A bottom filling adhesive with reworkability, preparation method and application thereof

Abstract

The present invention discloses a bottom filling adhesive with reworkability, a preparation method and application thereof. The bottom filling adhesive, with the total weight being 100%, comprises: 25-35% inorganic filler, 12-14% modified isosorbide-based epoxy resin, 13-16% bisphenol F-type epoxy resin, 13-20% polyether modified epoxy resin, 12-20% curing agent, 8-16% epoxy diluent, 0.2-0.4% accelerator, and 0.1-0.2% pigment. The bottom filling adhesive of the present application has excellent fluidity, flexibility and reworkability; when used for bottom filling of BGA chips or CSP chips, its excellent reworkability helps to reduce maintenance costs and shorten maintenance time.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor chip bottom filling glue, and in particular to a bottom filling glue with reworkability, a preparation method thereof and an application thereof. Background Art

[0002] The bottom filler mainly includes epoxy resin and inorganic filler, which is used to fill the bottom of the chip in BGA and CSP packaging mode. After heating and curing, a filling layer is formed to fill the gap at the bottom of the chip. The bottom filler is used to seal and protect circuit boards and electronic components to prevent moisture, dust and other contaminants from entering. When defective chips are found in post-sequence testing, they need to be reworked. If the bottom filler has poor rework performance, it may cause damage to circuit boards and / or electronic components, reduced sealing effect and other problems. Good rework performance can reduce repair costs and shorten repair time. Summary of the invention

[0003] One of the purposes of the present application is to provide a reworkable bottom filling adhesive, which comprises, based on the total weight of 100%, 25-35% of an inorganic filler, 12-14% of a modified isosorbide-based epoxy resin, 13-16% of a bisphenol F-type epoxy resin, 13-20% of a polyether-modified epoxy resin, 12-20% of a curing agent, 8-16% of an epoxy diluent, 0.2-0.4% of an accelerator, and 0.1-0.2% of a pigment;

[0004] Among them, the structural formula of the modified isosorbide-based epoxy resin is as follows:

[0005] .

[0006] In some embodiments, the modified isosorbide-based epoxy resin is prepared by the following method:

[0007] (1) Under the condition of sodium hydroxide, epichlorohydrin and isosorbide are used as raw materials to react at a temperature of 100°C to 120°C to produce a liquid product isosorbide-based epoxy resin;

[0008] (2) Add [BMIM]Cl and 4,4-dithiodiphenylamine to isosorbide-based epoxy resin and react at 80°C to 90°C to generate modified isosorbide-based epoxy resin.

[0009] Furthermore, in step (1), the molar ratio of epichlorohydrin to isosorbide is (9-11):1; and in step (2), the mass of [BMIM]Cl is 20% of IS-EPO, and the mass ratio of MDS to IS-EPO is 1:2.

[0010] In some embodiments, the inorganic filler is selected from silica, preferably spherical silica with a particle size of 0.5-3 um.

[0011] In some embodiments, the curing agent is an amine curing agent.

[0012] In some embodiments, the epoxy diluent is a monoepoxy reactive diluent.

[0013] In some embodiments, the accelerator is an imidazole accelerator or an amine accelerator.

[0014] The second object of the present application is to provide a method for preparing the above-mentioned bottom filling glue, comprising:

[0015] Mix and stir the raw materials according to the proportion to obtain a colloid;

[0016] Use three rollers to disperse the colloid;

[0017] Then stirring and vacuum degassing are performed to obtain the bottom filling glue product.

[0018] The third purpose of the present application is to provide the use of the above-mentioned bottom filling glue in bottom filling of BGA chips or CSP chips.

[0019] Compared with the prior art, this application has the following advantages and beneficial effects:

[0020] The bottom filling glue of the present application has excellent fluidity, flexibility and reworkability; when used for bottom filling of BGA chips or CSP chips, its excellent reworkability helps to reduce maintenance costs and shorten maintenance time. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and beneficial effects of the present application more clearly understood, the present application is further described in detail below in conjunction with embodiments.

