JP2003527736A - Flip chip device using flexible conductive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flip-chip device using a flexible conductive adhesive having a low elastic modulus by using a flexible conductive adhesive. An electronic device (10, 100) includes one or more semiconductor chips (30, 130) interconnected to a next level substrate (20, 120). The flexible conductive adhesive (40, 140) is conductive on the contact pads (24, 124) of the substrate (20, 120) or on the contact pads (34, 134) of the semiconductor chip (30, 130). Flexible thermoplastic or thermoset resin applied as conductive bumps (40, 140) and filled with conductive particles. Other electronic devices (44, 46, 144, 146), such as packaged components including resistors, capacitors, etc., have the same flexible conductive properties as those used for semiconductor chips (30, 130). It is joined by an adhesive bump (24, 124, 34, 134) approach. The contact pads on both the chip (30, 130) and the next level substrate (20, 120) must have a metallic coating (38), preferably a noble metal, before internal connection to prevent oxidation of the pads (37). It is preferably protected by A flexible insulating organic underfill (150) may be used, and preferably has a modulus that is substantially as low as the flexible conductive adhesive (40, 140).

Description

DETAILED DESCRIPTION OF THE INVENTION       [0001]   The present invention relates to US Provisional Patent Application No. 60/082, filed April 24, 1998.
U.S. Provisional Application No. 60/092, filed July 9, 1998,
No. 147, U.S. patent application Ser. No. 09 / 166,6, filed Oct. 5, 1998.
No. 33, U.S. Provisional Application No. 60 / 083,3, filed April 28, 1998.
No. 26, and U.S. patent application Ser. No. 09/276, filed Mar. 25, 1999.
, 259.       [0002]     TECHNICAL FIELD OF THE INVENTION   The present invention relates to an electronic device, and more particularly, to an electronic device having a semiconductor chip bonded to an upper portion thereof.
About.       [0003]     [Prior art]   Since the invention of integrated circuits in the early 1960's, their use has rapidly increased,
Is not necessary for many electronic products that traditional societies have relied on and taken for granted
It is missing. Mount circuits and other semiconductor chips into a functional form
Although there are many methods, the physical size of the electronic device implemented in this way is small,
If the installed electronic device is low cost, its effectiveness will be further enhanced.
Will be.       [0004]   Conventionally, the upper surface of a semiconductor chip (that is, one side of a chip on which an electronic circuit is formed)
Lead pads, headers or other
A loop is formed on the package or the substrate to which the bottom of the semiconductor chip is attached.
Connections to semiconductors are made using fine gold or aluminum bond wires
ing.       [0005]   The technology of bond wire interconnection is that each bond wire costs one cent (.0 cents).
(US $ 01). Roux over a relatively short distance
Is necessarily undesirable due to the electrical properties of the thin bond wire
As the inductance and capacitance fall into the interconnect, the bandwidth and
Operation speed decreases. High speed microprocessor, high frequency signal processing and communication equipment
As a result of its development, this restriction has become more important in recent years.       [0006]   One way to reduce the capacitance and inductance of these interconnects is to use
There is a method of shortening the length of the interconnection path. Traditional effective to achieve this
One method is to turn over the semiconductor chip (ie, "flip chip"
The contact pad is closely attached to the substrate and
The contact pads on the substrate are directly connected to the semiconductor contact pads.
A corresponding set is formed.       [0007]   L. F. Miller, "Method of Joining Components to Substrate (Method of
  Joining a Component to a Substrate)
U.S. Pat. No. 3,429,040, entitled "No.
A flip-chip arrangement that is attached to a substrate by bumps is disclosed. free
The distance between the chip and the substrate has been about 50-100 micrometers (1
Micrometer is also known as 1 micron)
Operation at a very high frequency becomes possible.       [0008]   Interconnects of semiconductor devices in flip-chip structures are made of very sophisticated metal
Appropriate height conductive bumps used for connections using cladding and metallurgy
Use low-cost solder bumps, which are not so demanding.
Has evolved.       [0009]   Soldering and solder bump technology as well as metallurgy are the low temperature of such interconnects.
For changes in deposition composition and method suitable for high temperature and high temperature reflow soldering
As described above, it may be changed using a known method. Specific control of solder bump technology
The limitation is that the semiconductor device has an organic substrate because the coefficient of thermal expansion (CTE) of the material is different.
Appears when it can be attached directly to       [0010]   For example, the CTE of an FR-4 glass fiber substrate is 17 ppm / ° C.
On the other hand, the CTE of the semiconductor chip is 3 ppm / ° C. Similarly, CTE is 7pp
Even when flip-chip interconnections are made on alumina substrates with only m / ° C
The size of the semiconductor chip is greater than 5 mm at each end
, With considerable limitations.       [0011]   The solder joint has a modulus of about 700,000 kg / cm²(0.0703
kg / cm²= 1,000,000 psi, about 10,000,000 psi)
Due to lack of flexibility, solder joints can cause fatigue failure when subjected to periodic temperature fluctuations
Will be.       [0012]   Fujita et al., “Conductive Conductive Adhesive Connection Array (Electrical)
y Conductive Adhesive Connecting Arr
US Patent No. 4,113,9 entitled "Ays of Conductors".
No. 81 has almost no conductive effect except when compressed.
Non-conductive adhesive bases filled with no conductive particles are disclosed.       [0013]   Fujita et al. Use such adhesives to attach raised contacts.
The method discloses a non-contact adhesive, which is typically a non-contact adhesive on a non-conductive adhesive.
Conductive particles are pressed against the bumps of the device, causing the bumps
Contacts electrically connect to the raised contact pads on the substrate and then
The contacts in contact with each other are separated by the insulating resin.       [0014]   In conventional semiconductor wafers, aluminum contact pads are usually
It has a depression below a typical insulating inorganic passivation layer. Fujita Patent
One of the limitations is that the contours above the top surface of the insulating passivation layer or substrate
May need to be extended.       [0015]   Prepare as part of the semiconductor wafer assembly process or prepare as a separate process
Or, in any case, that this need to be done
The cost of semiconductor devices and interconnects tends to increase. Fujita's
Another limitation on interconnects is that only a limited number of conductive paths can be
May not be formed in the tact, so that electrical connection between only a few conductive particles
It is not practical because the isolation renders the interconnect non-conductive.       [0016]   For many years now, isotropic conductive adhesives have been used to contact semiconductor die contact pads.
