JP6196132B2 - Metal foil for press bonding and electronic component package - Google Patents

Description

  The present invention relates to a metal foil for press bonding provided with a conductive resin layer, and an electronic component package using the same.

  As a method of mounting a semiconductor chip and a printed wiring board, a conductive film is sandwiched between the electrodes (pads) of the semiconductor chip and the board wiring electrodes, and thermocompression bonding is performed. A flip chip mounting technique is known in which electrical conduction is made by conductive particles in a conductive film.

  In addition, an electromagnetic shielding film as a conductive film is attached to a printed wiring board, or an electromagnetic shielding film is mounted between a transmission system circuit and a reception system circuit mounted on a printed circuit board to couple the two. It is also done to prevent.

  As this type of conductive film, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2003-298285), as an electromagnetic wave shielding adhesive film, a conductive adhesive layer and, if necessary, a metal thin film on one side of a cover film There is disclosed a reinforced shield film having a shield layer composed of layers, in which an adhesive layer and a releasable reinforcing film are sequentially laminated on the other surface.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-273577) discloses a shield film having a shield layer and a base film made of an aromatic polyamide resin, and a method for forming a resonance circuit using the shield film, Several through holes are opened in the cover lay of the flexible printed wiring board and processed so that the ground circuit (earth circuit) is exposed, and then the conductive adhesive layer of the shield film and the cover lay are attached by hot press. A method of forming a resonance circuit between the ground of the circuit and the silver deposition layer by forming a joint portion between the ground circuit and the conductive adhesive layer after being combined is disclosed.

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2007-189091) discloses an isotropic conductive adhesive sheet including a release film and an isotropic conductive adhesive layer containing conductive particles and a binder. As the usage method, after temporarily fixing the adhesive sheet with the release film to the circuit board, the release film is peeled off, the reinforcing plate is superimposed on the surface of the conductive adhesive layer, and press working (130 to 190 ° C., 1 to 4 MPa), and a method of electrically connecting the reinforcing plate and the electrode via the low melting point metal powder is disclosed.

  Patent Document 4 (Japanese Patent Application Laid-Open No. 2009-191099) includes a conductive adhesive layer formed in a film shape having a large number of conductive particles and a binder in which these conductive particles are dispersed, and has tackiness. A conductive adhesive sheet having a tacky resin layer is disclosed.

  Patent Document 5 (Japanese Unexamined Patent Application Publication No. 2010-168518) discloses an adhesive material made of a thermoplastic elastomer resin, an acrylic resin, or the like formed in a sheet shape, Ag coated Cu powder dispersed in the adhesive material, It has a conductive adhesive layer composed of a composition having conductive particles such as Ag-coated Ni powder, and the average value of the thickness of the adhesive substance with respect to the average particle diameter of the conductive particles is There is disclosed a conductive pressure-sensitive adhesive sheet that is in a range of 0.8 times to 1.4 times and in which the content of the conductive particles is in a range of 15 to 25% by mass of the entire conductive adhesive layer.

  In Patent Document 6 (Japanese Patent Laid-Open No. 2011-66329), heating and pressurization are performed on a conductive member provided with a metal layer for connection to an external ground member and a conductive adhesive layer containing conductive particles in contact. A shield film connected by the above, formed from the resin softened by the heating, and after being connected by the heating and pressurization, the average protruding length of the conductive particles protruding from the conductive adhesive layer A shield film comprising: a cover film formed with a thin layer thickness; and a cover film adhered to the conductive adhesive layer; and a metal thin film layer and an adhesive layer sequentially laminated on the cover film. As a ground connection method using this, a metal layer connected to an external ground member and a conductive adhesive layer containing conductive particles are connected. The conductive member provided in a state is pressurized while being heated at a temperature at which the resin is softened to bond the conductive adhesive layer and the cover film, thereby projecting the conductive material longer than the layer thickness of the cover film. A ground connection method for a shield film is disclosed, in which the conductive particles reach the metal thin film layer to be grounded.