[0022] The present invention provides a reworkable bottom filling adhesive, which comprises, based on the total weight of 100%, 25-35% of an inorganic filler, 12-14% of a modified isosorbide-based epoxy resin, 13-16% of a bisphenol F-type epoxy resin, 13-20% of a polyether-modified epoxy resin, 12-20% of a curing agent, 8-16% of an epoxy diluent, 0.2-0.4% of an accelerator, and 0.1-0.2% of a pigment;

[0023] The structural formula of modified isosorbide-based epoxy resin is as follows:

[0024] .

[0025] In the present application, the curing agent is used to undergo a cross-linking reaction with the epoxy resin under the action of a certain temperature and an accelerator to generate a thermosetting compound with a three-dimensional network structure, so that the material system changes from a fluid state to a solid state; the epoxy diluent can participate in the curing reaction of the epoxy resin and become a part of the cross-linking network of the epoxy resin cured product, which can reduce the resistance encountered by the resin molecules during movement, which is manifested in the macroscopic aspect as a reduction in the viscosity of the resin matrix; the accelerator is used as a catalyst for the cross-linking reaction, promoting the cross-linking reaction and reducing the curing time.

[0026] In some embodiments, the inorganic filler is selected from silica, preferably spherical silica; the curing agent is preferably an amine curing agent, such as polyetheramine, meta-phenylenediamine, etc.; the epoxy diluent is preferably a monoepoxy reactive diluent, such as 1,4-butanediol diglycidyl ether, p-tert-butylphenyl glycidyl ether, etc.; the accelerator is selected from an imidazole accelerator or an amine accelerator, such as 2-ethyl-4-methylimidazole, 2, 4, 6-tris(dimethylaminomethyl)phenol, etc.

[0027] In some embodiments, the structure of the bisphenol F epoxy resin is as follows:

[0028] .

[0029] In some embodiments, the structure of the polyether-modified epoxy resin is as follows:

[0030] .

[0031] In some embodiments, the modified isosorbide-based epoxy resin is prepared by the following method:

[0032] Epichlorohydrin and isosorbide are added to the flask in sequence, the temperature is raised to 100°C~120°C and stirring is maintained for 3~4 hours, wherein the molar ratio of epichlorohydrin to isosorbide is (9~11):1;

[0033] Add sodium hydroxide aqueous solution and continue the reaction for 1 to 1.5 hours. Sodium hydroxide is used to neutralize chlorine. The mass fraction of sodium hydroxide aqueous solution is 1%, and the mass of sodium hydroxide is 5% to 10% of epichlorohydrin.

[0034] After suction filtration and reduced-pressure distillation, a yellow, transparent, viscous liquid product, isosorbide-based epoxy resin (IS-EPO), was obtained;

[0035] Add [BMIM]Cl to IS-EPO, stir at 80°C~90°C for 20~30 min, then add 4,4-dithiodiphenylamine (MDS), and continue stirring for 20~30 min to obtain MDS-EPO containing [BMIM]Cl; wherein the mass amount of [BMIM]Cl is 20% of IS-EPO, and the mass ratio of MDS to IS-EPO is 1:2.

[0036] In this application, modified isosorbide-based epoxy resin, bisphenol F-type epoxy resin and polyether-modified epoxy resin are compounded in specific amounts as the resin matrix of the bottom filling glue. Dynamic reversible disulfide bonds and ionic liquid [BMIM] Cl are introduced into isosorbide-based epoxy resin. Dynamic reversible disulfide bonds are weak covalent bonds that require less bonding energy. Disulfide bonds can be reorganized under a variety of conditions such as light, heat, and redox, so that thermosetting epoxy resins have excellent properties such as self-repairing and reprocessing. The addition of [BMIM] Cl converts the hydrogen bonds in the original epoxy resin network into stronger complexing in the epoxy resin-[BMIM] Cl network, which plays a role in toughening the epoxy resin. By combining the modified isosorbide-based epoxy resin with a specific epoxy resin and a specific curing agent, a bottom filling glue with excellent fluidity, flexibility and reworkability can be obtained.

