WO2015096123A1

WO2015096123A1 - A process for die bonding in electronic products

Info

Publication number: WO2015096123A1
Application number: PCT/CN2013/090682
Authority: WO
Inventors: Changjing CHEN; Jie Shen; Wangsheng FANG; Jing Zhou; Xuan Hong; Qizhuo Zhuo
Original assignee: Ablestik Shanghai Ltd; Henkel Corp
Current assignee: Ablestik Shanghai Ltd; Henkel Corp
Priority date: 2013-12-27
Filing date: 2013-12-27
Publication date: 2015-07-02
Anticipated expiration: 2016-06-27
Also published as: JP6415574B2; JP2017502521A; CN106463479A; KR20160103030A

Abstract

A process for die bonding in electronic products, such as in memory card, including a dam-fill process and a printing process is provided. The dam-fill process utilizes a dam material and a fill material, and the printing process utilizes a printed steel stencil and a paste material.

Description

A PROCESS FOR DIE BONDING IN ELECTRONIC PRODUCTS

Technical Field

The present invention relates to a process for die bonding in electronic products, in particular, relates to a process for die bonding in memory card such as embedded Multi Media Card.

Background Technology

Electronic products such as memory card are experiencing high turnovers, take an embedded Multi Media Card (briefly as "eMMC") for example, eMMC is extended from Multi Media Card for embedded memory which is one of the main specifications for a smooth pathway to elegant and advanced mobile designs with a short time to market. The current trend for developing eMMC is that the controller die moves to the substrate and under the memory die for purpose of space saving, minimization and multi-functionalisation, which means, the mother memory die needs to be attached to the top of the controller die or other similar component in advance.

Existing solution for this change is to use FOD (film over die) to attach the memory die. There is already commercial product for this kind of FOD material. However, if the controller die and the memory die become bigger, which is one of the trends for memory device, there will be serious warpage issue since both the substrate and the memory die are very thin and can not suffer high stress. Meanwhile, the cost for FOD is very high which is not acceptable for many memory device players. Developments were attempted. Alternative solution 1 is to use spacer die to bond the bottom memory die to the substrate and then followed by standard stack die bonding, wire bonding and molding. This solution is cheaper than FOD, but the risk of die crack during wire bonding is high and the yield is rather low. Alternative solution 2 is to use standard molding process to mold the controller die and/or other similar component then followed with standard stack die bonding, wire bonding and molding. In both of the above alternative solutions, usually, an extra film material is needed to attach the memory die which increases the total material cost, and usually the adhesion between the film and the molding compound is very limited. Thus, both of the above solutions have been demonstrated not so positive because of die crack issue, delamination, high warpage or low yield.

Dam and fill material is known in the adhesive area and it has also been applied in electronic product packaging for a while. In the prior art, however, the dam and fill material is only used for packaging so as to protect the components therein. There is no attempt so far to develop a dam and fill material which can not only be used for packaging but also can be further used to directly bond components in the electronic products, such as die components.

Summary of the invention

In view of the current technical trend for die packaging in the electronic products, especially in the memory card, one object of the present invention is to provide an easy and low cost process for die bonding and to solve the problems in the existing solutions, such as warpage, low yield and high cost. Surprisingly, the present inventors found that a process by utilizing a dam material and a fill material (briefly as the D-F process) and a printing process by utilizing a printed steel stencil with a set of particular apertures and a paste material (briefly as the printing process) can solve the warpage and die crack problems which often occur while using FOD or other alternative solutions in die bonding. Both of the processes achieve good adhesion and low stress/strip warpage in die bonding, and they are easy and low cost processes which are suitable for big controller die and ultra thin memory die. In some cases, no additional film or die attachment material is needed for attaching the memory die.

In one aspect of the present invention, the D-F process is provided, and said D-F process for die bonding comprises the following steps:

1) a dam material is dispensed around one or more first die on a substrate;

2) a fill material is dispensed into the region defined by the dam material, and optionally the substrate is heated in the meantime;

3) optionally, the fill material is partially cured;

4) a second die is bonded onto the fill material; and

5) the dam and fill material is completely cured.

