JP2000044922A - Photocurable composition containing flux activator containing active hydrogen and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process to inexpensively prepare within few minutes a precise alignment of hundred-thousands of electrical contacts covering the entire surface of a 12 inch (30.48 cm)-wafer for preparing a flip chip. SOLUTION: A photocurable composition has an adhesive strength of at least 0.5 g/mm2 and contains a flux activator containing at least one active hydrogen chosen from the group consisting of alkanolamines, monobasic acids, hydroxy acids, hydroxy acid salts, hydroxy acid derivatives and mixtures thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photocurable element for use in preparing a precise array of conductive bumps on an electronic substrate. More particularly, the present invention relates to a photocurable composition comprising a flux activator containing active hydrogen.

[0002]

BACKGROUND OF THE INVENTION Higher density integrated circuits (ICs) having an increasing number of electrical contacts to external circuits (I / Os).
There is a trend in the industry toward (type). The best distribution of I / Os is not at the perimeter as dictated by the old practice of wire bonding the IC to external circuits, but rather across the entire surface of the IC. is there. What is needed is a quick and inexpensive way to emit a controlled amount of conductors, such as solder, for I / O anywhere on the IC surface. Next, the solder forms the necessary connections to the external circuit.

[0003] One method of emitting a controlled amount of electrical conductor to a substrate is by immersing a metal plate containing a plurality of holes corresponding to the desired emission locations into solder particles (a robotic sphere). Placement (robotics sphere placeme
nt)). However, when a design change using a particle size of less than about 10 mils is required, and at the same time the number of particles to be released separately to a particular location is one I
This technology is too slow when it exceeds a few hundred per C,
And too expensive.

Another method of releasing a controlled amount of conductor to a substrate is metal plating. However, this method is slow, capital intensive, and generates toxic waste.

Another method of releasing a controlled amount of conductor onto a substrate is screen printing of a solder paste. However, this method does not provide the resolution and bump conductivity required for "state of the art" IC fabrication.

[0006]

SUMMARY OF THE INVENTION On the surface of an electronic substrate,
At a pitch of 0.003 inches (0.00762 cm),
There remains a need for photocurable elements for use in preparing precise arrays of conductive bumps that can release 0.005 inch (0.0127 cm) conductive bumps inexpensively and within minutes. I do. Industry trends are, for example, about 0.002 inches (0.005c).
m) towards smaller sizes.

[0007]

The present invention is selected from the group consisting of alkanolamines, monobasic and polybasic acids, hydroxy acids, salts of hydroxy acids, hydroxy acid derivatives, and mixtures thereof. Flux activator containing at least one active hydrogen (flux ac
tivator) and has a tackiness of at least 0.5 gram / mm ² . Preferably,
As the photocurable composition has a 2-6 g / mm ² tacky. Tackiness is measured by Chatillo as in the IPC-TM-650 Test Method Manual, number 2.4.44.
n Measured using Tack Tester. Typically, the photocurable compositions of the present invention may further comprise, in addition to the active hydrogen-containing flux activator, an ethylenically unsaturated compound, a polymeric binder, and an initiator or initiator system. .

In another embodiment of the present invention, a method for forming a fine array of conductive bumps on a permanent substrate includes the steps of: (a) sensitizing a permanent substrate to a flexible substrate. Providing a photosensitive layer on a permanent substrate, either by laminating a photosensitive element containing the photosensitive layer, or by applying or spraying the photosensitive layer on a permanent substrate. The photosensitive layer may be an alkanolamine,
Comprising a flux activator containing an active hydrogen, which may be selected from the group consisting of monobasic and polybasic acids, hydroxy acids, salts of hydroxy acids, derivatives of hydroxy acids, and mixtures thereof; (B) before or after step (a), exposing said photosensitive layer to actinic radiation to form tacky and non-tacky areas within said photosensitive layer; (c) if present Stripping the flexible substrate and contacting the tacky areas of the photosensitive layer with conductive and free-flowing particles, such as solder balls, to form an array; Heating the array containing the photosensitive element to melt the conductive particles and form a conductive bond on the permanent substrate.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention provides several advantages over the prior art described above. The present invention provides an inexpensive and fast method for flip chip production that was previously unavailable. The present invention uses a 12 inch (3
0.48 cm), making it possible to produce a precise array of potentially hundreds of thousands of electrical contacts over the entire wafer at low cost and within minutes.

