JP2013171927A - Method of manufacturing electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an electronic apparatus which can ensure excellent connection strength and connection resistance, when connecting the electrode of an electronic component with the electrode of a circuit board.SOLUTION: A conductive adhesive 30 contains 1.5-3.9 wt% of reductant, i.e., 8-quinolinol, relative to the whole conductive adhesive; a high melting point metal, and a low melting point metal having a melting point lower than that of the high melting point metal and higher than that of the reductant. The method of manufacturing an electronic apparatus includes a step for bringing an electrode 21 of an electronic component 20 into contact with an electrode 11 of a circuit board 10 via the conductive adhesive 30, a step for melting the low melting point metal by heating the conductive adhesive 30 at a temperature equal to or higher than 180°C and equal to or higher than the melting point of the low melting point metal, and a step for completing hardening of a thermosetting resin by lowering the temperature subsequently.

Description

  The present invention relates to an electronic device manufacturing method.

  Patent Document 1 discloses a method for manufacturing an electronic device in which an electrode of an electronic component and an electrode of a circuit board are electrically connected via a conductive adhesive formed by blending a conductive filler and a thermosetting resin. Is a conductive adhesive at a high temperature of 180 ° C. or higher using a high melting point metal such as Ag and a low melting point metal such as Bi or In as the conductive filler. Is heated to melt the low melting point metal, and then the curing of the thermosetting resin is completed.

  Patent Document 2 discloses that a conductive adhesive comprising a conductive filler and a resin contains AgSn as a conductive filler, and further includes 8-hydroxyquinoline (8-HQL, 8- Those containing quinolinol are also described. This 8-quinolinol functions as a reducing agent. In addition, in the Example of patent document 2, the heating temperature of the conductive adhesive containing 8-HQL is 150 degreeC.

JP 2005-89559 A JP 2006-225426 A

  By the way, the inventors of the present application actually made an electronic component whose surface of the electrode is made of Sn and a conductive adhesive containing AgSn, which is a high melting point metal, and In, which is a low melting point metal, as in Patent Document 1. Used to bond the electrode of the electronic component and the electrode of the circuit board, heat the conductive adhesive at a high temperature of 180 ° C or higher to melt the low melting point metal, and then complete the curing of the thermosetting resin Then, when the electronic device was manufactured, the connection resistance between the electrode of the electronic component and the electrode of the circuit board was higher than the target value, and further reduction of the connection resistance was necessary.

  For this reason, in order to investigate the possibility of further reduction in connection resistance, the circuit board after bonding and the electronic component were analyzed, and it was found that an oxide film was formed on the surface of the electrode of the electronic component.

  Therefore, if the reducing agent (8-quinolinol) described in Patent Document 2 is added to the conductive adhesive, the oxide film on the surface of the electronic component electrode and the like can be removed by the reducing action of the reducing agent, and the connection resistance can be further increased. It is considered that a decrease is possible.

  However, actually, when a reducing agent (8-quinolinol) is blended in the conductive adhesive and the electrodes of the electronic component and the circuit board are bonded in the same manner as described above, the heating of the conductive adhesive is performed. Since the temperature is 180 ° C. or higher and higher than the temperature described in Patent Document 2, voids (voids) due to evaporation of the reducing agent are likely to occur in the conductive adhesive, and the amount of the reducing agent is too large. It was found that the connection strength was lowered due to the presence of voids. It was also found that if the amount of the reducing agent is too small, the oxide film is not sufficiently removed and the effect of reducing the connection resistance cannot be obtained.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a method for manufacturing an electronic device in which good connection strength and connection resistance are obtained in connection between an electrode of an electronic component and an electrode of a circuit board.

In order to achieve the above object, in the invention described in claim 1,
While preparing an electronic component (20) and a circuit board (10), 8-quinolinol which is a reducing agent (32) is used as the conductive adhesive (30) in an amount of 1.5 to 3.9 wt% of the entire conductive adhesive. And a step of preparing a high melting point metal (34) as a conductive filler and a low melting point metal (33) having a melting point lower than that of the high melting point metal and higher than that of the reducing agent.
Contacting the electrode (21) of the electronic component (20) and the electrode (11) of the circuit board (10) via the conductive adhesive (30);
Heating the conductive adhesive (30) at a temperature not lower than 180 ° C. and not lower than the melting point of the low melting point metal (33) to melt the low melting point metal (33);
Thereafter, the temperature is lowered to complete the curing of the thermosetting resin (31).