Bond the backside of the semiconductor die to the package before connecting the wires to the package leads
Used in hybrid circuit assemblies and printed distribution
Semiconductor components, chip resistors and chip capacitors in wire plate assembly
Widespread use has also been made for mounting.       [0017]   Regarding the initial use of conductive adhesive for flip chip bonding, Proceed
ings of IEEE Electronic Component Co
nreference, 1967 (pp. 269-275)
"Flip-Component Technology"
In a dissertation, proposed by Scharf et al. In this paper,
A substrate having an array of 16 bond pads for each semiconductor die
The conductive adhesive bump is copied.       [0018]   Schaff et al. Describe a good stencil creation method for printing elaborate bumps.
Benefits of using conductive adhesives such as low temperature bonding and low cost
Are listed.       [0019]   Next, P. "Multiple electrical connections between two electrical elements" by Jourdain et al.
Method of forming connections simultaneously (Method of Simultaneously
  Manufacturing Multiple Electrical C
connections Between Two Electrical El
U.S. Pat. No. 4,442,966, entitled "Elements".
The use of conductive paste to bond aluminum pads to substrates is now open.
Shown here, where a conductive adhesive bump is deposited on the contact pads.
The Tensil method is used to apply pressure and heat to the substrate during semiconductor assembly.
ing.       [0020]   Using such a conductive epoxy adhesive to join the semiconductor chips,
Applying such an adhesive is described in, for example, K. Gilleo's "Polymer Bonding
Direct chip interconnect used (Direct Chip Intercon
connect Using Polymer Bonding) ", 39th El
electronic Component Conference, May 19
89, (pp. 37-44) and US patents.
I have.       [0021]   The limitations of the rigid conductive adhesive here are similar to those of the solder bump approach
That is, the connection is easily broken under temperature fluctuation. Reported response
Adhesive joint for use has a modulus of elasticity of 70,000 kg / cm²(1,000,
000 psi) or more, so there is almost no flexibility,
Excessive temperature fluctuation will cause delamination or breakage.       [0022]   Therefore, the main problem with chip-to-component or chip-to-board interconnects is
The coefficient of thermal expansion of the semiconductor chip silicon and the next level plate, ie, the semiconductor chip
Is the internal stress resulting from the difference between the coefficients of thermal expansion of the substrate to which it is attached.       [0023]   Conventional conductive adhesives and solder bump technology both result from these high stresses.
Destruction degrades their function, and these destructions are
As described above, extreme temperature differences and sizes are further exacerbated by large chips.       [0024]   One conventional solution to the stress problem is the use of areas that do not include conductive adhesive connections.
There is a method of dispersing stress using an epoxy underfill. Appropriate
The use of underfill also increases the size and temperature variation of the semiconductor die.
However, the number of thermal cycles that enhances the tolerance of such interconnects is increased by a factor of 6 to 8
The advantage of a high-strength underfill that suppresses periodic distortion
Compressive stress and destructive effects that cause delamination and joint or component failure
The inherent problem of balancing with high shear stress still remains.       [0025]   As the size of the semiconductor die increases, so does the shear stress,
The reliability of flip-chips assembled under a specific temperature range
Needs to be re-evaluated. Similarly, the extreme value of the temperature fluctuation range is lower or higher
Costly reassessment tests are required and
Additional shear stress can adversely affect tip reliability.       [0026]   By appropriately increasing the elasticity of the underfill, it can withstand temperature fluctuation stress.
Can increase the capabilities of flip-chip device assemblies
Nevertheless, the size of available semiconductor devices and the heat
It is limited by both the coefficient of expansion and the difference between the coefficient of thermal expansion of the next level of substrate.       [0027]   Also compare the cost of incorporating such a rigid adhesive underfill
High and high strength adhesive underfill makes repair and rework quite difficult
(Sometimes not possible at all)
The cost of the embedding device is further increased.       [0028]   Another possible solution to the problem of this technology involves the next level of plate, namely the substrate
And the same thermal expansion coefficient as that of the semiconductor chip, for example, about 3 ppm / ° C.
There is a method of giving a thermal expansion coefficient of Some use this technical approach to ask questions.
Some of these problems have been solved, but the cost of developing and manufacturing such substrates is high.
Undesirable and necessary infrastructure development to support these new technologies
Not widely used.       [0029]   To complicate matters, the least expensive common electronic boards are
Such as FR-4, which is commonly used for wire circuit boards and has a CTE of 17 ppm / ° C.
This is to provide a glass fiber laminate using an epoxy resin. Conventional commercial power
Most of the slave devices employ FR-4 printed circuit boards without exception. But
Costly and require additional intermediate substrates, or for FR-4
Alternate special substrate materials will either be required.       [0030]   Therefore, the difference in the coefficient of thermal expansion between the silicon of the semiconductor chip and the next level plate
Compatible, chip-scale mounting on a functional circuit board and direct chip removal
There is a need for an interconnect technology that can be both attached.       [0031]     DISCLOSURE OF THE INVENTION   For this reason, the present invention has a contact pad on the top which is protected by a noble metal.
A semiconductor chip, which is protected by a noble metal.
Flip-chip connection to substrate with corresponding contact pads on top
. The connection between the semiconductor chip and the corresponding contact pad on the substrate has an elastic modulus
Made with low flexible conductive adhesive.       [0032]   The detailed description of the preferred embodiments of the present invention will be more easily and deeply understood with reference to the drawings.
Will be understood.       [0033] BEST MODE FOR CARRYING OUT THE INVENTION   Certain embodiments of the invention described herein are described for explanatory and illustrative purposes.
The present invention is not intended to limit the present invention.
Used in various embodiments without departing from the scope and spirit of the invention.
Please understand that it may be.       [0034]   In general, the present invention relates to a substrate and electronic components mounted thereon, such as a semiconductor.