[0010] The present invention provides a method for producing at least one active hydrogen selected from the group consisting of alkanolamines, monobasic and polybasic acids, hydroxy acids, salts of hydroxy acids, hydroxy acid derivatives, and mixtures thereof. A flux activator containing at least 0.5
A photocurable composition having a gram / mm ² tackiness is provided. Preferably, the photocurable composition has a tackiness of ^{2 to} 6 grams / mm2. Adhesion is IPC-TM
Measured using the Chatillon Tack Tester, as in the -650 Test Method Manual, number 2.4.44. Typically, in addition to the flux activator containing active hydrogen, the photocurable composition of the present invention may further comprise an ethylenically unsaturated compound, a polymeric binder, and an initiator or initiator system. . Some useful photocurable elements are described in U.S. Pat. No. 3,649,268, U.S. Pat. No. 3,854,950, U.S. Pat. No. 4,174,216.
No. 4,282,308; U.S. Pat.
No. 948,704, and US Pat. No. 5,001,03.
No. 7, the disclosures of which are hereby incorporated by reference.

The photocurable composition is generally a combination of a polymeric binder, a photopolymerizable monomer, and an initiator or initiator system. Some suitable binders are
Linear polymers and / or copolymers, such as polymethyl methacrylate, poly-n-butyl methacrylate, polyvinyl acetate, (methyl methacrylate / methacrylic acid) copolymer, and (methyl vinyl ether / monoethyl maleate) Ester) copolymers, each of which may be copolymerized in various ratios. Some suitable photocurable monomers are disclosed in U.S. Pat.
And ethylenically unsaturated monomers such as those disclosed in U.S. Pat. No. 0,863, U.S. Pat. No. 3,380,831, and U.S. Pat. No. 3,573,918.
Some examples include dipentaerythritol acrylate (50% tetra and 50% penta), pentaerythritol triacrylate and tetraacrylate, pentaerythritol tetramethacrylate, polypropylene glycol (number average molecular weight 425) dimethacrylate, trimethylolpropane triacrylate,
Diacrylates of resins derived from bisphenol A and epichlorohydrin, triacrylates of ethoxylated trimethylolpropane resins, triacrylates of ethoxylated pentaerythritol,
α, ω-alkanediol diacrylates, diethylene glycol diacrylate, triethylene glycol diacrylate, urethane diacrylates, urethane triacrylates, urethane dimethacrylates,
Urethane trimethacrylates, glyceryl dimethacrylate, dimethacrylates of resins derived from bisphenol A and epichlorohydrin, triacrylates of resins derived from styrene and maleic anhydride, trimethacrylates of resins derived from styrene and maleic anhydride, And dimethacrylates of α, ω-alkanediols. Also useful are epoxy monomers containing ethylenic unsaturation, for example, monomers of that type are described in US Pat.
1,576 and British Patent 1,006,587.

The concentration of the binder may vary, but is generally limited to smaller values that allow the molten solder to penetrate to the underlying final substrate. Excessively high binder concentrations can prevent the final substrate from bonding (wetting) with the solder. The presence of a binder is responsible for the formation of stickiness, rheological control of the solution, cohesion of the layers, and possible compatibility with the components of another photosensitive layer. The higher the molecular weight, the lower the concentration of the polymer used in the present invention, for example, 10,000
Polymers having a molecular weight of more than 10% are preferably used in the present invention in a concentration range of less than 10% by weight, based on the dry weight of the layer components. 1,000 to 10,000
For polymers having a molecular weight of up to 00, a useful concentration range is 30% by weight, based on the dry weight of the layer components.
Up to. As used herein, "dry weight of layer components" means the total weight of components excluding the solvent in the coating solution of the photosensitive layer, that is, the total weight of non-volatile components.

