Wafer treating method for making adhesive dies
A wafer treating method for making adhesive dies is provided. A liquid adhesive with two-stage property is coated on a surface of a wafer. Then, the wafer is pre-cured to make the liquid adhesive transform a thermo-bonding adhesive film having B-stage property which has a glass transition temperature not less than 40° C. for handling without adhesive under room temperature. After positioning the wafer, the wafer is singulated to form a plurality of dies with adhesive for die-to-die stacking, die-to-substrate or die-to-leadframe attaching.
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The present invention is generally relating to a wafer treating technique after finishing integrated circuits on a wafer, particularly to a wafer treating method for making adhesive dies.
BACKGROUND OF THE INVENTIONAfter manufacturing the integrated circuits on a semiconductor wafer, a plurality of dies are singulated from the semiconductor wafer and according to various packaging styles are attached on a proper IC substrate, or one of dies is attached one on top of the other die to form multi-chip stack. Die is attached onto a printed circuit board to form Ball Grid Array (BGA) package. Die is attached to die pad or inner leads of a lead frame to form Thin Small Outline Package (TSOP). Conventional adhesive for die-attaching is thermosetting silver liquid compound or solid polyimide adhesive tape, which is applied on base carrier (e.g., substrate, leadframe or lower die) during die-attaching.
A method for assembling multi-chip module disclosed from U.S. Pat. No. 2001/0005935 is to attach a larger die onto a substrate using a die attach machine, then a smaller die is affixed on the larger die without using a die attach machine. The adhesive attaching the larger die and the smaller die conventionally is a liquid thermosetting adhesive or solid polyimide tape. However, that is failed to disclose the procedure of coating the adhesive (firstly coated on the smaller die or on the larger die prior to die-attaching and the procedure of wire-bonding. On one hand, when a liquid thermosetting adhesive is used for die-attaching prior wire-bonding, it is difficult to pre-coat on the smaller die (upper die) and also easy to contaminate the bonding pads of the larger die (lower die) due to flowage of liquid thermosetting adhesive. On the other hand, when the liquid adhesive is printed after wire-bonding, the printing screen is unable to be placed on the larger die(or substrate) with bonding wires, so that adhesive must be applied on the larger die before wire-bonding. Thus, the limits for multi-chip packaging process are quite a lots, lead to package uneasily. Alternatively, a solid adhesive tape may also be used for die-attaching, but cost of adhesive tape is high and the adhesive tape is demanded double-sided adhesive for die-to-die, die-to-substrate or die-to-leadframe bonding. Conventionally the adhesive tape is firstly attached on a substrate (leadframe or larger die) in predetermined pattern, then a die is bonded on the adhesive tape. The dies do not have adhesive after sigulating from a wafer.
SUMMARYA first object of the present invention is to provide a wafer treating method for making adhesive dies by utilizing a liquid adhesive with two-stage property printed on a wafer. The printed adhesive with two-stage property is pre-cured to become solid without flowable and adhesive under room temperature (B-stage condition), then after singulating the wafer, a plurality of dies with B-stage adhesive will be obtained for decreasing cost of forming adhesive.
A second object of the present invention is to provide a wafer treating method for making adhesive dies by utilizing a liquid adhesive with two-stage property printed on a wafer. The adhesive with two-stage property is precured to become solid film without flowable and adhesive under room temperature (B-stage condition), then after singulating the wafer, the dies with B-stage adhesive will be obtained, so as to possess good processing characteristic for a variety of semiconductor packaging processes.
In accordance with the wafer treating method for making adhesive dies of the present invention, a semiconductor wafer having integrated circuits is provided. The wafer has a plane surface, such as an active surface or an inactive surface. A liquid adhesive with two-stage property is evenly coated on the partial or overall surface of the wafer by means of screen printing, stencil printing or spin coating. It is desirable to coat the liquid adhesive with two-stage property on the partial surface of the wafer without covering the cutting paths or bonding pads of the wafer. Next, the wafer is pre-cured to make the adhesive with two-stage property become a wafer-level thermo-bonding adhesive film with B-stage property, that is, being solid without flowable and adhesive under room temperature. Usually the pre-cured time is about 1 hour around 125° C. Meanwhile, the B-stage solid film has thermosetting property and adhesion of thermal bonding, also has a glass transition temperature (Tg) more than 40° C. for operation of positioning the wafer, sucking the dies utilizing a die binder and transportation after singulating the dies from the wafer. Thus the dies with wafer-level thermo-bonding adhesive film are provided to affix to a substrate, another die, a printed circuit board, a ceramic circuit board or a lead frame without extra adhesive. Therefore, the dies with wafer-level thermo-bonding adhesive film are able to be efficiently, broadly used in die-to-die stack or die-to-substrate attach for various packages at low cost.