[0037] The present application provides a method for preparing the above-mentioned bottom filling glue, comprising:

[0038] (1) Mix and stir the raw materials according to the proportions to obtain a colloid;

[0039] In some embodiments, this step is specifically as follows: adding the raw materials according to the proportion into a mixing cup, and stirring with a centrifugal mixer; the rotation speed and orbital speed of the centrifugal mixer are 1000-1100 r / min and 1300-1400 r / min respectively, and the stirring time is 95-115 s;

[0040] (2) Using three rollers to disperse the colloid to obtain a uniformly dispersed bottom filling glue;

[0041] In some embodiments, the feeding gap of the three rollers is 20um~35um, and the discharging gap is 5um~15um;

[0042] (3) The evenly dispersed bottom filling adhesive is vacuum degassed to obtain a bottom filling adhesive product.

[0043] In some embodiments, vacuum degassing is performed using a centrifugal mixer, the rotation speed and orbital speed of the centrifugal mixer are 1000-1100 r / min and 1300-1400 r / min respectively, and the vacuum degassing time is 65-95 s.

[0044] The raw materials used in the embodiments and comparative examples are as follows:

[0045] Inorganic filler: spherical silica with a particle size of 0.5~3um purchased from the market;

[0046] Bisphenol F epoxy resin: KF-8110 bisphenol F epoxy resin, YLSE-162L bisphenol F epoxy resin;

[0047] Polyether modified epoxy resin: JRE-260 polyether modified epoxy resin, JRE-320 polyether modified epoxy resin;

[0048] Epoxy diluent: JRD-130, whose component is 1,4-butanediol diglycidyl ether; JRD-509, whose component is p-tert-butylphenyl glycidyl ether;

[0049] Curing agent: D230, its ingredients are polyetheramine; meta-xylylenediamine curing agent;

[0050] Pigment: commercially available carbon black;

[0051] Accelerator: 2, 4, 6-tris(dimethylaminomethyl)phenol (DMP-30), 2-ethyl-4-methylimidazole.

[0052] The following table lists the viscosity and epoxy equivalent of the above bisphenol F type epoxy resin and polyether modified epoxy resin.

[0053] Table 1 Viscosity and epoxy equivalent weight of bisphenol F epoxy resin and polyether modified epoxy resin

[0054]

[0055] The modified isosorbide-based epoxy resin in the examples and comparative examples is homemade, and its preparation method is as follows:

[0056] Epichlorohydrin and isosorbide were added to the flask in sequence, the temperature was raised to 110°C and stirring was maintained for 3.5 hours, wherein the molar ratio of epichlorohydrin to isosorbide was 10:1;

[0057] A sodium hydroxide aqueous solution with a mass concentration of 1% was added, and the reaction was continued for 1 hour. The sodium hydroxide was used to neutralize the chlorine. The amount of the sodium hydroxide aqueous solution was calculated based on the amount of sodium hydroxide. In this embodiment, the mass amount of sodium hydroxide was 8% of epichlorohydrin.

[0058] After suction filtration and reduced-pressure distillation, a yellow, transparent, viscous liquid product, isosorbide-based epoxy resin (IS-EPO), was obtained;

[0059] [BMIM]Cl was added to IS-EPO, stirred at 85°C for 25 min, and then 4,4-dithiodiphenylamine (MDS) was added, and stirring was continued for 20 min to obtain MDS-EPO containing [BMIM]Cl; wherein the mass amount of [BMIM]Cl was 20% of IS-EPO, and the mass ratio of MDS to IS-EPO was 1:2.

[0060] [BMIM]Cl selected 1-butyl-3-methylimidazolium chloride.

[0061] The embodiments and comparative examples provided in this application are as follows:

[0062] Example 1

[0063] The raw materials and the amounts of the raw materials in this embodiment are as follows:

[0064] Inorganic filler: 25%;

[0065] Modified isosorbide-based epoxy resin: 14%;

[0066] Bisphenol F epoxy resin: 14%;

[0067] Polyether modified epoxy resin: 14%;

[0068] Curing agent: 20%;

[0069] Epoxy diluent 12.5%;

[0070] Accelerator 0.35%;

[0071] Pigment: 0.15%.