The monomers must be compatible with the binder and may be solvents for the binder and / or have a plasticizing effect on the binder. According to the requirements of selective light patterning, the choice of monomers and binders is made and the ratios are determined. Useful monomer concentrations will vary according to the molecular weight of the binder, the concentration of the binder, and the compatibility of the monomer with the binder. The monomer concentration is usually in the range of about 20-50% by weight, preferably 30-45% by weight, based on the dry weight of the layer components.

The components of the photosensitive layer can flow or dissipate while the solder is reflowing, and for good metal-to-metal bonding, the final substrate with the molten solder underneath. It must be possible to reach the surface. Ingredients useful in this regard are Hercules, Inc.
Low molecular weight rosin derivatives, such as FORAL AX, sold by US Pat. No. 5,344,592 and US Pat. No. 5,397,383 based on α-methylstyrene. . Useful concentrations of such components are up to about 50% by weight, based on the dry weight of the layer components.

Suitable free radical generating and addition polymerizable initiators or initiator systems are disclosed in US Pat.
No. 752, US Pat. No. 3,060,023, US Pat. No. 3,549,367, US Pat. No. 3,558,32
No. 2, U.S. Pat. No. 3,926,643, and U.S. Pat. No. 3,615,454, the disclosures of which are incorporated herein by reference. When a standard initiator or initiator system, such as benzophenone, is used in combination with the sensitizer and chain transfer agent, the initiator or initiator system may be 3-20% by weight, based on the dry weight of the layer components. May be present.

It has been found that certain alkanolamine flux activators have a tendency to inhibit photopolymerization reactions which result in the formation of the sticky point pattern required in imaging. In such a situation,
Concentrations higher than those of conventional initiators or initiator systems are used, with a range as high as 8-20% by weight.
In these circumstances, the concentration of the alkanolamine is preferably maintained at a low value, ie, at least less than about 12% by weight, based on the dry weight of the layer components. The photosensitive layer may similarly contain a component containing a plasticizer, an antihalation agent, and a fluorescent whitening agent.

When the pattern of sticky areas is not used immediately, ie when stored or transported,
It is useful to protect those sticky areas and keep them clean with cover sheets such as polyester films, polypropylene films, polyethylene films. Generally, 0.0127 mm (0.0005 inch) thin
Mylar® polyester film (EI du
Pont de Nemours and Company, Inc., Wilmington, DE)
Is enough.

Flux activator containing active hydrogen The desired photoimageable layer must have a particular combination of properties. This material exhibits very different tackiness (ability to stick to conductive and free-flowing particles, such as solder balls) before and after imagewise exposure to actinic radiation (eg, ultraviolet light). There must be. Such imagewise exposure must be capable of forming a pattern of multiple sticky spots (dots) in a non-sticky background (at the surface of the photoimageable material). Each of the tacky areas exhibits sufficient tackiness to form at least one conductive and free-flowing particle (eg, a solder ball), preferably one conductive and free-flowing particle. Must be held until the solder melts (reflows). The photoimageable material is apparently flowable or dissipates during reflow and, for good metal-to-metal bonding, molten conductive and free-flowing particles (eg, solder) Must be able to reach the metallized surface (initially under the photoimageable material).

The flux activator associated with the components of the photosensitive layer is used to melt the conductive and free-flowing particles (eg, solder spheres) in order to improve the degree of final metal bonding (wetting). Before this occurs, it must be possible to clean the surface of the conductive and free-flowing particles such as solder balls and the surface of the underlying metallization.

Typically, the flux activator is diethanolamine, triethanolamine, N-benzylethanolamine, α-hydroxymethyl-pyridine,
Alkanolamines such as 2- (2-aminoethylamino) ethanol, diglycolamine, and N-hydroxyethyl-ethylenediamine; acetic acid, formic acid, benzoic acid, palmitic acid, adipic acid, malonic acid, substituted malonic acid And monobasic and polybasic acids such as succinic acid and glutaric acid; hydroxy acids such as hydroxyacetic acid, lactic acid, citric acid, salts and derivatives thereof; and mixtures thereof. . Particularly preferred flux activators include malonic acid, alkanolamines and mixtures thereof.