  As described above, the conductive adhesive containing the thermosetting resin (31), the high melting point metal (34), and the low melting point metal (33) and containing 1.5 to 3.9 wt% of 8-quinolinol is used. After heating the conductive adhesive (30) at a temperature of 180 ° C. or higher to melt the low melting point metal (33), the thermosetting resin (31) is completely cured, so that the electrodes and circuits of the electronic component Good connection resistance and connection strength can be obtained in connection with the electrodes of the substrate.

  The invention according to claim 1 is particularly effective in the case of the heating temperature as in the inventions according to claims 2 and 3.

  That is, in the invention described in claim 2, the high melting point metal (34) is AgSn, the low melting point metal (33) is In, and the heating temperature in the step of melting the low melting point metal (33) is AgSn. It is characterized by having a melting point or higher.

  According to a third aspect of the present invention, the heating temperature in the step of melting the low melting point metal (33) is equal to or higher than the melting point of Sn or Sn alloy constituting the surface of the electrode (21) of the electronic component (20). It is characterized by being.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

It is a schematic sectional drawing of the electronic device in one Embodiment of this invention. It is a figure which shows the profile of the heating temperature in the resin hardening process in one Embodiment of this invention. It is a schematic diagram which shows the state of the conductive adhesive 30 and the component electrode 21 when it heats with the profile of FIG. It is a figure which shows the relationship between the compounding quantity of a reducing agent, and connection resistance value. It is a figure which shows the relationship between the compounding quantity of a reducing agent, and connection strength.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an electronic device 1 according to an embodiment.

  As shown in FIG. 1, the electronic component 20 is mounted on the circuit board 10, and the electrode 11 of the circuit board 10 and the electrode 21 of the electronic component 20 are electrically connected via a conductive adhesive 30. . Hereinafter, the electrode 11 of the circuit board 10 is referred to as a substrate electrode 11, and the electrode 21 of the electronic component 20 is referred to as a component electrode 21.

  As the circuit board 10, a ceramic board (for example, a laminated alumina board or a thick film board), a printed board (resin board), or the like can be used.

  The substrate electrode 11 is formed on one surface of the circuit board 10, and includes, for example, Ag-based metals such as Ag (silver), AgSn (silver and tin alloy), and AgPd (silver and palladium alloy), Cu (copper), and the like. ) And CuNi (alloy of copper and nickel), a thick film or plating using a material such as Cu-based metal, Ni-based metal, or Au (gold). In the example shown in FIG. 1, a ceramic substrate is used as the circuit substrate 10, and the substrate electrode 11 has an electrode structure in which an Au plating layer 13 is formed on a Cu plating layer 12.

  As the electronic component 20, a surface mount component such as a capacitor, a resistor, a coil, a crystal resonator, a thermistor, and other semiconductor elements can be employed. In the example shown in FIG. 1, a chip capacitor is used as the electronic component 20.

  The component electrode 21 is made of Sn or an Sn alloy whose surface is at least a base metal. In the example shown in FIG. 1, the component electrode 21 is made of Cu / Ni / Sn, and the surface of the component electrode 21 is made of Sn plating.

  Next, a method for manufacturing the electronic device 1 in which the component electrode 21 of the electronic component 20 and the substrate electrode 11 of the circuit board 10 are electrically connected via the conductive adhesive 30 will be described.

  First, the circuit board 10 on which the substrate electrode 11 is formed and the electronic component 20 on which the component electrode 21 is formed are prepared, and a conductive adhesive 30 is prepared (preparation process).

  The conductive adhesive 30 is formed by blending a conductive filler and a thermosetting resin. In the present embodiment, the conductive adhesive 30 contains 8-quinolinol as a reducing agent as the conductive adhesive 30 and is conductive. A material containing a high melting point metal and a low melting point metal as a filler is prepared.