In the D-F process, the dam material is similar to the standard DA (Die Attachment) paste but has relatively high viscosity and high T.I. which helps to keep its original shape after dispensing, while the fill material has very low viscosity and very good flow-ability so that it can easily flow along substrate, wire, die and other components and get full coverage in a very short time after dispensing.

In another aspect of the present invention, the printing process is provided, and said printing process comprises the following steps:

1) a printed steel stencil with a set of particular apertures is used to cover one or more first die on a substrate;

2) a paste material is printed into the apertures so as to cover said one or more first die;

3) optionally, the paste material is partially cured; 4) a second die is bonded onto the paste material; and

5) the paste material is fully cured.

The printing process is even easier and gives very high UPH (unit per hour) than the D-F process.

The present invention also provides a memory card, such as embedded Multi Media Card prepared from the D-F process or the printing process.

Description of the Drawings

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

Figure la and lb are schematic drawings showing the traditional configuration of the eMMC package,

Figure 2 is a schematic drawing showing the modified configuration of the eMMC package,

Figure 3 is a flow chart showing the steps in the D-F process, and

Figure 4 is a flow chart showing the steps in the printing process.

Detailed description of the Invention

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. Except where expressly noted, trademarks are shown in upper case. Unless stated otherwise, all percentages, parts, ratios, etc., are by weight.

When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

When the term "about" is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to.

As used herein, the terms "comprises", "comprising", "includes", "including," "has", "having", "contains" or "containing", or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not to an exclusive "or". For example, a condition A "or" B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Also, the indefinite articles "a" and "an" preceding an element or component of the invention are intended to be nonrestrictive regarding the number of instances (i.e. occurrences) of the element or component. Therefore "a" or "an" should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

The materials, methods, and examples herein are illustrative only and, except as specifically stated, are not intended to be limiting. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

The invention is described in detail hereinunder. the D-F process

In the D-F process, the dam material comprises basic resin, epoxy hardener, curing agent, filler, and other additives, wherein the basic resin is one or more selected from the group consisting of Epoxy Resin, BMI Resin and Vinyl Resin.

Epoxy Resin, also known as polyepoxide, is a class of reactive prepolymer and polymer which contains epoxide groups, such as Bisphenol-A epoxy, CTBN modified epoxy, etc. Epoxy Resin may be reacted (cross-linked) either with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols, and thiols. These co-reactants are often referred to as epoxy hardener.

BMI Resin, short for bismaleimide resin, is a class of compounds with two maleimide groups connected by the nitrogen atoms via a linker (said link for example being an alkylene group). Poly-(oxytetra-methylene)-di-(2-maleimidoacetate) is such kind of BMI resin.

Vinyl Resin is a kind of monomer, prepolymer or polymer which contains vinyl groups, such as Phenoxy ethyl acrylate and poly butadiene.

Epoxy hardener, as explained for Epoxy Resin above, includes a wide range of co-reactants reacted with Epoxy Resin, including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols, and thiols.

The same as epoxy hardener, curing agent is an ingredient that helps harden or cure another substrate. For example, peroxide is usually the curing agent for Vinyl Resin, as well as for BMI Resin.

Filler is particulate substance added to a matrix material, usually to improve its properties, such as viscosity, T.I., inner strength and coefficient of thermal expansion. Silica and alumina are typical fillers.

Besides the basic resin, epoxy hardener, curing agent and filler, some other chemicals are added into the formula to improve the adhesion strength, to adjust the T.I., to improve the compatibility and so on. These chemicals are sorted as additives, e.g. the silane.

There is no special restriction to these components in the dam material and they can be any common and conventional components chosen by a person skilled in the art as long as the dam material has relatively high viscosity and high T.I. so as to help keeping its original shape after dispensing. For example, the basic resin can comprise Epoxy Resin, BMI Resin and Vinyl Resin at the same time, the epoxy hardener can cure Epoxy Resin, the curing agent can cure BMI and Vinyl Resins, and the filler is used for adjusting T.I., improving the strength etc. Also, the additives are included to increase the adhesion, flow-ability and adjust T.I. Especially, the dam material comprises 0-20%, preferably 4-8%> of Epoxy Resin, 0-30%>, preferably 20-28% of BMI Resin, 0-30%, preferably 14-20% of Vinyl Resin, 0-5%, preferably 0.2-1.0%) of epoxy hardener, 0-5%>, preferably 0.2-1.2%> of curing agent, 30-80%), preferably 40-60%) of filler and 0-5%>, preferably 0.5-2.0%) of other additives, based on the total weight of the dam material and the sum of each component being 100%.