Additionally, the present invention is directed to a chip package comprising a carrier, a first chip, a first adhesive layer and a molding compound. The first chip is disposed on the carrier and electrically connected with the carrier. The first adhesive layer is disposed between the carrier and the first chip, wherein an area of the first adhesive layer is not larger than an area of the first chip. The molding compound is disposed on the carrier to cover the first chip.
In accordance with the chip package of the present invention, the chip package further comprises a plurality of first bonding wires, which are electrically connected with the carrier and the first chip. The first adhesive layer can be an adhesive film, wherein the adhesive film can be an adhesive film having B-stage property.
In accordance with the chip package of the present invention, wherein the carrier is a package substrate or a lead frame.
In accordance with the chip package of the present invention, the chip package further comprises a second adhesive layer and a second chip, wherein the second adhesive layer is disposed on the first chip and the second chip is disposed on the second adhesive layer. And wherein an area of the second adhesive layer is not larger than an area of the second chip and the second chip is electrically connected with the carrier.
In accordance with the chip package of the present invention, the chip package further comprises a plurality of second bonding wires, which are electrically connected with the carrier and the second chip.
In accordance with the chip package of the present invention, wherein the second bonding wires and the second chip are covered with the molding compound. In accordance with the chip package of the present invention, wherein the second adhesive layer is disposed between an inactive surface of the second chip and an active surface of the first chip.
In accordance with the chip package of the present invention, wherein the second adhesive layer can be an adhesive film.
In accordance with the chip package of the present invention, wherein the second adhesive layer can be an adhesive film having B-stage property.
In addition, the present invention is directed to a chip package comprising a carrier, a first chip, a second chip, a second adhesive layer and a molding compound. The first chip is disposed on the carrier and electrically connected with the carrier. The second chip is disposed on the first chip and electrically connected with the carrier. The second adhesive layer is disposed between the first chip and the second chip, wherein an area of the second adhesive layer is not larger than an area of the second chip. The molding compound is disposed on the carrier to cover the first chip, the second chip, and the second adhesive layer.
In accordance with the chip package of the present invention, the chip package further comprises a plurality of first bonding wires, which are electrically connected with the carrier and the first chip.
In accordance with the chip package of the present invention, the chip package further comprises a plurality of second bonding wires, which are electrically connected with the carrier and the second chip.
In accordance with the chip package of the present invention, wherein the second adhesive layer can be an adhesive film.
In accordance with the chip package of the present invention, wherein the second adhesive layer can be an adhesive film having B-stage property.
In accordance with the chip package of the present invention, the chip package further comprises a first adhesive layer, which is disposed between the carrier and the first chip. In addition, the first adhesive layer can be an adhesive film.
In accordance with the chip package of the present invention, wherein the first adhesive layer can be an adhesive film having B-stage property.
In accordance with the chip package of the present invention, wherein the carrier is a package substrate or a lead frame.
In accordance with the chip package of the present invention, wherein the second adhesive layer is disposed between an inactive surface of the second chip and an active surface of the first chip.
Referring to the drawings attached, the present invention will be described by means of the embodiments below.
As shown in
As illustrated in
Next, the step of “pre-curing the wafer” 13 is executed as shown in
Next, the step of “positioning the wafer” 14 is executed as shown in
In order to understand the present invention is not limited to the printing surface of wafer, the second embodiment is presented. As shown in
Then, as shown in
Moreover, in the third embodiment of the present invention, the process steps are the same as those illustrated in the second embodiment shown in
The above description of embodiments of this invention is intended to be illustrative and not limiting. Other embodiments of this invention will be obvious to those skilled in the art in view of the above disclosure.