Certain flux activators have been found to inhibit normal polymerization reactions. When using these flux activators, it is necessary to increase the amount of initiator above normal levels to obtain the desired patterning in the imaging process. The flux activator is 2% based on the dry weight of the layer components.
It may be present in an amount up to 5% by weight, preferably 1-20% by weight.

Permanent Substrate The choice of substrate is highly dependent on the method chosen to attach the array of particles to the contact pads. However, generally speaking, the substrate must be stable, smooth, and preferably exhibit good adhesion to the photosensitive composition under the conditions of the intended application. Because the substrate can be heated with an array of conductive and free-flowing particles, the substrate is heated to the temperature used to melt the array of particles (eg, solder balls) to form conductive bumps. Must be able to withstand.
Some suitable substrates are, for example, EI du Pont de N
Including organic polymer films, such as Kapton® polyimide films available from emours and Company, Inc., ceramics, dielectrics, quartz, glass, or semiconductors such as silicon wafers. Suitable substrates may also include metals wired to the aforementioned substrates. These permanent substrates are provided with metal contact pads on which solder bumps are to be formed. Preferably, the permanent substrate is an IC wafer having contact pads thereon. As will be appreciated by those skilled in the art, one or more intermediate layers may be applied to the substrate to prevent sticking of the photosensitive layer, as long as the intermediate layers do not interfere with the wetting of the permanent substrate during reflow. May be improved.

Process (a) laminating a photosensitive element comprising a photosensitive layer on a flexible substrate to a permanent substrate, or applying the photosensitive layer directly on a permanent substrate; or Providing, by either spraying, a photosensitive layer having a tackiness of at least 0.5 grams / mm ² on a permanent substrate, said photosensitive layer comprising diethanolamine, triethanolamine, N-benzylethanolamine, α-hydroxymethyl-pyridine, 2- (2-aminoethylamino) ethanol, diglycolamine,
And alkanolamines such as N-hydroxyethyl-ethylenediamine; monobasic and polybasic such as acetic acid, formic acid, benzoic acid, palmitic acid, adipic acid, malonic acid, substituted malonic acid, succinic acid and glutaric acid A step selected from the group consisting of hydroxy acids, such as hydroxyacetic acid, lactic acid, citric acid, salts thereof and derivatives thereof; and mixtures thereof; (b) prior to step (a), Or later exposing said photosensitive layer to actinic radiation to form tacky and non-tacky areas within said photosensitive layer; and (c) stripping said flexible substrate, if present. Contacting the tacky areas of the photosensitive layer with conductive and free-flowing particles (eg, solder balls) to form an array; Heating the array containing the photosensitive element to melt the conductive particles to form a conductive bond to the permanent substrate. Process for forming an array.

As used herein, the term "sticky area" refers to an area that has an adhesive property, the adhesive property of which is:
When in contact with conductive and free-flowing particles such as solder spheres, the bond is immediately formed by the effect of the weight of the particles. In a preferred embodiment, the tacky area must have a size and bond strength appropriate for the sticking of at least one free-flowing particle (eg, a solder ball). Preferably, the tacky area is 1
It has dimensions and bond strength appropriate for the adhesion of two solder balls or free-flowing particles. Typically, the tacky area is smaller than the average particle size. The shape of the sticky area is circle, square, rectangle, polygon, ellipse, star, cross hatch,
Mixtures thereof, or other shapes that facilitate retention of the particles, may be used. Generally, a circular tacky area is preferred.

In one embodiment, when the photosensitive composition is used to create an array of tacky and non-tacky areas, the photosensitive composition is first placed on a suitable permanent substrate. , Sprayed or painted, and then imagewise exposed to create the desired sequence of tacky and non-tacky. In another embodiment,
The photosensitive composition may be sprayed or spread on a temporary substrate and dried to provide a layer of a predetermined thickness. The layers on the temporary substrate can be laminated on a permanent substrate and then exposed to form an image. This temporary substrate must be stable under the conditions of the intended application, smooth and exhibit good adhesion to the photosensitive composition. Suitable temporary substrates include flexible polyester films, such as Mylar® polyester film from DuPont.