In the D-F process, the viscosity of the dam material at 5 rpm at 25 ^°C is in the range of 5,000-500,000 mPa-s, preferably in the range of 40,000-50,000 mPa-s, the thixotropic index (T.I.) of the dam material is more than 1.0, preferably from 4.0-6.0.

Further, in the D-F process, the fill material comprises basic resin, epoxy hardener, curing agent, filler, and other additives, wherein the basic resin is one or more selected from the group consisting of Epoxy Resin, BMI Resin and Vinyl Resin. The definitions for these components are the same with those provided for the dam material. For examples, Epoxy Resin can be selected from Bisphenol-A Epoxy and Bisphenol-F Epoxy.

There is no special restriction to these components in the fill material and they can be any common and conventional components chosen by a person skilled in the art as long as the fill material has very low viscosity and very good flow-ability so that it can easily flow along substrate, wire, die and other components and get full coverage in a very short time after dispensing. For example, the basic resin can comprise Epoxy Resin, BMI resin and Vinyl Resins at the same time, the epoxy hardener can cure Epoxy Resin, the curing agent can cure BMI resin and Vinyl Resin, and the filler is used for adjusting T.I., improving the strength etc. Also, the additives are included to increase the adhesion, anti-bleed and adjust T.I. Especially, the fill material comprises 0-30%, preferably 8-16% of Epoxy Resin, 0-40%, preferably 25-30% of BMI Resin, 0-40%, preferably 6-16% of Vinyl Resin, 0-5%, preferably 0.2-1.2% of epoxy hardener, 0-5%>, preferably 0.6-1.0%) of curing agent, 0-70%>, preferably 45-50%) of filler and 0-5%>, preferably 0.8-1.5%) of other additives, based on the total weight of the fill material and the sum of each component being 100%.

Preferably, the viscosity of the fill material at 25 ^°C is in the range of less than 50,000 mPa-s, more preferably less than 10,000 mPa-s, the T.I of the fill material is less than 3.0, more preferably less than 1.5.

In an embodiment of the D-F process, the first die is a controller die and the second die is a memory die. The terms "first die" and "second die" within the meaning of the present invention shall be construed in a way that they are used to differentiate dies used in different steps, there is no specific limit to the types of the "first die" and the "second die", which comprises common types of dies used in a memory card, as well as passive components such as capacitance, resistance, inductance, and other functional dies, such as RF-related dies, security dies, sensor dies, power dies, digital signal processor dies, logic dies, transceiver dies and so on.

In a preferable embodiment of the D-F process, in step 2), the substrate is heated slightly so as to improve the flow and coverage of the fill material.

In a preferable embodiment of the D-F process, the cure is performed via UV or heating.

In a preferable embodiment of the D-F process, the region defined by the dam material has an area of about 70% -100% of the area of the second die, preferably 90%.

The printing process

In one embodiment of the printing process, the paste material comprises basic resin, epoxy hardener, curing agent, filler, and other additives, wherein the basic resin is one or more selected from the group consisting of Epoxy Resin, BMI Resin and Vinyl Resin. The definitions for these components are the same with those provided for the dam material. For examples, Epoxy Resin can be selected from Bisphenol-A Epoxy and Bisphenol-F Epoxy.

There is no special restriction to these components in the paste material and they can be any common and conventional components chosen by a person skilled in the art as long as the paste material has a viscosity in the range of 1,000-500,000 mPa-s at 25 ^°C , and T.I. of more than 1.0. For example, the basic resin can comprise Epoxy Resin, BMI Resin and Vinyl Resin at the same time, the epoxy hardener can cure epoxy resin, the curing agent can cure BMI and Vinyl resins, and the filler is used for adjusting T.I., improving the strength etc. Also, the additives are included to increase the adhesion and adjust T.I. etc. Especially, the paste material comprises 0-30%, preferably 5-10% of Epoxy Resin, 0-30%>, preferably 20-30%) of BMI Resin, 0-30%, preferably 15-28% of Vinyl Resin, 0-6%, preferably 0.2-1.5% of epoxy hardener, 0-5%>, preferably 0.2-1.0%) of curing agent, 30-70%), preferably 30-55%) of filler, and 0-5%), preferably 1.0-1.5%) of other additives, based on the total weight of the paste material and the sum of each component being 100%.