  Patent Document 7 (Japanese Patent Laid-Open No. 2011-166100) discloses an electromagnetic wave shielding adhesive film comprising a curable insulating layer, a conductive film, and a curable conductive adhesive layer in this order, The conductive coating is a coating formed from a dispersion containing coated conductive particles having an average particle diameter of 0.001 to 0.5 μm formed by coating conductive particles with a protective substance, and the curable conductive adhesive An electromagnetic wave shielding adhesive film is disclosed, wherein the agent layer contains a curable insulating resin and a metal powder having an average particle diameter of 1 to 50 μm. The curable conductive adhesive layer is superimposed on an adherend such as a printed wiring board and heated to cure the curable conductive adhesive layer and the curable insulating layer. It becomes possible to shield the adherend from electromagnetic waves.

  Patent Document 8 (Japanese Patent Application Laid-Open No. 2011-187895) discloses an electromagnetic wave shielding film in which a protective layer is laminated on a conductive layer made of (A) metal powder and (B) a binder resin. ) Conductivity containing flaky metal powder having an average thickness of 50 to 300 nm and an average particle diameter of 3 to 10 μm, and (b) acicular or dendritic metal powder (particularly silver-coated copper powder) having an average particle diameter of 3 to 10 μm. What is formed from an adhesive paste is disclosed.

  Patent Document 9 (Japanese Patent Application Laid-Open No. 2011-171523) discloses an electromagnetic wave shielding adhesive film comprising an insulating film having no curability, a conductive coating, and a curable conductive adhesive layer in this order. The conductive film is a film formed from a dispersion containing coated conductive particles having an average particle diameter of 0.001 to 0.5 μm, in which conductive particles are coated with a protective substance, and the curability is An electromagnetic wave shielding adhesive film is disclosed, wherein the conductive adhesive layer contains a curable insulating resin and a metal powder having an average particle diameter of 1 to 50 μm.

JP 2003-298285 A JP 2004-273577 A JP 2007-189091 A JP 2009-191099 A JP 2010-168518 A JP 2011-66329 A JP 2011-166100 A JP 2011-187895 A JP 2011-171523 A

  In the manufacturing method of the electronic component package, after mounting the electronic component on the circuit board and sealing the electronic component with a mold resin, the mold resin between the electronic components is removed by half-cut dicing to provide a groove portion, and the mold The conductive paste is applied on the resin to fill the groove with the conductive paste, and then diced along the center of the groove to divide the package into electronic packages. The way is done.

In producing such an electronic component package, the step of applying a conductive paste is a step of heat-pressing a metal foil on which a resin layer containing conductive particles is laminated, for example, the resin layer is stacked on a circuit board. If heating and pressing from the metal foil side can replace the resin and conductive particles in the resin layer with the step of filling the groove portion provided in the circuit board, the manufacturing process of the electronic component package is simplified. Can be
However, since the grooves and holes provided in the circuit board tend to become finer, the resin or conductive particles are filled to every corner of the narrow grooves or small holes by hot pressing the metal foil as described above. In addition, it was a problem whether it was possible to establish electrical conduction reliably.

  Therefore, the present invention relates to a metal foil for press bonding used for heat pressing as described above, and can be filled with resin or conductive particles to every corner of a narrow groove or small hole, and reliably conductive. It is intended to provide a new metal foil for press bonding that can take the following steps.

  The present invention is a press-bonding metal foil comprising a metal foil and a resin layer (also referred to as “conductive resin layer”) A containing conductive particles in a B-stage resin. Among the conductive particles in A, the circularity degree of the conductive particles (referred to as “cumulative 50%”) in the cumulative number of 50 counts counted from the higher circularity is 0.80 or more, and the resin layer Among the conductive particles in A, the circularity (referred to as “cumulative 90%”) of the conductive particles in the frequency cumulative 90 number% counted from the higher circularity is 0.60 or more, and the resin layer Proposed is a metal foil for press bonding, wherein the standard deviation of the circularity of the conductive particles in A is 0.140 or less, and the content of the conductive particles in the resin layer A is 75 wt% or more. .

  The metal foil for press bonding proposed by the present invention is, for example, a resin layer of the metal foil for press bonding provided on a printed wiring board having a configuration in which an electronic component is mounted and the electronic component is sealed with a mold resin. A is overlapped, the resin of the resin layer A is heated and softened or melted, the metal foil for press bonding is pressed to the substrate side, and further heated to cure the softened or melted resin. Thus, the resin and conductive particles of the resin layer A can be filled in the grooves or holes provided in the circuit board, and an electronic component package can be manufactured.