  8-Quinolinol is represented by the following formula (I) and has a melting point of 76 ° C.

８−キノリノールの含有量は、後述する実施例および比較例からわかるように、導電性接着剤全体に対して１．５〜３．９ｗｔ％の範囲内とする。

The content of 8-quinolinol is within the range of 1.5 to 3.9 wt% with respect to the entire conductive adhesive, as can be seen from Examples and Comparative Examples described later.

  The high melting point metal is a metal whose melting point is higher than that of the low melting point metal. Examples of the refractory metal include Ag, AgSn, Cu, and Ni. However, when melting together with the Sn plating layer on the surface of the component electrode 21 by heating in the resin curing step described later, it is preferable to use a metal having a melting point of Sn or lower as the high melting point metal. It is preferable to use AgSn whose composition (component ratio) is set so as to be equal to or lower than the melting point. Further, the refractory metal may not be melted by heating in the resin curing step described later.

  The low melting point metal is a metal whose melting point is lower than that of the high melting point metal and higher than that of the reducing agent. Examples of the low melting point metal include simple substances such as In and Bi and alloys containing In and Bi.

  Moreover, as a thermosetting resin, what hardens | cures at the temperature of about 100 to 200 degreeC is used. As such a thermosetting resin, an epoxy resin, a silicone resin, a polyimide resin, a urethane resin, an acrylic resin, or the like can be used. In particular, an epoxy resin is useful because it has a relatively small curing shrinkage and a high adhesive force.

  Then, the component electrode 21 and the substrate electrode 11 are brought into contact with each other through the conductive adhesive 30 (contact process). Specifically, in this contact step, the conductive adhesive 30 is supplied onto the substrate electrode 11 of the circuit board 10 by mask printing or dispensing (conductive adhesive supply step).

  Subsequently, the electronic component 20 is mounted on the circuit board 10 in a state where the substrate electrode 11 and the component electrode 21 are aligned (component assembly step).

  Thereafter, the conductive adhesive 30 is heated to cure the thermosetting resin 31 (resin curing step). The resin curing step includes heating the conductive adhesive 30 at a temperature of 180 ° C. or higher and a melting point of the low melting point metal to melt at least the low melting point metal (metal melting step), and then the metal melting step. The process is divided into a process of lowering the temperature and completing the curing of the thermosetting resin (resin curing completion process).

  Here, FIG. 2 shows an example of a heating temperature profile (heating profile) in the resin curing step. This heating profile can be realized by using a heating furnace capable of controlling the temperature.

  In the heating profile shown in FIG. 2, the surface of the component electrode 21 is composed of Sn plating, and AgSn having a lower melting point than that of Sn is adopted as the high melting point metal in the conductive adhesive 30, and the low melting point is adopted. This is a case where In is used as the metal and an epoxy resin is used as the thermosetting resin in the conductive adhesive 30.

  In the heating profile shown in FIG. 2, the temperature is increased from room temperature to the peak temperature at a temperature increase rate of 50 ° C./min to 500 ° C./min, and held at the peak temperature for 40 to 80 seconds (metal melting step). This peak temperature is not lower than the melting point of Sn (232 ° C.) and not higher than the heat resistance temperature of the electronic component (for example, 250 ° C. or lower). Then, the temperature is lowered from the peak temperature by stopping the heating furnace (resin curing completion step).

  3A to 3D show the state of the conductive adhesive 30 and the component electrode 21 when heated with the heating profile of FIG.

  As shown in FIG. 3A, the component electrode 21 includes a Cu layer, a Ni layer 22, and a Sn plating layer 23 (not shown) as shown in the example shown in FIG. In the state before heating, an oxide film 24 is formed on the surface of the Sn plating layer 23.

  As shown in FIG. 2, in the metal melting step, when the temperature rises from room temperature, the resin viscosity decreases, the thermosetting resin 31 in the conductive adhesive 30 gels, and the heating temperature becomes the reducing agent (8- When the melting point (76 ° C.) of quinolinol is reached, the reducing agent melts. At this time, as shown in FIG. 3B, the oxide film 24 on the surface of the Sn plating layer 23 is reduced and removed by the molten reducing agent 32 (oxide film removal).