In the above-described photosensitive product, the array pattern is first constructed by manual or computer-aided design and is transferred to photographic film, which is usually used as a light tool in contact with the photosensitive product. Exposure to actinic radiation is performed through a light tool to form a pattern of sticky and non-sticky areas in the photosensitive product. Another patterning method involves direct writing as in digital imaging using projection exposure and a laser output device.

If present, the flexible substrate (ie, the temporary substrate) is stripped off, and the sticky areas of the photosensitive layer are contacted with free-flowing particles (eg, solder balls) to form an array. Form. The particles effectively and accurately stick to the sticky areas of the surface containing an array of sticky and non-sticky areas, and the particles are removed from the non-sticky areas without removing the particles from the sticky areas This is very important.

In most electronic applications, conductive and free-flowing particles for use in the present invention include copper,
Includes indium, lead, tin, gold, and their alloys.
Most preferred are solder balls. However, it will be apparent to one skilled in the art that the type of particles used in conjunction with the present invention is dictated by the particular application, and is not an inherent limitation of the present invention. For example, certain applications may require solder bumps on the contact pads, for example, to separate one contact pad in a stack of circuit boards from another. The present invention can also be used to advantage in such an environment. Generally speaking, in the practice of the present invention, spherical particles are preferred due to their ease of handling and particle symmetry. However, it should be understood that the size and shape of the particles are not critical to the invention.

The step of accurately and effectively adhering the free-flowing particles to the tacky area can be performed in a number of ways. Generally, an article having a pattern of sticky areas is placed in a container with an excess of particles that are moved across the array until all sticky areas are occupied. Alternatively, sprinkle excess particles until all tacky areas are covered with particles. Excess particles are
By gravity, gently dabbing, gently blowing, decompression and other methods, the pattern is completely removed from the occupied sticky area. The force used to clean excess particles depends on the adhesion of the bond between the tacky area and the particles. The use of ion generators, such as in conductively grounded containers, humidified atmospheres, and the use of ionized air, prevents electrostatic charging when used to pattern electrostatic areas. The adhesion of the flowable particles is best performed. This step is
The clean atmosphere further assists in preventing foreign matter from adhering to the sticky areas. Typically, the particles first adhere to the tacky area at the periphery of the tacky area due to relatively little wetting of the particles by the tacky area. Thereafter, in equilibrium wetting, complete or nearly complete embedding of the particles in the tacky area typically takes place by centering the particles.

The process of attaching the particles to the pattern of tacky areas is assisted by the tacky areas having sufficient tackiness to trap and retain the particles upon contact. The adhesion of the particles to the sticky area is
Further, it must be strong enough to withstand various forces (eg, vibrators, tapping, shaking, jolting, moving, impact contact, depressurizing or blowing). Is desired. In addition, it is advantageous to have sufficient adhesive strength between the particles and the tacky area to hold the particles in place during handling and possible transport. Furthermore, the tacky area should have a tackiness of at least 0.5 gram / mm ² , especially when the pattern of sticky areas in which the particles are distributed is transported without loss of particles.

The location of the tacky area is sufficiently close to the underlying contact pad that the molten conductive and free-flowing particles from the initially deposited conductive and free-flowing particles (eg, Molten solder) must be able to contact some part of the contact pad to which it is to be applied. After the particles (eg, solder balls) have been melted, it is necessary to make direct contact between the molten particles and the pad, so that the molten particles wet the pad and end to end of the metal surface. To cover the metalized pad. The initial placement of the particles on the metallized pad may be off-center or non-contact. This is because the wetting action of the molten particles moves the particles to the center on the pad during deposition. However, care must be taken to prevent particles on adjacent tacky areas from contacting before and during application to the contact pads to avoid bridging adjacent contact pads. Typically, for a tacky area having a particular size and bond strength, there is an upper limit on the size and weight of the particle above which there is substantially no tackiness of the particle, and adheres alone to each tacky area There is a lower limit on particle size. For example, a tacky area with a tack of 2-6 grams / mm ² and 0.127-0.726 mm
For particles with a diameter of (0.005 to 0.030 inches), the tacky area can be as small as 15% of the particle size to as large as 100% of the particle size and still one One deposition of particles per sticky area is obtained. A tacky area of at least 30% of the particle size is preferred.
More preferably, a tacky area of 45-60% of the particle size is preferred. The size of the tacky area is preferably the size of the IO pad containing the photocured material outside the boundaries of the IO pad. This results in maximum wetting of the IO pad during the process.