  Regarding the metal foil for press bonding proposed by the present invention, by adjusting the shape of the conductive particles to a predetermined range and defining the content thereof, that is, the circularity (cumulative) of the conductive particles in the resin layer A. 50%) is 0.80 or more, the circularity of the conductive particles in the resin layer A (cumulative 90%) is 0.60 or more, and the circularity of the conductive particles in the resin layer A In addition to defining the shape of the conductive particles so that the standard deviation is 0.140 or less, the content of the conductive particles is set so that the content of the conductive particles in the resin layer A is 75 wt% or more. By prescribing, the resin or conductive particles of the resin layer A can be filled to every corner of a narrow groove or small hole, and conduction can be ensured and the cost can be reduced. It became possible to plan.

BRIEF DESCRIPTION OF THE DRAWINGS It is an example of the usage method of this press-bonding metal foil which concerns on an example of this invention, (A) is the state (before press bonding) which accumulated this press-bonding metal foil on the to-be-adhered body, (B) is deposition It is the figure which showed the state after press-bonding this press-bonding metal foil to a body. It is a model figure for demonstrating the shape of electroconductive particle, (A) is dendrite-like, (B) is acicular, (C) is bowl-like, (D) is a projection spherical, (E) is a projection It shows a saddle shape.

  Hereinafter, embodiments of the present invention will be described in detail. However, the scope of the present invention is not limited to the following embodiments.

<Metal foil for press bonding>
A metal foil for press bonding according to an example of the present embodiment (referred to as “metal foil for press bonding”) includes a metal foil and a resin layer A containing granular conductive particles in a B-stage resin. And a metal foil for press bonding. As will be described in detail later, the metal foil for press bonding is placed in a groove or hole provided in the circuit board by superposing the resin layer A of the metal foil for press bonding on the circuit board and heating and pressing. The resin of the resin layer A and conductive particles can be filled, and the metal foil for press bonding can be bonded to a circuit board (in the present invention, such filling and bonding means is referred to as “press bonding”). ).

  This press-bonding metal foil may include one or more layers other than the metal foil and the resin layer A. For example, a release sheet may be laminated on the surface of the resin A opposite to the metal foil.

(Metal foil)
The metal foil in this press-bonding metal foil may be a metal foil that can function as, for example, a conductive layer or an electrode layer in an electronic circuit or an electronic component.
Such a metal foil is preferably a metal foil obtained by a rolling method or an electrolytic method. For example, copper foil, nickel foil, copper alloy foil (brass foil, corson alloy foil etc.), nickel alloy foil (nickel-phosphorus alloy foil, nickel-cobalt alloy foil etc.) etc. can be mentioned. However, it is not limited to these.

  If the thickness of the metal foil is too thin, it is difficult to form the resin layer A. On the other hand, if the thickness is too thick, the cost is high. Therefore, the thickness is preferably 1 μm to 50 μm, more preferably 2 μm or more or 30 μm or less, especially 3 μm. The thickness is preferably 20 μm or less.

In consideration of forming an electronic circuit by etching or the like, it is preferable to use a metal foil having a single composition from the viewpoint of satisfactorily forming a fine conductive pattern or a fine electrode pattern.
In consideration of the fact that the metal foil is used as the conductive layer, the metal foil has a lower electrical resistivity than nickel and is a metal foil made of copper or a copper alloy which is a non-magnetic material. preferable. Copper foil is preferable in that it is easy to process such as etching and is inexpensive.

(Resin layer A)
The resin composition which comprises the resin layer A should just be a resin composition which can be in a B stage state. Usually, this type of base resin is generally a thermosetting resin. However, a mixture of a thermoplastic resin and a thermosetting resin can also be used.

  Here, the B stage state means an intermediate curing state of a thermosetting resin having adhesiveness or tackiness. Among them, it is preferable that the film or sheet can be maintained, and the resin is once softened or melted when heated and cured when heated.

  As a method for bringing the resin composition into a B-stage state, 1) a method for volatilizing a solvent as appropriate, 2) a method for forcibly stopping a curing reaction in the middle, and 3) two or more types of curable resins having different curing regions. 4) Other known methods can be employed.