Flip chip devices including devices, resistors, capacitors and other components
Interconnection between components, such as, is made by a flexible conductive adhesive with a low modulus of elasticity
In order to prevent fatigue and delamination,
The difference in the coefficient of thermal expansion (CTE) between the electronic component and the substrate can be reduced to 60 ppm / ° C without using
An electronic device that provides substantial flexibility to fit.       [0035]   Increases electrical isolation and reduces migration of certain metals used as conductors
If any underfill is used, such as when
Underfill such as must be flexible with low elastic modulus and flexible
The same or lower than the elastic modulus of the conductive adhesive interconnect
Is preferred.       [0036]   The electronic device 10 of FIG. 1 includes an insulating substrate 20, on which a semiconductor chip is mounted.
30, a plurality of electronic devices such as a chip resistor 44 and a chip capacitor 46.
Are aligned and mounted. In this embodiment, the devices 30, 44, 46
There is no insulating underfill between the substrates 20.       [0037]   The semiconductor chip 30 includes the semiconductor chip 30 on the first surface of the substrate die 32.
Multiple contours for electrical connection between the electronics and external electronic components
And a touch pad 34. Similarly, each of the resist 44 and the capacitor 46
Included on each first surface are a chip resistor 44 and a chip capacitor 46, respectively.
Between the resistive and capacitive circuit elements and external electronic elements through the substrate 20
And a plurality of contact pads for electrically connecting.       [0038]   Substrate 20 has a first surface on which a conductor of an electronic circuit is formed in a conventional manner.
It includes a lint wiring conductor 22. On the conductor 22 of the substrate 20, an electric current placed on the substrate is placed.
Bonding pads 34, 45, 47 respectively corresponding to the child devices 30, 44, 46
A plurality of contact pads 24 are formed at positions corresponding to the positions of. Paraphrase
If so, the arrangement, size and spacing of the contact pads 24 on the substrate 20 are
Compatible with the arrangement, size and spacing of the contact pads 34 of the vice 30
is there.       [0039]   The substrate 20 is made of a laminate such as FR-4 glass fiber or BT material, or is coated.
Aluminum or alumina, ceramic or other suitable insulating material
The conductor 22 on the substrate may be made of gold, such as copper, aluminum, gold or silver.
Or conductive formed by known techniques such as thin film or thick film deposition methods
It may be formed by ink.       [0040]   Contact pads on conductors must be made of non-oxidizing materials such as noble metals
For example, to obtain constant and stable electrical contact over a long period of time,
The contacts must be protected by coatings or alloys,
The same is true for       [0041]   The electronic devices 30, 44, 46 are each located closest to the first surface of the substrate 20.
Provided on the first surface of the electronic device 30, 44, 46.
The pads are adjacent to respective corresponding contact pads on substrate 20, ie,
Adjacent in flip-chip format.       [0042]   The electronic devices 30, 44, 46 are mounted on a plurality of flexible conductive adhesive bumps 40.
Are attached to the substrate 20, and these bumps allow each device 30,
44, 46 are mechanically attached to the substrate 20 and each contact pad 3
4, 45, 46 and the corresponding contact pads located on the substrate 20 are low.
Electrical connection is made with an impedance, usually 0.1 ohm or less.       [0043]   The fact that the conductive adhesive 40 needs to be "flexible" means that
, Its elastic modulus is low. The composition to be filled has an elastic modulus of about 35.
2,000kg / cm²(Approximately 500,000 psi).
Is required. The adhesive is a thermoplastic or thermosetting resin or a mixture of them
Or may contain a copolymer, in which fine particles of a conductive material are contained.
Being included makes it conductive, which also has a higher modulus than pure resin
It will be lost.       [0044]   A suitable flexible conductive adhesive is LTP8150 type liquid flexible thermoplastic conductive
Adhesive, ESS 8450 type (silver filler), ESS 8456 type (silver-palladium)
Alloy filler), ESS8457 (gold-plated copper filler), ESS84
58 type (gold powder filler), ESS8459 type (gold plated nickel filler)
Flexible epoxy adhesive paste and PSS8156 type (silver-palladium alloy
Filler), PSS8157 (gold-plated copper filler), PSS8158
(Gold powder filler), PSS8159 (gold plated nickel filler) flexibility
Including paste adhesives, all of which are located in Princeton, NJ
-AI Technology, Inc. (AI Technology,
Inc. ).       [0045]   The glass transition temperature of these flexible conductive adhesives is about -55C to -60C.
Therefore, as shown in FIG. 2, its elastic modulus is about 35,000 kg / cm at a low temperature.² (Approximately 500,000 psi). PSS8150 type flexible conductive adhesive
Means that the glass transition temperature is lower than -20 ° C and the elongation percentage of the dimension before fracture exceeds 30%
Containing thermoplastic resin. ESS 8450 type flexible conductive adhesive is made of glass
Modified thermoset having a transition temperature lower than 0 ° C and an elongation percentage of linear dimension before rupture exceeding 30%
Including curable epoxy resin. Thermoplastic tree whose melting point temperature that can flow is lower than 300 ° C
Fat is preferred.       [0046]   FIG. 2 shows the elastic modulus (p) as a function of temperature (° C.) for various conductive adhesives.
The graph of si) is shown. Elastic modulus of conventional adhesives such as solder and epoxy
Is approximately 70,000 kg / in most of the temperature range where semiconductor devices are normally operated.
cm²(About 1,000,000 psi). Semiconductor
The vice's normal operating temperature range is limited to the requirements of automotive, aircraft and military applications.
For devices intended for high applications, the temperature is -55 to + 150 ° C.
Devices intended for less demanding applications, such as those for garden appliances, have a specified temperature range of
It may be narrower.       [0047]   The elastic modulus of the flexible conductive adhesive used in the present invention depends on the operation of the semiconductor device.
About 35,000 kg / cm at least about 50% of the operating temperature range²(about
500,000 psi). The preferred modulus of the adhesive is ESS8459
As shown, in such a temperature range, about 7,000 kg / cm²(About 100
2,000 psi), and is further represented by model PSS8159.
About 3,500kg / cm²(About 50,000 psi)
The glass transition temperature of both conductive adhesives is about -55 to -60.