In the printing process, the viscosity of the paste material at 25 ^°C is in the range of 1,000-500,000 mPa-s, preferably in the range of 15,000-50,000 mPa-s, the T.I. of the paste material is more than 1.0, preferably from 1.5-3.0.

In an embodiment of the printing process, prior to step 1), a dam material can be optionally dispensed around said one or more first die on a substrate. Said dam material is the same with the dam material applied in the D-F process, and a discussion for the dam material is omitted herein.

In an embodiment of the printing process, the first die is a controller die and the second die is a memory die. The terms "first die" and "second die" within the meaning of the present invention shall be construed in a way that they are used to differentiate dies used in different steps, there is no specific limit to the types of the "first die" and the "second die", which comprises common types of dies used in a memory card, as well as passive components such as capacitance, resistance, inductance, and other functional dies, such as RF-related dies, security dies, sensor dies, power dies, digital signal processor dies, logic dies, transceiver dies and so on.

In an embodiment of the printing process, the cure is performed via UV or heating. Examples

The present invention will be illustrated in more detail accompanying with the following examples and the drawings.

I. Test method

Viscosity

The viscosity for the dam material, the fill material, and the paste material was measured by Brookfield Model HBDV-III (CP-51), supplied by Brookfield, at 5 rpm at 25 ^°C .

T.I. (Thixotropic index)

T.I. value for the dam material, the fill material and the paste material was calculated based on the following equation:

TI = (viscosity at 0.5 rpm) / (viscosity at 5.0 rpm)

The viscosity at 0.5 rpm and at 5.0 rpm is measured by Brookfield Model HBDV-III (CP-51), supplied by Brookfield Corporation, at 25 ^°C .

DSC (Differential Scanning Calorimeter) Measurement

Curing reaction profiles of the dam material, the fill material and the paste material were obtained by determining the heat flow through the materials as a function of temperature using a Perkin-Elmer Differential Scanning Calorimeter (DSC-7), supplied by Perkin-Elmer Inc. The temperature range was from 25 ^°C to 300 ^°C at a temperature raising rate of 10^°C /min.

Die shear strength

Definition: The value of tangential force required to break the bond between the die and the substrate in a uniform direction.

The die shear tester was Dage 4000, supplied by Dage.

BLT (Bond Line Thickness)

Definition: the thickness of an adhesive layer and measured by Nikon microscope MM-40 (Supplied by Nikon Corporation).

Strip Warpage (reported in μιη)

Strip Warpage was measured by placing an object on a horizontal plane, determining the difference between the highest point and the lowest point of the warpage by Cyber scan laser profilometer VANTAGE -2 (Supplied by Cyber Technologies).

II. Materials

SR 495B: Isodecyl Acrylate monomer, supplied by Sartomer

SR 610: Poly(ethylene glycol) diacrylate, supplied by Sartomer

RAS-1 : Functionalized Epoxy Resin, supplied by Henkel

EPON Resin 58005 : CTBN modified Epoxy Resin, supplied by Hexion Art Resin UN 9200: Polyurethane modified acrylate, supplied by Negami Chemical SRM-1 : BMI Resin, supplied by Henkel

Ricon 131 MA10: Maleic anhydride butadiene copolymer, supplied by Sartomer Catalyst 313 B: N,N'-(4-Methyl- 1 ,3-phenylene)di(pyrrolidine- 1 -carboxamide), epoxy hardener, supplied by Henkel

Dicumyl peroxide: Peroxide, supplied by Akzo Nobel

Z 6040: 3(-glycidoxypropyl)trimethoxysilane, supplied by Dow

Corning

Z 6030: Trimethoxysilylpropyl methacrylate, supplied by Dow Corning BYK-333: Silicon based polymer, Supplied by BYK Chemie