Next, the array of free-flowing particles (eg, solder balls) on the tacky areas of the photosensitive element is melted to form a conductive bond to the permanent substrate. The heat required to melt the particles may be provided by an oven, laser, microwave, infrared, or another conventional method. Fifteen
Temperatures in the range from 0 ° C. to 400 ° C. are usually sufficient to cause reflow of the particles, especially the solder spheres. It will be apparent to those skilled in the art that a permanent substrate is heated together, so that the substrate must withstand such temperatures. In the case where the heat source used does not heat the substrate or sensitive and insensitive areas (eg a laser), thermal stability is not a major concern. It is critical that the molten particles separate or displace the sticky areas on the contact pads and completely wet the contact pads with the molten particles (eg, solder). This can be done by decomposing the sticky area into volatile compounds when the melting temperature of the particles is reached, or by using a thermally stable sticky area material that can be replaced by molten particles. it can. Next, the molten particles are allowed to cool and re-solidify on the contact pads to form conductive bumps (eg, solder bumps).

[0033]

The present invention is further illustrated by the following examples, which do not limit the invention. Parts and percentages are by weight unless otherwise indicated.

Example 1 The following solutions were mixed. All except Coating Solution C are 92DP Mylar® films (EI duPont de Nemours and Company,
Inc., Wilmington, DE), 2 mils wet
(50.8 μm). Coating solution C was not coated because it showed a large amount of white precipitate. A polypropylene film coversheet was applied over the dried coating. The coating solution had the following components:

[0035]

[Table 1]

The cover sheet of each coating was removed from the above example, and each coating was laminated on a copper substrate.
Each of the stacked samples was placed on a non-sticky background for 25
Six 9 mil (228.6 μm) sticky dots [5
0 mil (1270 μm) pitch]. Next, 92 DPM
The ylar® film was removed and the imaged coating was flooded with 20 mil (508 μm) diameter solder balls. Excess was rolled off the surface of the imaged coating. The number of spheres sticking at this stage was recorded as a percent population. The occupied sample was reduced to 2
Heating to 30 ° C. melted the solder balls. The solder joints ("bumps") were visually inspected and the extent of bonding (wetting) was assessed.

The appearance of the coating can be used as a rough measure of rheology. In this case, the haze is
It shows phase separation, ie poor compatibility of the components. Systems with good compatibility are transparent. Fatty (greasiness)
It simply exhibits excessive plasticization due to phase separation and / or liquid components. The appearance of an "orange peel" indicates poor film-forming composition and / or poor wetting of the film base.

The results are shown in Table 5 below.

Example 2 The following solution was prepared and then coated 2 mil (50.8 μm) wet on a 92DP Mylar® film. A polypropylene film cover sheet was provided on the dried coating. The coating solution had the following components:

[0040]

[Table 2]

The samples were tested as described in Example 1. The results are shown in Table 5 below.

Example 3 The following solution was made and then 1 mil (25.4 μm) and 2 mil (5 mil) wet on a 92DP Mylar® film.
0.8 μm). A polypropylene film cover sheet was provided on the dried coating. The coating solution had the following components:

[0043]

[Table 3]

The samples were tested as described in Example 1. The results are shown in Table 5 below.

Example 4 The following solutions were mixed. Coating solution A was not coated because it showed a large amount of precipitate. Coating solution B and C were added to 92DP Mylar
1 mil (25.
4 μm) and 2 mils (50.8 μm). A polypropylene film cover sheet was provided on the dried coating. The coating solution had the following components:

[0046]

[Table 4]

The samples were tested as described in Example 1. The results are shown in Table 5 below.