° C.       [0048]   Suitable conductive fillers for flexible conductive adhesives include silver, gold, palladium or plastic.
Tina particles (flakes, spherical or powder), silver-palladium alloy particles, and gold plating
Copper or nickel particles, which are provided by AI Technology.
, Inc. Included in the various fillers of the flexible conductive adhesive described above available from
It is rare.       [0049]   The silver-palladium alloy powder filler has a palladium proportion of at least about 10-3.
In the 0% range, it is most resistant to silver migration,
The greater the percentage of the alloy, the greater the resistance to silver migration
Is high, but the cost of the filler can be quite high for many applications
. Other alloys of noble metals are also suitable. According to the present invention, the contact using a flexible conductive adhesive is performed.
After the contact, the contact resistance can be reduced to 0.1 ohm or less.       [0050]   In addition, one suitable flexible conductive adhesive is gold plated or palladium plated.
And a conductive filler containing coated copper flakes. Another suitable flexible conductive adhesive is gold.
Including conductive fillers, including nickel flakes plated or palladium plated
No. Other non-precious metals such as aluminum and other non-precious metal alloy cores
It may be used effectively with a stick. Core material and plating material, plating cost
And may be selected based on ease.       [0051]   Another flexible conductive adhesive has a volume electrical resistance of less than 0.00009 ohm-cm.
Low through special interconnects by being formed of specially prepared silver particles
To allow more current to flow, that is, to increase the current density at the interconnect.
Can be higher. Conductive fillers are limited to those specifically mentioned above
However, the filler particles may be precious if the core of the particles is not precious.
At least protection should be provided by coating or plating metal to make it resistant to oxidation.
Note that this must be done.       [0052]   Gold, palladium and platinum coated metal flakes and powders
The genus coating should be greater than about 5% by weight, for example, if the precious metal coating is too thin.
To prevent long-term high-temperature oxidation, which can slowly degrade the bulk electrical resistance characteristics of the filler
Must provide stability. The precious metal coating is about 50% of the total filler
%, The cost effectiveness of using the coated metal is lost. Electrical characteristics and
To satisfy cost effectiveness, gold content in the range of about 5-30% by weight is effective
It is a target.       [0053]   Therefore, the above-mentioned ones have a low elasticity and therefore have flexibility and
Low cost, less susceptible to stress due to inherent CTE difference between plate 20 and substrate 32
Interconnection by flexible conductive adhesive. 12mm without underfill
In a typical example of the aforementioned electronic device including a 12 mm semiconductor device, -55 ° C to +1
After 1000 cycles in a temperature range of 50 ° C and between -65 ° C and + 150 ° C at each temperature.
50 cycles of temperature shock with 10 minutes residence time and 10 seconds transition time between temperatures
After more than one cycle, no deterioration in bond strength and contact resistance was measured.       [0054]   The foregoing uses a flexible conductive adhesive to interconnect a semiconductor chip to a substrate.
The superiority of electronic devices can be compared to published thermal cycling data
Will be easily understood.       [0055]   Rosner et al., "Flip chip bonding using isotropic conductive adhesive (Fli
p Chip Bonding Using Isotropic Condu
active Adhesives) ",Proceeding of Elec Tronic Component and Technology Conf erence May, 1996 (pp. 524-581) and Wu et al.
Material and Structural Issues in Chip-to-Chip Organic Packaging (Materials a
nd Mechanics Issues in Flip-Chip Org
anic Packaging) ",Electronic Component ts and Technology Conference , May, 199
6 (pp. 524-534) and Gamota et al.
Encapsulation Material System (Advanced Encapsulant Mat)
erial Systems for Flip Chip) "Advanc ing Microelectronics , July / August, 199
7 (pp. 22-24) recently showed that solder bump adhesion and
Reliability and improvement of contact resistance as a function of thermal cycling for the adhesion of rigid conductive adhesives
Has been reported. Solder bump without underfill and rigid conductivity
Both samples of the adhesive interconnect were subjected to thermal support in the mid-range between -25 ° C and + 125 ° C.
If it receives a cycle, it will fail within 100 cycles.       [0056]   One way to assemble an electronic device of the type shown and described in connection with FIG. 1 above
The method may be understood in connection with FIGS. In FIG. 3, shown in plan view
Semiconductor substrate 32 has a plurality of contact pads or bonding pads 3 on its upper surface.
4 inclusive. The contact pad 34 is designed according to the design of the semiconductor device 30.
, Around the substrate 32, inside the substrate 32, or both as shown.
May be provided. Area of substrate 32 not including contact pad 34
The area is protected by an inorganic nitride such as silicon nitride or other insulating coating,
Does not receive conductive adhesive.       [0057]   As described below, the bumps of the flexible conductive adhesive 40 may have multiple contacts.
It is applied to each of the pads 34. Required for ease of processing and low cost
If this is the case, an adhesive may be applied to the individual substrates 32, but the wafers are notched.
Before the individual substrate dies are separated, bumps of flexible conductive adhesive
Preferably, the bell is applied to all of the substrates 32 formed thereon.       [0058]   FIG. 4 is a cross-sectional view of the semiconductor device of FIG. 3 taken along line 3-3. Contour
The contact pad 34 is deposited on the semiconductor substrate 32, and a circuit (see FIG.
(Not shown) is placed at a position where the electrical contact is made to function electrically.
It has a minium pad 37, which is preferably nickel
Non-oxidizing metals in the order of gold and gold, gold, silver, platinum, palladium or
Protected by depositing a metal 38 of another noble metal, such as an alloy of Also,
Kel and chromium may be used as non-oxidizing passivation. Also, the substrate 20
Contact pads 24 are also protected by the non-oxidizing metal. Inorganic passivation
The thickness of layer 36 is greater than the thickness of contact pad 34, which
Above is common but not a requirement.       [0059]   In FIG. 5, a plurality of flexible conductive adhesives are provided on a plurality of contact pads 34.
A bump 40 is deposited. The flexible conductive adhesive bump 40 is made of AI Tech.
Liquid Thermoplastic Conductive Adhesive LTP marketed by Nology, Inc
Nip the contact pad 34 with a flexible thermoplastic conductive adhesive such as 8150.