Fomblin T4 2-Oxiranemethanol, polymers with reduced Me esters of reduced polymd. oxidized tetrafluoroethylene, Supplied by Solvay Solexis

Dow Corning Antifoam 1400: Silicone compound, supplied by Dow Corning

AO-802: Alumina, supplied by Admatechs

XG-1270: Silica, supplied by Gelest

SE6100 Spherical silica, Average particle size 1.8 μιη, supplied by

Admatechs company limited

SE1050 Spherical silica, Average particle size 0.8 μιη, supplied by

Admatechs company limited

Example 1

Preparation of the fill material 1

8.81 g of SR 495 B (Vinyl Resin), 8.33 g of RAS-1 (Epoxy Resin), 25.60 g of SRM-1 (BMI Resin), 5.12 g of Ricon 131 MA10 (Vinyl Resin), 0.48 g of Z6040 (Additive), 0.36 g of Z6030 (Additive), 0.36 g BYK-333 (Additive), 0.24 g of Catalyst 313B (Epoxy hardener), 0.71 g of Dicumyl Peroxide (Curing agent) and 50.00 g of AO-802 (Filler) were mixed together to prepare a fill material. The viscosity of the fill material at 5 rpm was measured as 3992 mPa-s and the viscosity thereof at 0.5 rpm was measured as 4643 mPa-s, so T.I. for the fill material 1 was 1.163. The data relating with DSC Peak for the fill material 1 was reported in Table 1.

Example 2

Preparation of the fill material 2

The fill material 2 was prepared in the same way as the fill material 1 , except that the amount of each component in the fill material 2 was changed according to the data shown in Table 1. Example 3

Preparation of the fill material 3

The fill material 3 was prepared in the same way as the fill material 1 , except that the amount of each component in the fill material 3 was changed according to the data shown in Table 1.

Table 1 The composition of the fill material in Examples 1-3

Example 4

Preparation of the dam material 4

7.64 g of SR 610 (Vinyl Resin), 6.11 g of EPON Resin 58005 (Epoxy Resin), 1.53 g of Art Resin UN 9200 (Vinyl Resin), 23.45 g of SRM-1 (BMI Resin), 9.27 g of Ricon 131 MA10 (Vinyl Resin), 0.24 g of Catalyst 313B (Epoxy hardener), 0.22 g of Dicumyl Peroxide (Curing agent), 0.33 g of Dow Corning Antifoam 1400 (Additive), 0.44 g of Z6040 (Additive), 0.33 g of Z6030 (Additive) and 50.70 g of XG-1270 (Filler) were mixed together to prepare a dam material 4. The viscosity of the dam material at 5 rpm was measured as 44370 mPa-s and the viscosity thereof at 0.5 rpm was measured as 164400 mPa-s, so T.I. for the dam material 4 was 3.705. The data relating with DSC Peak for the dam material 4 was reported in Table 2. Example 5

Preparation of the dam material 5

The dam material 5 was prepared in the same way as the dam material 4, except that the amount of each component in the dam material 5 was changed according to the data shown in Table 2.

Example 6

Preparation of the dam material 6

The dam material 6 was prepared in the same way as the dam material 4, except that the amount of each component in the dam material 6 was changed according to the data shown in Table 2.

Table 2 The composition of the dam material in Exampli

Example 7

Preparation of the paste material 7 5.46 g of SR 495B (Vinyl Resin), 6.12 g of EPON Resin 58005 (Epoxy Resin), 1.95 g of Art Resin UN 9200 (Vinyl Resin), 23.48 g of SRM-1 (BMI Resin), 10.92 g of Ricon 131 MA10 (Vinyl Resin), 0.27 g of Fomblin T4 (Additive), 0.44 g of Z6040 (Additive), 0.33 g of Z6030 (Additive), 0.24 g of Catalyst 313B (Epoxy hardener), 0.44 g of Dicumyl Peroxide (Curing agent), and 43.80 g of SE 6100 (Filler) and 6.55 g of AO-802 (Filler) were mixed together to prepare a paste material 7. The viscosity of the paste material at 5 rpm was measured as 21990 mPa-s and the viscosity thereof at 0.5 rpm was measured as 45420 mPa-s, so T.I. for the paste material 4 was 2.065. The data relating with DSC Peak for the paste material 7 was reported in Table 3.