[0048]

[Table 5]

Sample 1A shows that a flux activator is desirable to obtain good metal-to-metal bonding (wetting) during reflow. However, for example, sample 1B,
If, as in 1C, 2C, they crystallize or otherwise phase separate, and the activating component is incompatible with the rest of the component, non-wetting may still occur. is there. When using a binder with a molecular weight that is too large, the presence of the flux activator may be insufficient for good wetting. The best results were obtained with the coating having the highest overall component compatibility. For Sample 2E, the photosensitive or photopolymer layer was removed with a disposable substrate after reverse lamination to a permanent substrate (reverse adhesion). Example 2D shows superior performance compared to 2F without flux activator.

Example 5 The following solutions were mixed and then coated 2 mil (50.8 μm) wet on a 92DP Mylar® film. The dried coating was provided with a coversheet using polypropylene.

[0051]

[Table 6]

Test Results These coatings were tested as in Example 1.

[0053]

[Table 7]

In the table, ¹ indicates that the molten solder has flowed across the entire surface of the final substrate.

[0055]

According to the present invention, 12 inches (30.48 c
m), which allows a precise arrangement of potentially hundreds of thousands of electrical contacts to be produced inexpensively and within a few minutes, spread over the entire wafer. Therefore, by using the present invention, a flip chip can be manufactured inexpensively and quickly.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Alan Kairuncross United States 19707 Hockesin Cinnamon Drive, Delaware 24 (72) Inventor Ronald John Converse United States 18848 Pennsylvania Towanda Patterson Boulevard (No Address) E.I. Within Dupont de Nemours & Company (72) Inventor Daphne Pinto Fix United States 19348 Kennett Square West, Pennsylvania. Locust Lane 325 (72) Inventor Michael Aaron Saltsburg United States 19072 Navers, PA PA Maple Avenue 108

Claims (7)

[Claims] 1. A photocurable composition having a tackiness of at least 0.5 gram / mm ² , comprising alkanolamines, monobasic and polybasic acids, hydroxy acids,
A photocurable composition comprising a flux activator containing at least one active hydrogen selected from the group consisting of hydroxy acid salts, hydroxy acid derivatives, and mixtures thereof. 2. The alkanolamine is diethanolamine, triethanolamine, N-benzylethanolamine, α-hydroxymethyl-pyridine, 2-alkanolamine.
(2-aminoethylamino) ethanol, diglycolamine, and N-hydroxyethyl-ethylenediamine; the monobasic and polybasic acids are acetic acid, malonic acid, substituted malonic acid, succinic acid. The hydroxy acid is selected from the group consisting of hydroxy acid salts, hydroxyacetic acid, lactic acid, and citric acid; and the flux activator is based on the dry weight of the layer components Photocurable composition according to claim 1, characterized in that it is present in an amount of up to 25% by weight. 3. Photocuring according to claim 1, further comprising the ethylenically unsaturated compound in an amount of from 20 to 50% by weight, based on the dry weight of the layer components. Composition. 4. The composition according to claim 1, wherein the dry weight of the layer components is from 1 to 3
The photocurable composition according to claim 1, further comprising at least one polymer binder in an amount of 0% by weight. 5. The composition of claim 1, further comprising an initiator or initiator system capable of generating free radicals, wherein said initiator or initiator system is from 3 to 2 based on the dry weight of the layer components.
2. The photocurable composition according to claim 1, wherein it is present in an amount of 0% by weight. 6. A method for forming a fine array of conductive bumps on a permanent substrate, comprising: a) forming a photosensitive element comprising a photosensitive layer on a flexible substrate relative to the permanent substrate. A photosensitive layer having a tackiness of at least 0.5 grams / mm ² is deposited on a permanent substrate, either by laminating or by applying or spraying the photosensitive layer on a permanent substrate. Providing, wherein the photosensitive layer comprises a flux activator containing active hydrogen; and b) before or after step a), the image of the photosensitive layer is exposed to actinic radiation. Exposing the flexible substrate, if present, to form tacky and non-tacky areas in the photosensitive layer;
Contacting the tacky areas of the photosensitive layer with conductive and free-flowing particles to form an array; and d) removing the array containing the photosensitive element formed by step c). Heating to melt the particles and form a conductive bond on the permanent substrate. 7. The method of claim 6, wherein the conductive and free-flowing particles are solder spheres.