It is deposited and formed on the Kel-Gold passivation layer 38. Of resin and silver filler
The ratio is preferably between about 100: 100 and 100: 600,
In this case, the volume resistance becomes about 0.00015 ohm-cm.       [0060]   The viscosity of the mixture of liquid thermoplastic adhesive and silver flake is determined by the strike in Massachusetts.
Brookfield Company
y), using a viscometer commercially available from
Up to approximately 200,000 cp when measured at the Eastman Kodak rate
By Eastman Kodak Chemicals
using an ester alcohol solvent such as that marketed under the trade name exanol
And adjusted.       [0061]   The flexible conductive adhesive for forming the bump 40 has a bump size of 75 micron.
Standard stencil or stencil or
Use a clean method or use inkjet printing, contact deposition, pre-
It may be deposited by a foam laminate or other suitable deposition means. The bump is
It may be circular or rectangular.       [0062]   The size and shape of the bump is not critical for most applications, but the dimensions of the bump 40
The dimension (diameter) is larger than at least the dimension (diameter) of the contact pad 34.
And the lowest possible contact resistance when assembled into the final device 10
It is preferable to make       [0063]   The liquid thermoplastic paste has a wetting thickness of 75-125 micrometer.
Sediment can be dried at 60-80 ° C. for 30-60 minutes
. The resulting height of the adhesive bumps 40 when dry is approximately equal to the wetting thickness.
50% to 60%, and bumps have 90% bump height with an accuracy close to 98% in diameter
It becomes almost uniform with an accuracy close to.       [0064]   The height of the dried bumps is approximately 50-100 micrometers. Flexible guide
The electrically conductive adhesive bumps 40 are made of a material such that the aluminum bonding pad 37 is made of nickel to prevent oxidation.
Deposited when the semiconductor chip 30 is in wafer form after being protected by the gold layer 38
Preferably.       [0065]   Furthermore, the wafer having the conductive bumps 40 on the upper side is 200 ° C. for 1 to 5 seconds.
Exposure to temperature enhances adhesion between adhesive bump 40 and contact pad 34
. The prepared wafer may then be diced into individual substrate dies,
May be stored at ambient temperature and subsequently assembled into an electronic device.       [0066]   Prepared half with flexible conductive adhesive bumps on top as shown in FIG.
The conductor device 30 is assembled to the next level plate, the substrate 20, and
An electronic device 10 as shown in FIG. 1 is formed as described below. The semiconductor device 30 is
The contact pads 24 and 34 of the board 20 and the semiconductor device 30 are aligned.
Aligned over the substrate 20 so that       [0067]   The device 30 and the substrate 20 are pressed together and the temperature is in the range of 195 to 215 ° C.
The installation pressure is about 0.7kg / cm²(About 10 psi), flexible adhesive
The bumps 40 instantly join the respective contact pads together. More efficient
The substrate 20 is preheated to a temperature of about 150-200 ° C.
On the other hand, the chuck for picking up the semiconductor chip 30 is preset to about 220 to 280 ° C.
Is heated.       [0068]   Including a semiconductor die 30 bonded on an alumina substrate 20 and having an edge size exceeding 10 mm.
The electronic device 10 assembled as described above has a temperature between −65 ° C. and + 150 ° C.
More than 00 heat cycle and more than 50 temperature shock between -65 ° C and + 150 ° C
It has been found to be tolerant and has no measurable change in contact resistance.       [0069]   Electrical contact resistance after exposure to 85 ° C. at 85% relative humidity (RH) for 168 hours
No measurable degradation at all, and 1 hour at 100% RH for 200 hours.
Even when exposed to 00 ° C., the shear adhesive strength of the die 30 to the substrate 20 can be measured.
No deterioration was observed. Thick and thin gold bonding pads are full on alumina substrate
It was shown that it could be added.       [0070]   The equipment and temperature used in the assembly method described above may vary depending on the reflow soldering.
Used in conventional installation and installation of flip chip devices with solder bumps.
It is compatible with the one that was used. In any case, flip chip device
The contact pads on the chair are aligned with the corresponding contact pads on the substrate,
At a temperature lower than 300 ° C and 0.7 kg / cm²Pressure lower than (10 psi)
Pressed together by force and joined within about 10 seconds.       [0071]   The embodiments described above with respect to FIGS. 1 to 5 can be used without the need for underfill.
Although not used, use an underfill with appropriate flow characteristics.
In some applications it is desirable. Conduction between a mounting device such as a flip chip device and the substrate
The insulating adhesive material placed in the space between the electrical interconnects is the underfill.       [0072]   The mechanical flexibility and low internal stress that characterize the interconnectability of the interconnect according to the invention
In order to keep it, a suitable underfill material is used between the semiconductor device and the substrate.
The modulus of elasticity of the flexible conductive adhesive used for the conductive interconnects
Lower elastic modulus, ie about 35,000 kg / cm²(About 500,000
Non-conductive flexible adhesives with lower than psi).       [0073]   The electronic device 100 of FIG. 6 includes an insulating substrate 120 on which a semiconductor chip is placed.
, A chip resistor 144 and a chip capacitor 146.
Electronic devices are aligned and mounted. The semiconductor chip 130
On the first surface, electronic circuits included in the semiconductor chip 130 and external electronic elements
It includes a plurality of contact pads 134 for electrically connecting between them.       [0074]   Similarly, each of the resist 144 and the capacitor 146 is also provided on each first surface.
, The resistors included in the chip resistor 144 and the chip capacitor 146, respectively.
Electrical connection between the external electronic elements via the substrate 120 and the capacitive circuit elements.
A plurality of contact pads.       [0075]   Substrate 120 forms on its first surface the conductors of the electronic circuit in a conventional manner.
The printed wiring conductor 122 is included. On the conductor 122 of the substrate 120, placed on the substrate
Bonding pads 1 respectively corresponding to the electronic devices 130, 144, 146 to be
34, 145, and 147, a plurality of contact pads 124
Is formed. In other words, the arrangement and support of the contact pads 124 on the substrate 120
The size and spacing are determined by the arrangement and size of the contact pads 134 of the semiconductor device 130.