Example 8

Preparation of the paste material 8

The paste material 8 was prepared in the same way as the paste material 7, except that the amount of each component in the paste material 8 was changed according to the data shown in Table 3.

Table 3 The composition of the paste material in Exampli

Performance Example 9

The die bonding formed according to the D-F process

Thirteen groups of the die bonding test were performed according to the D-F process. Take Group #1 for example, the dam material 4 was first dispensed around a controller die, the viscosity (44370 mPa-s) thereof was higher than that of the standard die bonding (about 10000 mPa-s), and thus can keep its original shape. The nozzle size (internal diameter) for the dam material was 0.30 mm with a frame dispensing pattern. For dispensing the dam material, the air pressure was 0.34 MPa, the dispensing speed was 9 mm/s, and the dispensing height was 0.08 mm. The stage temperature was 25 ^°C . The fill material had very low viscosity and T.I., which can have very good flow-ability at BGA substrate. The nozzle size for the fill material was 0.50 mm with a maze v2 dispensing pattern. For dispensing the fill material, the air pressure was 0.12 MPa, the dispensing speed was 37.5 mm/s, and the dispensing height was 0.14 mm. The substrate was slightly heated to improve the flow and coverage. The stage temperature was 65 ^°C . After the fill material was filled and got full coverage, the fill material was pre-heated to form a tacky surface. Then, a memory die was attached thereon. The Bond force was 200g and the bond time was 1000 ms. The partially cured material was then put into an oven for complete cure. After curing, die bond result is shown in Table 4, that is, the BLT was 80 μιη, the adhesion at room temperature was 4.3 kgf/mm² and the strip warpage was 50 μιη. The other twelve groups were performed in the same way as for Group #1 except that the corresponding process parameters were changed in accordance with those shown in Table 4.

Table 4

From Table 4, it can be clearly seen that the performance of the D-F process are superior in terms of BLT, adhesion at room temperature and strip warpage. It is proven that BLT is controllable according to the inventive D-F process, such as in the range of from 80 to 200μιη. Adhesion at room temperature according to the inventive D-F process is equal to or more than 3.9 kgf/mm², which is much higher than the average value of around 2.5 kgf/mm² in the prior art. Strip warpage is even better since it is much less than 100 μιη, which means that on one hand the warpage according to the inventive process is not visible by naked eyes, and on the other hand, it is better than the average value of higher than 100 μηι in the prior art.

Performance Example 10

The die bonding formed according to the printing process

Eight groups of the die bonding test were performed according to the printing process. Take Group #1 for example, a printed steel stencil having a thickness of 125 um with a set of particular apertures was used to cover a controller die on a substrate, then the paste material 7 was printed into the apertures so as to cover the controller die. The squeegee pressure was 1 kg, with a squeegee speed of 10 mm/sec and a separation speed of 0.5 mm/sec. The paste material was partially cured. Then, a memory die was attached onto the paste material. The Bond force was 200 g and the bond time was 1000 ms. The partially cured material was then put into an oven for complete cure. After curing, die bond result is shown in Table 5, that is, the BLT was 100 μιη, the adhesion at room temperature was 4.3 kgf/mm² and the strip warpage was 50 μηι. The other seven groups were performed in the same way as for Group #1 except that the corresponding process parameters were changed in accordance with those shown in Table 5.

Table 5

From Table 5, it can be clearly seen that the performance of the printing process are superior in terms of BLT, adhesion at room temperature and strip warpage. It is proven that BLT is controllable according to the inventive printing process, such as in the range of from 80 to ΙΟΟμιη. Adhesion at room temperature according to the inventive printing process is equal to or more than 4.06 kgf/mm², which is much higher than the average value of around 2.5 kgf/mm² in the prior art. Strip warpage is even better since it is much less than 100 μιη, which means that on one hand the warpage according to the inventive process is not visible by naked eyes, and on the other hand, it is better than the average value of higher than 100 μιη in the prior art.

While the disclosure has been described in the specification and illustrated in the drawings with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various embodiments is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this disclosure, but that the disclosure will include any embodiments falling within the foregoing description and the appended claims.