[0072] In this embodiment, the bisphenol F epoxy resin is YLSE-162L bisphenol F epoxy resin, the polyether modified epoxy resin is JRE-260 polyether modified epoxy resin, the curing agent is D230, the epoxy diluent is JRD-130, and the accelerator is 2-ethyl-4-methylimidazole.

[0073] Example 2

[0074] The raw materials and the amounts of the raw materials in this embodiment are as follows:

[0075] Inorganic fillers: 27%;

[0076] Modified isosorbide-based epoxy resin: 13%;

[0077] Bisphenol F epoxy resin: 13%;

[0078] Polyether modified epoxy resin: 13%;

[0079] Curing agent: 18%;

[0080] Epoxy diluent 15.5%;

[0081] Accelerator 0.35%;

[0082] Pigment: 0.15%.

[0083] In this embodiment, the bisphenol F epoxy resin is KF-8110 bisphenol F epoxy resin, the polyether modified epoxy resin is JRE-320 polyether modified epoxy resin, the curing agent is m-xylylenediamine curing agent, the epoxy diluent is JRD-509, and the accelerator is DMP-30.

[0084] Example 3

[0085] The raw materials and the amounts of the raw materials in this embodiment are as follows:

[0086] Inorganic filler: 30%;

[0087] Modified isosorbide-based epoxy resin: 12%;

[0088] Bisphenol F epoxy resin: 14%;

[0089] Polyether modified epoxy resin: 12%;

[0090] Curing agent: 15.5%;

[0091] Epoxy diluent 16%;

[0092] Accelerator 0.35%;

[0093] Pigment: 0.15%.

[0094] In this embodiment, the bisphenol F epoxy resin is YLSE-162L bisphenol F epoxy resin, the polyether modified epoxy resin is JRE-260 polyether modified epoxy resin, the curing agent is D230, the epoxy diluent is JRD-130, and the accelerator is 2-ethyl-4-methylimidazole.

[0095] Example 4

[0096] The raw materials and the amounts of the raw materials in this embodiment are as follows:

[0097] Inorganic filler: 35%;

[0098] Modified isosorbide-based epoxy resin: 14%;

[0099] Bisphenol F epoxy resin: 16%;

[0100] Polyether modified epoxy resin: 14%;

[0101] Curing agent: 12%;

[0102] Epoxy diluent 8.5%;

[0103] Accelerator 0.35%;

[0104] Pigment: 0.15%.

[0105] In this embodiment, the bisphenol F epoxy resin is KF-8110 bisphenol F epoxy resin, the polyether modified epoxy resin is JRE-320 polyether modified epoxy resin, the curing agent is m-xylylenediamine curing agent, the epoxy diluent is JRD-509, and the accelerator is DMP-30.

[0106] Comparative Example 1

[0107] The raw materials and the amounts of each raw material used in this comparative example are as follows:

[0108] Inorganic filler: 30%;

[0109] Bisphenol F epoxy resin: 21%;

[0110] Polyether modified epoxy resin: 21%;

[0111] Curing agent: 18%;

[0112] Epoxy diluent 9.5%;

[0113] Accelerator 0.35%;

[0114] Pigment: 0.15%.

[0115] In this embodiment, the bisphenol F epoxy resin is KF-8110 bisphenol F epoxy resin, the polyether modified epoxy resin is JRE-260 polyether modified epoxy resin, the curing agent is D230, the epoxy diluent is JRD-130, and the accelerator is DMP-30.

[0116] Comparative Example 2

[0117] The raw materials and the amounts of each raw material used in this comparative example are as follows:

[0118] Inorganic fillers: 36%;

[0119] Modified isosorbide-based epoxy resin: 15%;

[0120] Bisphenol F epoxy resin: 15%;

[0121] Polyether modified epoxy resin: 15%;

[0122] Curing agent: 11%;

[0123] Epoxy diluent 7.5%;

[0124] Accelerator 0.35%;

[0125] Pigment: 0.15%.

[0126] In this embodiment, the bisphenol F epoxy resin is selected from YLSE-162L bisphenol F epoxy resin, the polyether modified epoxy resin is selected from JRE-320 polyether modified epoxy resin, the curing agent is selected from m-xylylenediamine curing agent, the epoxy diluent is selected from JRD-509, and the accelerator is selected from 2-ethyl-4-methylimidazole.