Size and spacing.       [0076]   The substrate 120 is made of a laminate such as FR-4 glass fiber or BT material, or alumina.
Alternatively, it may be made of ceramic or other suitable insulating material, and the conductor 1 on the substrate
22 is a metal such as copper, aluminum, gold or silver, or a thin or thick film
It may be formed by a conductive ink formed by a known technique such as a deposition method.
.       [0077]   Contact pads on conductors must be made of non-oxidizing materials such as noble metals
For example, to obtain constant and stable electrical contact over a long period of time,
The contacts must be protected by coatings or alloys,
The same is true for       [0078]   Electronic devices 130, 144, 146 are closest to the first surface of substrate 120
The electronic devices 130, 144, 146 are provided on the respective first surfaces.
Contact pads on the substrate 120 correspond to the corresponding contact pads, respectively.
Adjacent.       [0079]   The electronic devices 130, 144, 146 include a plurality of flexible conductive adhesive bumps.
Each bump is attached to the substrate 120 by 140, and these bumps
The chairs 130, 144, 146 are mechanically attached to the substrate 120, and
The contact pads 134, 145, 146 and the corresponding
The contact pads are electrically connected with low impedance.       [0080]   The insulating flexible underfill 150 is a flexible conductive contact in the embodiment of FIG.
The gap between the device 130, 144, 146 and the substrate 120 not occupied by the adhesive
Substantially fills the space.       [0081]   Both the conductive adhesive 140 and the insulating adhesive 150 need to be “flexible”
That is, each elastic modulus is about 35,000 kg / cm² (About 500,000 psi).       [0082]   Suitable flexible conductive adhesives are available from AI Tein of Princeton, NJ
channel, Inc. 1 and is available from
And specified above. Non-conductive or insulating resin can be thermoplastic or thermosetting
Resin, available from AI Technology, Inc.
A plastic underfill such as EE7650-5 epoxy-based encapsulating material or
It may be selected from encapsulating materials, whose modulus of elasticity is 1050 kg /
cm²(15,000 psi) and its glass transition temperature is below -20 ° C.
Is also low.       [0083]   In addition to increasing the adhesive strength between the components 130, 144, 146 and the substrate 120,
Of the substrate 120, which is likely to occur when humidity is high, due to the flexible insulating underfill of
Of silver between contact pads of components 130, 144, 146
Is more likely to be prevented.       [0084]   One method of assembling an electronic device of the type shown and described in connection with FIG. 6 above is
, May be understood in connection with FIGS. FIG. 7 shows a plan view.
The semiconductor substrate 132 has a plurality of contact pads or bonding pads 13 on its upper surface.
4 inclusive. The area of the substrate 132 not including the contact pad 134 is made of silicon nitride.
Flexible non-conductive adhesive 1 protected by inorganic nitride or other insulating coating such as
Receive 50.       [0085]   As described below, the bumps of the flexible conductive adhesive 140
The pattern of the insulating flexible adhesive 150 applied to each of the
It is applied to the space between the flexible conductive adhesives. In terms of ease of processing and low cost
If desired, an adhesive may be applied to the individual substrates 132, but may be engraved on the wafer.
Before the individual substrate dies are scored and separated, a bump of flexible conductive adhesive 140 is applied.
And a pattern of non-conductive flexible adhesive 150 is formed thereon at the wafer level.
Preferably, it is applied to all of the substrates 132 that have been removed.       [0086]   Further, the insulating flexible adhesive 150 completely fills the space between the contact pads 34.
By not filling, the flexible adhesives 140, 150
During bonding to the substrate 120, the void can flow and be filled therein
.       [0087]   FIG. 8 is a cross-sectional view of the semiconductor device 130 of FIG. 7 taken along line 7-7.
Contact pads 134 are deposited on and formed on the semiconductor substrate 132
Circuit (not shown) is placed at a position where it is electrically contacted so as to function electrically.
Aluminum pad 137 which is provided.
Preferably, a layer consisting of nickel and gold, or nickel and palladium,
A metal of another precious metal, such as silver, platinum, palladium or their alloys
138 is deposited and protected. In the exemplary embodiment of FIG.
The thickness of the contact layer 136 is substantially the same as the thickness of the contact pad 134.
.       [0088]   A plurality of flexible conductive adhesive bumps 140 on a plurality of contact pads 134
Is deposited. Flexible conductive adhesive, as described above in connection with the embodiment of FIG.
Is commercially available from AI Technology, Inc.
Flexible thermoplastic conductive adhesive such as liquid thermoplastic conductive adhesive LTP8150
Agent on the nickel-gold passivation layer 138 of the contact pad 134.
Stacked and formed.       [0089]   Again, the size and shape of the bump is not important for most applications,
, The size of the bump 140 is at least larger than the size of the contact pad 134.
Larger, the highest possible contact resistance when assembled into the final device 100
It is preferable to make it lower.       [0090]   Similarly, the insulating flexible adhesive 150 fills the space between the bumps 140
It may be patterned or putted so that it does not completely fill this space
In some cases, it is preferable that the semiconductor substrate 130 is
When assembled with 20, flexible conductive adhesive 140 and flexible insulating adhesive
Both of the agents 150 become flowable.       [0091]   The pattern of the flexible conductive adhesive bump 140 and the flexible insulating adhesive 150 is
The aluminum bonding pad 137 has a layer 38 of nickel and gold for preventing oxidation.
When the semiconductor chip 30 becomes a wafer shape after being protected by another noble metal,
Preferably, they are deposited. The prepared wafer is then transferred to individual substrate dies.
The substrate die may be stored at ambient temperature and subsequently
It may be assembled in a device.       [0092]   Flexible insulation, along with deposition of a flexible conductive adhesive to form bumps 140
The deposition of the pattern of adhesive 150 is performed using a standard stainless steel stencil or stencil.
Use a clean method or use inkjet printing, contact deposition, pre-
It may be deposited by a foam laminate or other suitable deposition means.       [0093]   The flexible insulating adhesive used as the underfill is a suitable flexible conductive adhesive.
As with the adhesive, keep it at ambient temperature for a long time after deposition and drying and before final assembly and bonding.