The resin that forms the main component of the resin composition that can be in the B-stage state (referred to as “base resin”) is not particularly limited. For example, epoxy resin, polydimethylsiloxane resin, acrylic resin, other organic functional polysiloxane resin, polyimide resin, fluorocarbon resin, benzocyclobutene resin, fluorinated polyallyl ether, polyamide resin, polyimide amide resin, phenol cresol resin , Aromatic polyester resins, polyphenylene ether resins, bismaleimide triazine resins, fluororesins, and the like. Among these, one or a mixture of two or more of them may be used. The base resin is a resin having the largest content among the resin components constituting the resin composition.
Also, as curable or crosslinkable materials, epoxy resins, acrylic resins, polydimethylsiloxane resins that can be crosslinked by free radical polymerization, atom transfer, radical polymerization, ring opening polymerization, ring opening metathesis polymerization, anionic polymerization, or cationic polymerization. Or one or more of other organofunctional polysiloxane resins may be blended.

  Among them, the resin composition constituting the resin layer A is preferably a resin composition having a minimum melt viscosity of 10 Pa · s to 1000000 Pa · s at 100 to 150 ° C., and more preferably a resin composition of 100 Pa · s or more. Is even more preferable.

As an example of the resin composition constituting the resin layer A, a resin composition containing an epoxy resin as a base resin, an epoxy curing agent, an organic solvent, a silane coupling agent, a surfactant, and the like can be given. If it is such a resin composition, this resin composition can be made into a B-stage state by volatilizing an organic solvent. In this case, for example, the same applies even when a polymer blend of an acrylic resin and an epoxy resin is used as the base resin.
However, these are only examples.

  Examples of the material added for thermosetting include thermosetting agents such as organic peroxides, isocyanate compounds, epoxy compounds, and amine compounds.

(Conductive particles)
As the conductive particles contained in the resin layer A, for example, conductive particles such as silver powder particles, copper powder particles, and iron powder particles, or particles made of an arbitrary material, for example, the conductive particles as a core material of these surfaces. The particle | grains etc. which coat | cover one part or all part with different electroconductive materials, for example, gold | metal | money, silver, copper, nickel, tin, etc. can be mentioned. However, the present invention is not limited to these, and any material having conductivity can be arbitrarily adopted.

Regarding the shape of the conductive particles, the circularity of the conductive particles in a cumulative number of 50% by number counted from the higher circularity of the conductive particles in the resin layer A from the viewpoint of being available relatively inexpensively ( (Referred to as “cumulative 50%”) is 0.80 or more, particularly 0.85 or more, or 1.00 or less, and more preferably 0.90 or more.
Further, among the conductive particles in the resin layer A, the circularity of the conductive particles (referred to as “cumulative 90%”) in the cumulative number of 90% counted from the higher circularity is 0.60 or more, especially 0 .65 or more or 0.95 or less, more preferably 0.75 or more.
In addition, the above “cumulative 50%” or “cumulative 90%” indicates that the number of conductive particles in the resin layer A from the highest circularity (circularity = 1.0) to the lower one. , And the circularity when the cumulative number reaches 50% or 90% is shown.
Furthermore, the standard deviation of the circularity of the conductive particles in the resin layer A is 0.140 or less, more preferably 0.010 or more, or 0.120 or less, and more preferably 0.110 or less.

  In order to adjust the circularity of the conductive particles to the above range, for example, the shape of the conductive particles and the content ratio thereof may be adjusted. For example, spherical and substantially spherical particles have a relatively high degree of circularity, while dendritic, needle-like, flake, and bowl-like particles have a relatively low degree of circularity. Increasing the circularity of the conductive particles can increase the circularity of the conductive particles. On the other hand, increasing the content ratio of dendritic, needle-like, flake-like, and bowl-like particles can reduce the circularity of the conductive particles. (See FIG. 2). However, it is not limited to such a method.

  If the particle size of the conductive particles contained in the resin layer A is too large, the particles may settle in the paste (paint), cannot be thinned, or the electromagnetic shielding characteristics may be deteriorated, but are too small. And dispersibility may fall, paste (paint) may thicken, and coating property may fall. For this reason, the average equivalent circle diameter of the conductive particles contained in the resin layer A is preferably 0.1 μm to 30 μm, more preferably 0.3 μm or more and 20 μm or less, and particularly preferably 0.5 μm or more or 10 μm or less. Even more preferred.

  The content of the conductive particles in the resin layer A is such that the content of the conductive particles in the resin layer A is 75 wt% or more, of which 80 wt% or more among them, It is more preferable that it is 98 wt% or less, and it is still more preferable that it is 85 wt% or more or 95 wt% or less among them.