Claims

What is claimed is:

1. A process for die bonding, which utilizes a dam material and a fill material, characterized in that it comprises the following steps:

1) a dam material is dispensed around one or more first die on a substrate;

3) optionally, the fill material is partially cured;

4) a second die is bonded onto the fill material;

5) The dam and fill material is completely cured.

2. The process for die bonding according to claim 1, characterized in that the viscosity of the dam material at 5 rpm at 25 ^°C is in the range of 5,000-500,000 mPa-s, preferably in the range of 40,000-50,000 mPa-s, the thixotropic index (T.I.) of the dam material is more than 1.0, preferably from 4.0-6.0.

3. The process for die bonding according to claim 1 or 2, characterized in that the viscosity of the fill material at 5 rpm at 25 ^°C is in the range of less than 50,000 mPa s, preferably less than 10,000 mPa-s, the T.I of the fill material is less than 3.0, preferably less than 1.5.

4. The process for die bonding according to any one of claims 1 to 3, characterized in that the dam material comprises basic resin, epoxy hardener, curing agent, filler, and other additives, wherein the basic resin is one or more selected from the group consisting of Epoxy Resin, BMI Resin and Vinyl Resins.

5. The process for die bonding according to any one of claims 1 to 4, characterized in that the fill material comprises basic resin, epoxy hardener, curing agent, filler, and other additives, wherein the basic resin is one or more selected from the group consisting of Epoxy Resin, BMI Resin and Vinyl Resins.

6. The process for die bonding according to claim 4, wherein the dam material comprises 0-20%, preferably 4-8% of Epoxy Resin, 0-30%, preferably 20-28% of BMI Resin, 0-30%), preferably 14-20% of Vinyl Resins, 0-5%, preferably 0.2-1.0%) of epoxy hardener, 0-5%, preferably 0.2-1.2% of curing agent, 30-80%, preferably 40-60% of filler and 0-5%, preferably 0.5-2.0% of other additives, based on the total weight of the dam material, and the sum of each component being 100%.

7. The process for die bonding according to claim 5, wherein the fill material comprises 0-30%, preferably 8-16% of Epoxy Resin, 0-40%, preferably 25-30% of BMI Resin, 0-40%, preferably 6-16% of Vinyl Resins, 0-5%, preferably 0.2-1.2%) of epoxy hardener, 0-5%, preferably 0.6-1.0% of curing agent, 0-70%, preferably 45-50%) of filler and 0-5%, preferably 0.8-1.5% of other additives, based on the total weight of the fill material and the sum of each component being 100%.

8. The process for die bonding according to any one of claims 1 to 7, characterized in that the first die is a controller die and the second die is a memory die.

9. A printing process for die bonding, which utilizes a printed steel stencil and a paste material, characterized in that it comprises the following steps:

3) optionally, the paste material is partially cured;

4) a second die is bonded onto the paste material; and

5) the paste material is fully cured.

10. The printing process for die bonding according to claim 9, characterized in that the viscosity of the paste material at 5 rpm at 25 ^°C is in the range of 1 ,000-500,000 mPa-s, preferably in the range of 15,000-50,000 mPa-s, the T.I. of the paste material is more than 1.0, preferably from 1.5-3.0.

11. The process for die bonding according to claim 9 or 10, characterized in that the paste material comprises basic resin, epoxy hardener, curing agent, filler, and other additives, wherein the basic resin is one or more selected from the group consisting of Epoxy Resin, BMI Resin and Vinyl Resins.

12. The process for die bonding according to claim 11 , wherein the paste material comprises 0-30%, preferably 5-10% of Epoxy Resin, 0-30%, preferably 20-30% of BMI Resin, 0-30%, preferably 15-28% of Vinyl Resins, 0-6%), preferably 0.2-1.5% of epoxy hardener, 0-5%, preferably 0.2-1.0% of curing agent, 30-70%, preferably 30-55%> of filler, and 0-5%, preferably 1.0-1.5% of other additives, based on the total weight of the paste material and the sum of each component being 100%.

13. The process for die bonding according to any one of claims 9-12, characterized in that the first die is a controller die and the second die is a memory die in a memory card.

14. Memory card, especially embedded Multi Media Card prepared according to any one of claims 1 to 13.