It may be tubed. Examples of suitable materials are available from AI Technology, Inc. Or
Thermoplastic paste LTP7150 type and liquid epoxy LESP7 available from
It is a 450 type.       [0094]   LTP7150 cures at 60-80 ° C for 30-60 minutes to form a solid film
Deposited and B-staged thermoplastic paste. LESP7450
Is deposited to cure to form a solid film for 30-60 minutes at 60-80 ° C.
-A staged epoxy paste. These modified B-stages
Possible flexible adhesives are in pure resin form and have a total glass transition temperature below -55 ° C.
It has such a molecular structure.       [0095]   Both the B-staged flexible insulating adhesive is a flexible conductive adhesive bump.
Higher flow index and lower elastic modulus than This allows the insulating adhesive to
Protects the edge of the device as it flows into and fills the space near the edge
You. According to mechanical tests exposed to highly accelerated moisture and temperature,
The change was less than 20% and no delamination of the joint was observed.       [0096]   Large size silicon on aluminum substrate with CTE higher than 20ppm / ℃
Using these adhesives to join semiconductor die (16 mm edge size)
The built electronic device is subjected to a thermal cycle of -65 ° C to + 150 ° C for 2000 cycles.
No delamination occurs at the joints, and there is no measurable decrease in adhesive bonding.
Was not.       [0097]   As shown in FIG. 8, a bump of a flexible conductive adhesive 140 and an insulating flexible contact are formed on the upper part.
The prepared semiconductor device 130 having the pattern of the adhesive 150 is the next level.
Is mounted on the substrate, that is, the substrate 120, and as shown in FIG.
The device 100 is formed. The semiconductor device 130 includes a substrate 120 and a semiconductor device.
The substrate is positioned such that the respective contact pads 124, 134 of 130 are aligned.
120 are aligned.       [0098]   The device 130 and the substrate 120 are pressed together and the temperature is in the range of 195 to 215 ° C.
And at an installation pressure of about 10 psi, the flexible adhesive bump 140
The respective contact pads 124 and 134 are instantaneously joined together. In a similar way,
Insulating flexible adhesive 150 halves the area between contact pads 124 of substrate 120.
Bonded to the corresponding area between the contact pads 134 of the conductive device 130.       [0099]   To be more efficient, the substrate 120 can be pre-heated to a temperature of about 150-200 ° C.
While heated, the chuck that picks up the semiconductor chip 130 is about 220
Preheated to ~ 280 ° C. Joined on the alumina substrate 120 and the edge size is 10
Electronic device 10 as described above, including semiconductor die 130 of greater than 10 mm
0 is greater than 1000 thermal cycles between -65 ° C and + 150 ° C;
It is resistant to exceeding 50 temperature shock between -150 ° C and measurable contact resistance change.
It is known that there is no conversion.       [0100]   Electrical contact resistance after exposure to 85 ° C. at 85% relative humidity (RH) for 168 hours
No measurable degradation at all, and 1 hour at 100% RH for 200 hours.
Can measure the shear bond strength of die 130 to substrate 120 even when exposed to 00 ° C
No effective deterioration was observed. Thick and thin gold bonding pads on alumina substrate
It was shown to be satisfactory.       [0101]   The assembly process is similar to when a flexible epoxy adhesive is used.
The placement chuck is maintained at a low temperature of 150-175 ° C and is the next level plate
The die to be placed on the plate can be used without any pressure or other equipment prior to assembly.
Cure at 50-175 ° C for an additional 5 minutes. Thermoplastic flexible adhesive is used
The temperature of the placement chuck (and the temperature of the die it holds)
The temperature is controlled by the conductive bumps of the flexible adhesive and the underfill of the insulating adhesive, if any.
Must be maintained at a temperature several degrees higher than the temperature at which it can flow.       [0102]   For most applications, the size of the contact pads 34 and the adhesive bumps 40 will be
It may be the same. However, the number of contact pads was relatively small.
Therefore, since the entire bonding area becomes relatively narrow, the pitch of the contact pads
That is, while maintaining the distance between centers between adjacent contact pads),
Advantages of making the area of the conductive bumps substantially larger than the area of the contact pads
In some cases,       [0103]   As described above, when the area of the flexible conductive bump is increased, the semiconductor device 30
Mechanical strength between the substrate and the substrate 20 is increased, the total electrical resistance is reduced,
Have a higher ability to pass current through the conductive interconnect.       [0104]   The dense area of the contact pad 34 is about 3% of the entire area of the semiconductor device 30.
Substantially less than 3%, sufficient bonding strength in the joint area without reinforcement
May not be given.       [0105]   In the embodiment of FIG. 9, a bump of flexible conductive adhesive on the semiconductor device 30 is shown.
The step 240 covers an area substantially larger than the area of the individual bonding pads 34.
It is expanding intentionally. The enlarged conductive adhesive bump 240 is closest to
Used while maintaining the recommended minimum spacing between pads is greater than 50 micrometers
When the conductive bump 240 is "overhanged,"
The area is increased to more than about 50%, and even without the use of an underfill layer,
The integrity of the joint may be increased by using only the conductive adhesive.       [0106]   On the other hand, the number of the contact pads 34 is large, and the pitch of the contact pads is narrow.
If so, substantially reduce the area of the flexible conductive bumps while maintaining that pitch.
May be desirable. Thus, the area of the conductive bumps can be reduced.
Reduces the possibility of bridging between adjacent interconnects during the bonding process
Reduce. Reducing the area of the flexible interconnect requires the use of an insulating underfill.
Especially useful if not.       [0107]   For example, contact pads 34 are closer together than about 100 micrometers.
In this case, a conductive bump 340 having a smaller area than the contact pad 34 is used.
May be. In FIG. 10, the region of the conductive bump 340 is the semiconductor device 3
0 is substantially smaller than the area of the bonding pad 34. This approach is
It is more suitable for low current density interconnects, where the substrate 20 and the semiconductor device 30 are integrated.
The electronic circuitry forming the part allows higher interconnect resistance to be tolerated.       [0108]   The invention has been described with reference to the following exemplary embodiments, which are defined by the claims.