The resin layer A has a resin flow (refer to the example of measurement method) of 3 to 20% from the viewpoint of, for example, ensuring filling into grooves and holes provided on the circuit board. Among them, it is preferably 5% or more and 17% or less, more preferably 7% or more and 15% or less.
In order to adjust the resin flow of the resin layer A, the type of resin constituting the resin layer A and the shape and content of the conductive particles may be adjusted.

  The thickness of the resin layer A is not particularly limited. However, even if it is too thick, the effect is not increased and the material is wasted. On the other hand, if it is too thin, it becomes difficult to follow the unevenness of the adherend surface, and it is difficult to ensure stable conductivity with the resin layer A. Become. Therefore, the thickness of the resin layer A is preferably 1 μm to 500 μm, more preferably 300 μm or less, and particularly preferably 200 μm or less. However, since the thickness depends on the volume of the groove when embedded in the groove, the thickness of the resin layer A is preferably set in a desired range with an upper limit of 500 μm depending on the groove volume.

(Metal foil surface layer)
As needed, you may provide the structure by which the metal foil surface on the opposite side to the resin layer A is antioxidant processed. However, it is not absolutely necessary.
Since metal foil, especially copper foil, is easily oxidized, it is preferable to subject the surface of the metal foil to an antioxidant treatment.

  Antioxidation treatment includes chemical treatment to form a triiron tetroxide film (black), chemical treatment to form a phosphoric acid (zinc phosphate and manganese phosphate) film on the surface, chromate treatment, electroless nickel plating, An alumite treatment etc. can be mentioned. However, it is not limited to these processes.

<Method for producing metal foil for press bonding>
Conductive particles, and, if necessary, a curing agent, a coupling agent, a corrosion inhibitor, and the like are added to the resin composition that can be in a B-stage state and mixed to disperse the conductive particles without breaking the shape. Thus, it is preferable to form a resin layer A by kneading into a paste (coating material), applying the paste (coating material) onto a metal foil, and evaporating the solvent to make the resin composition B-staged. .
During kneading, avoid the use of a stirrer that gives mechanical impact to the conductive particles so that the particle shape of the conductive particles does not collapse. It is preferable to use kneading without mechanical impact.

<How to use this press-bonding metal foil>
As shown in FIG. 1A, the metal foil for press bonding is formed by stacking the resin layer A of the metal foil for press bonding on a circuit board provided with fine grooves and holes by mold resin or the like. A hot plate or the like is brought into contact with the surface of the metal foil, the resin layer A is heated through the metal foil to soften or melt the resin of the resin layer A, and the surface of the metal foil is pressed with the press hot plate or the like. In other words, by pressing (pressing) the surface of the metal foil in the direction of the adherend with the surface to be pressed as the pressed surface, the resin and conductive particles of the resin layer A are filled in the grooves and holes provided in the circuit board. can do.
Then, the metal foil for press bonding can be bonded to the adherend by further heating and curing the resin softened or melted as described above.
As shown in FIG. 1 (B), the press-bonding metal foil is hot-pressed in this manner, so that the resin and conductive particles of the resin layer A are placed in the grooves and holes provided in the circuit board. Can be filled, and conduction can be ensured.

  For example, in a printed wiring board having a configuration in which an electronic component is mounted, the electronic component is sealed with a mold resin, and a cut groove is provided by half dicing, the resin layer A of the metal foil for press bonding is The resin layer A is heated and softened or melted through the metal foil by, for example, pressing a hot plate or the like against the metal foil, and then the surface of the metal foil is The conductive film for press bonding is pressed to the substrate side as a pressed surface, and then further heated to cure the softened or melted resin so that the resin of the resin layer A covers the mold resin portion. At the same time, the resin and conductive particles of the resin layer A enter and fill the cut grooves. In this way, an electronic component package can be manufactured.

<Explanation of words>
In the present specification, when expressed as “X to Y” (X and Y are arbitrary numbers), “X is preferably greater than X” or “preferably more than Y” with the meaning of “X to Y” unless otherwise specified. The meaning of “small” is also included.
In addition, when expressed as “X or more” (X is an arbitrary number), it means “preferably larger than X” unless otherwise specified, and expressed as “Y or less” (Y is an arbitrary number). In the case, unless otherwise specified, the meaning of “preferably smaller than Y” is included.

  Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

<Metal foil>
As the metal foil, a high-tensile copper foil having a thickness of 9 μm (product name “HTE”, manufactured by Mitsui Metal Mining Co., Ltd.) was used.

<Conductive powder>
(1) Conductive powder A: Silver-coated copper powder composed of spherical particles.
(2) Conductive powder B: Silver-coated copper powder composed of particles having a flake shape.
(3) Conductive powder C: Silver-coated copper powder composed of particles having a flake shape.
(4) Conductive powder D: Silver-coated copper powder composed of spherical particles.
(5) Conductive powder E: Silver-coated copper powder comprising dendritic particles.
(6) Conductive powder F: Silver-coated copper powder composed of potato-like particles.
The silver-coated copper powder means a powder composed of particles obtained by coating the surface of copper powder particles with silver.

<Resin>
Epoxy resin X: An epoxy resin composition having a melt viscosity of 2000 cp at 100 ° C. was used.
The melt viscosity of the resin is 5 mm, and a viscosity measuring device (“HAAKE Rheo Stress 600” manufactured by Thermo ELECTRON CORPORATION) is used. The temperature (temperature rate) is 2 ° C./min. Measurements were made with appropriate adjustments.

<Example 1-6 and Comparative Example 1-4>
Add the amount (conducting particle content) and the kind of conductive powder shown in Table 1 to the epoxy resin X, and knead for 3 minutes at a rotational speed of 2000 rpm using a stirrer (Awatori Kentaro (trade name)). After preparing the paste, on the copper foil having a thickness of 9 μm and the film made of polyethylene terephthalate having a thickness of 35 μm (referred to as “PET film”), the applicator is used so that the dry thickness becomes 100 μm. A paste is applied to form a coating film, heated in an oven at 150 ° C. for 3 minutes, a copper foil for press bonding provided with a resin layer A in a B-stage state on the copper foil, and B on the PET film A PET film for press bonding provided with the resin layer A in a stage state was produced.

<D50>
Take a small amount of the conductive powder used in the examples and comparative examples in a beaker, add a few drops of 3% Triton X solution (manufactured by Kanto Chemical Co., Inc.), and blend into the powder. 50 mL of a solution (manufactured by San Nopco) was added, and then a dispersion treatment was performed for 2 minutes using an ultrasonic disperser TIPφ20 (manufactured by Nippon Seiki Seisakusho) to prepare a measurement sample. The volume accumulation standard D50 of this measurement sample was measured using a laser diffraction / scattering particle size distribution analyzer MT3300 (manufactured by Nikkiso).

<Measurement of circularity>
Add the conductive powder (silver-coated copper powder) used in the examples and comparative examples to the solution in which glycerin and methanol are mixed, and mix them into the particle size / shape analyzer “PITA-1” manufactured by Seishin Co., Ltd. 3,000 particles analyzed with analysis software, average circularity, cumulative 10% circularity (shown as “cumulative 10%” in the table), cumulative 50% circularity (in the table “ "Cumulative 50%"), cumulative 90% circularity (shown as "Cumulative 90%" in the table), and circularity standard deviation.
The cumulative 10% circularity, the cumulative 50% circularity, and the cumulative 90% circularity each have a cumulative number ratio (%) of particles counted from the higher circularity (true sphere 1.0) to the lower circularity. It is a value indicating the circularity when reaching%, 50%, and 90%.

Here, the “circularity” is a shape index related to the projected image of the particle proposed by Wadell, and is represented by “circularity” = “circumference of a circle having the same projected area” / “peripheral length of the particle”.
The “peripheral length of a circle having the same projected area” refers to the circumference of a circle equal to the area obtained by obtaining the area when a certain particle is observed from directly above.

<Measurement of resin flow>
The copper foil for press bonding obtained in Examples and Comparative Examples, that is, the copper foil for press bonding provided with the resin layer A in the B stage state on the copper foil was cut into 10 cm squares, and the mass was measured (mass A). . And the cut copper foil for press bonding was pinched | interposed with the SUS board, and 180 degreeC * 10min press was implemented by the normal pressure by the pressure of 14 kgf / cm < ² >. Thereafter, the paste protruding from the 10 cm square was removed, and the mass was measured again (mass B).
After mass measurement, the resin flow (14 kgf / cm ² , 180 ° C.) is calculated using
) Was calculated.
Resin flow (%) = {(mass B-mass C)) / (mass A-mass C)} × 100
The mass C is the mass of a 10 cm square copper foil.