[0127] Comparative Example 3

[0128] The raw materials and the amounts of each raw material used in this comparative example are as follows:

[0129] Inorganic fillers: 24%;

[0130] Modified isosorbide-based epoxy resin: 13%;

[0131] Bisphenol F epoxy resin: 13%;

[0132] Polyether modified epoxy resin: 11%;

[0133] Curing agent: 21%;

[0134] Epoxy diluent 17.5%;

[0135] Accelerator 0.35%;

[0136] Pigment: 0.15%.

[0137] In this embodiment, the bisphenol F epoxy resin is KF-8110 bisphenol F epoxy resin, the polyether modified epoxy resin is JRE-320 polyether modified epoxy resin, the curing agent is m-xylylenediamine curing agent, the epoxy diluent is JRD-509, and the accelerator is DMP-30.

[0138] In the above embodiments and comparative examples, the inorganic filler is spherical silica with a particle size of 0.5-3 μm, and the pigment is carbon black.

[0139] The preparation processes of the above-mentioned examples and comparative examples are the same, which are as follows:

[0140] (1) Add all raw materials according to the proportion into a mixing cup and stir them with a centrifugal mixer; the rotation speed and orbital speed of the centrifugal mixer are 1050 r / min and 1350 r / min respectively, and the stirring time is 100 s;

[0141] (2) Using three rollers to disperse the colloid to obtain a uniformly dispersed bottom filling glue; wherein the feeding gap of the three rollers is 25 um and the discharging gap is 10 um;

[0142] (3) The evenly dispersed bottom filling glue is vacuum degassed using a centrifugal mixer. The rotational speed and orbital speed of the centrifugal mixer are 1050 r / min and 1350 r / min, respectively, and the vacuum degassed time is 90 s.

[0143] The performance parameter detection methods of the products of the embodiments and comparative examples are as follows:

[0144] 1. Viscosity:

[0145] The viscosity was tested at 25°C using a digital rotational viscometer, with a 14# rotor and a rotation speed of 200 r / min.

[0146] 2. Liquidity:

[0147] Place a 25mm long and 15mm wide silicon wafer with copper pillars on the PCB and fix it. Place the PCB on a 110℃ hot plate and preheat it for one minute. Use a dispensing machine to dispense 40mg~45mg of the bottom filling glue to be tested along the long side of the silicon wafer. Under the action of capillary force, the bottom filling glue will flow to the bottom of the silicon wafer, and record the time it takes to fill the entire silicon wafer.

[0148] 3. Glass transition temperature Tg and elastic modulus:

[0149] The glass transition temperature and elastic modulus were tested by a dynamic thermomechanical analyzer. The reference standard was ASTM E2254-2018. A fully cured test sample was taken with a size of 55 mm × 10 mm × 3 mm. Test parameters were dual cantilever mode, vibration frequency of 1 Hz, amplitude of 10 μm, heating rate of 5 °C / min, and test temperature of 150 °C.

[0150] 4. Elongation:

[0151] Use an electronic universal material testing machine to take a completely cured test sample with dimensions of 30mm×5mm×(0.2~0.5)mm and a test speed of 0.1 mm / min.

[0152] 5.Reworkability:

[0153] Take a circuit substrate with a BGA chip. The size of the BGA chip is 10mm×10mm (0.5mm pitch, 121 pins, 0.35mm diameter solder ball). First, fill the gap between the BGA chip and the circuit substrate with bottom filler. Then heat it at 200℃. After the joints of the solder bumps are dissolved, peel off the BGA chip with tweezers. Finally, confirm the workability of the return substrate after removing the filler from the return substrate.

[0154] The evaluation criteria for reworkability are defined as follows:

[0155] Good reworkability: BGA and bottom filler can be easily removed from the circuit substrate without peeling of the resin on the circuit substrate surface;

[0156] Poor reworkability: BGA and bottom filler can be easily removed from the circuit substrate, but the resin on the circuit substrate surface may peel off;

[0157] Reworkability is very poor: BGA and underfill are difficult to remove, and surface resin peels off.