Variations within the scope and spirit of the invention will be apparent to those skilled in the art.       [0109]   For example, the material of the circuit board of the substrate 20 is ceramic having a CTE of 7 ppm / ° C.
It may be different from alumina. In fact, for most industrial applications,
FR-4, BT and other organic substrate materials have been used,
The CTE is 3 ppm / ° C between the silicon flip chip and the substrate.
The degree of inconsistency of CTE is from 17 ppm / ° C CTE of alumina to 17 pp of FR-4.
increase to m / ° C CTE. The higher the CTE mismatch, for example, 1
Higher than 0 ppm / ° C, interconnects due to thermal cycling and thermal shock
Is more likely to occur due to delamination or breakage.       [0110]   Bonded to aluminum substrate so that CTE mismatch is 3: 25ppm / ℃
AI Technology, including a silicon device with a 16 mm rim dimension
y, Inc. Conductive adhesive LTP8150 and ESS84 available from
In the electronic device 10 according to the present invention assembled by using the 50 type, 2000
Thermal cycle from -65 ° C to 150 ° C, which exceeds the cycle, can detect detectable delamination
No change in adhesive strength was observed. For electronic devices using FR-4 substrate
As a result of the same test, no delamination or change in adhesive strength was observed
Was.       [0111]   In addition, the same or similar to AI Technology type LTP8150
Other flexible conductive adhesives having the flexibility, adhesion and conductivity of the isolated molecules;
They may be replaced with flexible adhesives using other conductive fillers.       [0112]   Stencil, screening, masking, inkjet printing, contour
Alternative and appropriate deposition methods, such as object deposition, preform lamination, and needle delivery
Used to provide conductive pads to the contact pads of the semiconductor 30 or other electronic components 44, 46
Adhesive bumps 40, 140, 240 may be deposited, or
Conductive adhesive bumps 40, 140, 240 are deposited on contact pads of plate 20
You may let it.       [0113]   The exemplary embodiment described above relates to a flexible conductive adhesive bump and a flexible insulating adhesive.
Both of the patterns were to be deposited on the semiconductor die, but the flexible conductive adhesive
Note that the bumps and flexible insulating adhesive pattern may be deposited on the substrate.
I want to be.       [0114]   Instead, a pattern of flexible insulating adhesive is applied to the semiconductor device or substrate.
It may be deposited on any one, and furthermore, a bump of flexible conductive adhesive may be
It may be deposited on another of them. In addition, the flexible insulating adhesive
Filling may be performed in a conductive state but not an insulating filler.       [0115]   Such suitable adhesives include AI Technology, Inc. Enter from
LESP7455, LESP7555, LTP7555 and L
Including TP7095 type.       [0116]   The above exemplary embodiments are shown with respect to a single flip chip installation.
However, using the method described in the present specification, a large number of semiconductor chips are formed on the same substrate.
Obviously, it may be mounted. Also bear (ie coated
Not) both flip-chip semiconductor devices and other electronic components, and even packages
Conductive semiconductor bumps described in the present specification.
Note that it may be mounted on the same circuit board using the method described above. [Brief description of the drawings]     FIG.   1 illustrates an embodiment of an electronic device including a flip-chip semiconductor device according to the present invention.
It is sectional drawing.     FIG. 2   3 is a graph showing the elastic modulus of various adhesives as a function of temperature.     FIG. 3   FIG. 2 is a plan view illustrating a semiconductor device used in the embodiment of FIG. 1.     FIG. 4   FIG. 4 is a cross-sectional view showing the semiconductor device of FIG. 3 before applying a flexible conductive adhesive.
You.     FIG. 5   FIG. 4 is a cross-sectional view showing the semiconductor device of FIG. 3 after applying a flexible conductive adhesive.
You.     FIG. 6   An alternative embodiment of an electronic device comprising a flip-chip semiconductor device according to the invention
FIG.     FIG. 7   FIG. 7 is a plan view illustrating a semiconductor device used in the embodiment of FIG. 6.     FIG. 8   7 after application of a flexible conductive adhesive and a flexible underfill
It is sectional drawing which shows a device.     FIG. 9   4 and 7 after application of a flexible conductive adhesive.
FIG. 4 is a cross-sectional view illustrating an alternative embodiment.     FIG. 10   4 and 7 after application of a flexible conductive adhesive.
FIG. 4 is a cross-sectional view illustrating an alternative embodiment.

────────────────────────────────────────────────── ─── Continuation of front page    (31) Priority claim number 60 / 092,147 (32) Priority Date July 9, 1998 (July 9, 1998) (33) Priority country United States (US) (31) Priority claim number 09 / 166,633 (32) Priority date October 5, 1998 (1998.10.5) (33) Priority country United States (US) (31) Priority claim number 09 / 276,259 (32) Priority date March 25, 1999 (March 25, 1999) (33) Priority country United States (US) (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), CN, JP, K R, SG, US F term (reference) 5E319 AA03 AB05 AC01 AC16 BB11                       CC61 CD26 GG11                 5E336 AA04 BB01 BB02 BB03 CC32                       CC36 CC44 CC55 EE08 GG09                       GG14 GG16                 5F044 LL07 [Continuation of summary] Metal, preferably noble metal, before internal connection to prevent Preferably, it is protected by a neutral coating (38). Flexible Insulating organic underfill (150) may be used In addition, the elastic modulus of the flexible conductive adhesive (40, 14 Preferably substantially as low as 0) No.

Claims (1)

Claims 1. At least one semiconductor device (30, 130) having a plurality of contact pads (34, 134) on a first surface thereof; and a substrate (20). , 120) having a first surface with a plurality of contact pads (
24, 124), the contact pads (24, 124) of the substrate (20, 120) are arranged in a pattern corresponding to the contact pads (34, 134) on the semiconductor device (20, 120). The semiconductor device (
30, 130) and a substrate configured to arrange the first surfaces of the respective substrates (20, 120) close to each other; and contact pads (34, 134) of the semiconductor substrate (30, 130). And a plurality of flexible conductive adhesive connections (40, 140) between each one of the contact pads (24, 124) of the substrate (20, 120), The electronic device (10, 100), wherein the elastic modulus of the flexible conductive adhesive is lower than 35,000 kg / cm ² .