the third and fourth sets.