[0158] The test data of the products of the above embodiments and comparative examples are shown in Table 2 below:

[0159] Table 2 Performance parameter data of the products of the embodiments and comparative examples

[0160]

[0161] From the performance parameter data in Table 2, it can be seen that the products of Examples 1 to 4 have excellent fluidity, flexibility and reworkability, and the elastic modulus at 150°C is less than 60MPa, and can be reworked at a temperature higher than 150°C. The softened adhesive layer can be easily physically removed, and the rework temperature is not higher than the melting point of lead-free solder, so the reworkability is good and easy to rework. Comparative Example 1 does not add homemade epoxy resin, and the product has poor flexibility and reworkability; although Comparative Examples 2 to 3 add homemade epoxy resin, the amount used is different, and the comprehensive performance of fluidity, flexibility and reworkability is poor.

[0162] The inventors analyzed the mechanism by which the present application achieves the above technical effects as follows:

[0163] Epoxy resin has problems such as high brittleness, easy cracking, and poor elastic modulus, which affect its scope of use and reduce its service life. In order to solve the above problems and maintain the integrity of the epoxy resin network, this paper introduces dynamic reversible disulfide bonds and [BMIM] Cl into the epoxy resin network. Dynamic reversible disulfide bonds are relatively weak covalent bonds, and the required bonding energy is relatively small. Therefore, disulfide bonds can be reorganized under various conditions such as light, heat, and redox, so that thermosetting epoxy resins have excellent properties such as self-repair and reprocessing molding; the addition of [BMIM] Cl transforms the hydrogen bonds in the original epoxy resin network into stronger complexing in the epoxy resin-[BMIM] Cl network, which plays a role in toughening the epoxy resin. This modified resin and other types of epoxy resins are used in combination with suitable curing agents to prepare bottom filling adhesives with appropriate viscosity, bonding strength, flexibility and good rework performance.

[0164] The above embodiments are only for the purpose of clearly illustrating the embodiments, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above descriptions. It is not necessary and impossible to list all the implementation methods here, so the obvious changes or modifications derived are still within the protection scope of the invention.

Claims

1. A reworkable bottom filler, characterized in that: Taking the total weight as 100%, it includes: 25-35% inorganic filler, 12-14% modified isosorbide-based epoxy resin, 13-16% bisphenol F epoxy resin, 13-20% polyether modified epoxy resin, 12-20% curing agent, 8-16% epoxy diluent, 0.2-0.4% accelerator, and 0.1-0.2% pigment; Among them, the structural formula of the modified isosorbide-based epoxy resin is as follows: ； The inorganic filler is spherical silica with a particle size of 0.5-3 um; The curing agent is an amine curing agent; The epoxy diluent is a monoepoxy reactive diluent; The accelerator is an imidazole accelerator or an amine accelerator.

2. The reworkable bottom filler according to claim 1, wherein: The modified isosorbide-based epoxy resin is prepared by the following method: Step (1), using epichlorohydrin and isosorbide as raw materials, reacting at a temperature of 100° C. to 120° C. in the presence of sodium hydroxide to produce a liquid product, isosorbide-based epoxy resin; Step (2), adding 1-butyl-3-methylimidazolium chloride [BMIM] Cl and 4,4-dithiodiphenylamine MDS to the isosorbide-based epoxy resin, and reacting at a temperature of 80° C. to 90° C. to generate a modified isosorbide-based epoxy resin IS-EPO.

3. The reworkable bottom filler according to claim 2, wherein: In step (1), the molar ratio of epichlorohydrin to isosorbide is (9-11):1; and in step (2), the mass of [BMIM]Cl is 20% of IS-EPO, and the mass ratio of MDS to IS-EPO is 1:

2.

4. The method for preparing the bottom filling glue according to any one of claims 1 to 3, characterized in that: include: Mix and stir the raw materials according to the proportion to obtain a colloid; Use three rollers to disperse the colloid; Then stirring and vacuum degassing are performed to obtain the bottom filling glue product.

5. Use of the bottom filling adhesive according to any one of claims 1 to 3 for bottom filling of a BGA chip or a CSP chip.

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