<Vacuum press processing (groove filling)>
A copper foil for press bonding obtained in Examples and Comparative Examples, that is, a copper foil for press bonding provided with a resin layer A in a B-stage state on the copper foil, a lattice pattern having a groove of 200 μm, a depth of 1000 μm, and a groove pitch of 5 mm A laminated body is formed by laminating the resin layer A on the glass epoxy substrate on which the substrate is formed. Further, the laminated body is sandwiched between SUS plates, and pressed at 180 ° C. for 60 minutes in a vacuum at a pressure of 30 kg / cm ^2. did.
Thereafter, the filling state of the groove was determined visually, and the amount of the molten resin (paste) that protruded from the sheet edge was measured to determine “excess”.

Regarding “groove filling”, when the groove is completely filled with resin, it is judged as “good (good)”, and when there is a part not filled with resin in the groove, “× (poor ) ”.
Regarding “excess”, the case where the width of the molten resin (paste) protruding from the sheet edge was less than 10 mm was determined as “good”, and the case where the width was 10 mm or more was determined as “x (poor)”.

<Vacuum press treatment (resistance measurement)>
The PET film for press bonding obtained in the examples and comparative examples, that is, the PET film for press bonding provided with the resin layer A in the B stage state on the PET film, is laminated on the release film with the resin layer A facing up. It was set as the laminated body, this laminated body was pinched | interposed with the SUS board, and 180 degreeC * 60min press was implemented in the vacuum with the pressure of 30 kg / cm < ² >. Thereafter, the release film was peeled off, and the resistance of the resin layer A was measured for surface resistance by a four-probe method (based on JISK7194). Further, the thickness of the cured product was measured, and the specific resistance (Ω · cm) was calculated.

<Comprehensive judgment>
When the specific resistance is less than 10 ⁻⁴ Ω · cm and the evaluation of “groove filling” and “extrusion” is “good”, it is comprehensively judged as “good”. The case where even one item was not satisfied was comprehensively determined as “× (poor)”.

(Discussion)
In any case in Example 1-6, the resin of the resin layer A covers the mold resin portion, and the resin and the conductive powder particles penetrate into every corner in the cut groove formed by half dicing. The inside of the groove was filled with resin, and conduction could be obtained.
From the results of these examples and the test results conducted by the inventors so far, the circularity (cumulative 50%) of the conductive particles in the resin layer A is 0.8 or more, and the resin layer A The conductive particles so that the circularity (cumulative 90%) of the conductive particles therein is 0.6 or more and the standard deviation of the circularity of the conductive particles in the resin layer A is 0.140 or less. It was found that the resin or conductive particles of the resin layer A can be filled up to every corner of the narrow groove or small hole by defining the shape of.

Claims (5)

A metal foil for press bonding comprising a metal foil and a resin layer A containing conductive particles in a B-stage resin,
The conductive particles in the resin layer A have a circularity (referred to as “cumulative 50%”) of 0.80 or more in the cumulative number of particles counted from the higher circularity of the conductive particles A (referred to as “cumulative 50%”), and the resin The conductive particles in the layer A have a circularity (referred to as “cumulative 90%”) of the conductive particles at a frequency accumulation of 90 number% counted from the higher circularity among the conductive particles, and the resin layer The standard deviation of the circularity of the conductive particles in A is 0.140 or less,
The content of conductive particles in the resin layer A is 75 wt% or more ,
A resin foil for press bonding, wherein the resin flow of a resin layer A containing conductive particles in a B-stage resin is 3 to 20% .   The metal foil for press bonding according to claim 1, wherein the thickness of the resin layer A is 1 μm to 500 μm. The metal foil for press bonding according to claim 1 or 2 , comprising a configuration in which the surface of the metal foil opposite to the side on which the resin layer A is located is subjected to an antioxidant treatment. The resin layer A of the metal foil for press bonding according to any one of claims 1 to 3 is superimposed on a circuit board, and heated and pressed, whereby the resin layer A is placed in a groove or hole provided in the circuit board. The metal foil for press bonding according to any one of claims 1 to 3 , which can be filled with resin and conductive particles. The electronic component package formed using the metal foil for press bonding in any one of Claims 1-4 .

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