Claims
1. A wafer treating method for making adhesive dies comprising the steps of:
- providing a wafer having a surface;
- coating a liquid adhesive with two-stage property on the surface of the wafer, wherein the surface of the wafer is partially coated with the liquid adhesive;
- pre-curing the liquid adhesive so that the liquid adhesive transforms into a wafer-level thermo-bonding adhesive film having B-stage property;
- providing a positioning tape in contact with the wafer-level thermo-bonding adhesive film for positioning the wafer; and
- singulating the wafer on the positioning tape so as to form a plurality of dies with the wafer-level thermo-bonding adhesive film.
2. The wafer treating method for making adhesive dies in accordance with claim 1, wherein the liquid adhesive is formed by screen printing, stencil printing or spin coating.
3. The wafer treating methods for making adhesive dies in accordance with claim 1, wherein the surface of the wafer is an active surface of the wafer.
4. The wafer treating method for making adhesive dies in accordance with claim 1, wherein the surface of the wafer is an inactive surface of the wafer.
5. The wafer treating method for making adhesive dies in accordance with claim 1, wherein the surface of the wafer is partially coated with the liquid adhesive.
6. The wafer treating method for making adhesive dies in accordance with claim 5 1, wherein the wafer has cutting paths and bonding pads and wherein the surface is coated with the liquid adhesive without covering the cutting path and the bonding pads of the wafer.
7. The wafer treating method for making adhesive dies in accordance with claim 1, wherein the entire surface of the wafer is coated with liquid adhesive.
8. The wafer treating method for making adhesive dies in accordance with claim 1, wherein the wafer-level thermo-bonding adhesive film has a glass transition temperature (Tg) not less than 40° C.
9. The wafer treating method for making adhesive dies in accordance with claim 1, wherein the wafer-level thermo-bonding adhesive film has a thickness between 3˜8 mil for die-to-die stacking.
10. The wafer treating method for making adhesive dies in accordance with claim 1, wherein the wafer-level thermo-bonding adhesive film has a thickness between 5˜6 mil for die-to-die stacking.
11. The wafer treating method for making adhesive dies in accordance with claim 1, wherein the wafer-level thermo-bonding adhesive film has a thickness between 1˜3 mil for die-to-substrate or die-to-leadframe attaching.
12. A wafer treating method for making adhesive dies comprising the steps of:
- providing a wafer having an active surface upwardly, wherein a plurality of bonding pads are formed on the active surface, there are a plurality of cutting paths at the wafer to define dies;
- coating a liquid adhesive on the partially active surface of the wafer, wherein the liquid adhesive exposes the bonding pads;
- pre-curing the liquid adhesive so that the liquid adhesive transforms into a wafer-level thermo-bonding adhesive film having B-stage property; and
- singulating the wafer along the cutting path so as to form a plurality of dies with the wafer-level thermo-bonding adhesive film.
13. The wafer treating method for making adhesive dies in accordance with claim 12, wherein the liquid adhesive is formed by screen printing or stencil printing method.
14. The wafer treating method for making adhesive dies accordance with claim 12, wherein the wafer-level thermo-bonding adhesive film has a glass transition temperature (Tg) not less than 40° C.
15. The wafer treating method for making adhesive dies in accordance with claim 12, wherein the wafer-level thermo-bonding adhesive film has a thickness between 1˜3 mil for die-to-leadframe attaching.
16. The wafer treating method for making adhesive dies in accordance with claim 12, wherein the coating step of a liquid adhesive, the liquid adhesive exposes the cutting paths.
5635010 | June 3, 1997 | Pepe et al. |
6689638 | February 10, 2004 | Lin et al. |
6943061 | September 13, 2005 | Sirinorakul et al. |
20010005935 | July 5, 2001 | Tandy |
58-196031 | November 1983 | JP |
6-302629 | October 1994 | JP |
457654 | October 2001 | TW |
Type: Grant
Filed: Mar 7, 2006
Date of Patent: May 10, 2011
Assignees: ChipMOS Technologies (Bermuda) (Hamilton), ChipMOS Technologies Inc. (Hsinchu)
Inventors: Chun-Hung Lin (Tainan), Jesse Huang (Kaohsiung), Kuang-Hui Chen (Kaohsiung), Shih-Wen Chou (Tainan)
Primary Examiner: Timothy H Meeks
Assistant Examiner: Cachet I Sellman
Attorney: J.C. Patents
Application Number: 11/371,307
International Classification: B05D 5/10 (20060101); B05D 3/12 (20060101); H01L 21/00 (20060101);