  Furthermore, when the temperature rises and the heating temperature reaches the melting point of In (156 ° C.), the In filler melts. At this time, as shown in FIG. 3C, the In filler 33 is fused to the AgSn filler 34 and the Sn plating layer 23, whereby the AgSn fillers 34 are joined together, and the AgSn filler 34 and the Sn plating layer 23. Are joined (In melting / fusion).

  Further, when the temperature rises and the heating temperature reaches the melting point of AgSn (218 ° C.), the AgSn filler melts, and when the heating temperature reaches the melting point of Sn (232 ° C.), the Sn plating layer 23 melts. At this time, as shown in FIG. 3 (d), the Sn plating layer 23, the AgSn filler 34, and the In filler 33 are alloyed to form a conductive form between the conductive fillers or between the conductive filler and the component electrode ( AgSn, melting of Sn).

  Further, the viscosity of the thermosetting resin 31 increases during the period of holding at the peak temperature.

  Thereafter, in the resin curing completion step, the thermosetting resin 31 is continuously heated at a temperature lower than the peak temperature, and the curing of the thermosetting resin 31 is completed. In this way, the connection between the component electrode 21 and the substrate electrode 11 is completed, and the electronic device 1 shown in FIG. 1 is completed.

  As described above, in the resin curing step of the present embodiment, the temperature is rapidly increased to the peak temperature and held at the peak temperature for a short time, so that the reducing agent 32 can Sn before the thermosetting resin 31 is cured. The oxide film 24 on the surface of the plating layer 23 is removed, and the In filler 33, the AgSn filler 34, and the Sn plating layer 23 of the component electrode 21 are melted and alloyed, and then the curing of the thermosetting resin 31 is completed.

  Here, as described in the column of the problem to be solved by the invention, since the peak temperature in the resin curing step of this embodiment is higher than the heating temperature (150 ° C.) described in Patent Document 2, the conductive adhesion is performed. Voids (voids) due to vaporization of the reducing agent 32 are likely to occur in the agent 30. For this reason, when there are too many compounding quantities of the reducing agent 32, the reducing agent 32 which remained in the thermosetting resin 31 vaporizes and remains as a void, and the connection area of the component electrode 21 and the board | substrate electrode 11 reduces, Connection strength is reduced.

  Moreover, when there are too few compounding quantities of the reducing agent 32, the oxide film 24 on the surface of Sn plating layer 23 will not fully be removed, but the fall effect of connection resistance will not be acquired.

  On the other hand, according to the present embodiment, by setting the blending amount of the reducing agent 32 to 1.5 to 3.9 wt%, in the connection between the component electrode 21 and the substrate electrode 11, good connection resistance and connection Strength can be obtained.

  FIG. 3B shows a state in which the oxide film 24 on the surface of the Sn plating layer 23 is removed by the molten reducing agent 32, but not only the oxide film 24 on the surface of the Sn plating layer 23. Further, the AgSn filler 34, the In filler 33, and the oxide film formed on the surface of the substrate electrode are also removed.

  In the heating profile of FIG. 2, the resin curing completion process was performed by stopping the heating furnace maintained at the peak temperature and performing heating by the residual heat of the heating furnace, but if it is within a temperature range lower than the peak temperature Heating control may be performed. For example, the temperature may be maintained at a predetermined temperature for a certain time, or the rate of temperature decrease may be slower than when the heating furnace is stopped.

  In the heating profile of FIG. 2, the peak temperature is set to the melting point of Sn (232 ° C.) or more in order to melt the AgSn filler 34 and the Sn plating layer 23, but the AgSn filler 34 and the Sn plating layer 23 are not melted. The peak temperature may be changed to another temperature as long as at least the low melting point metal can be melted. For example, the peak temperature may be lower than the melting point of Sn and higher than the melting point of AgSn (a high melting point metal whose melting point is lower than the melting point of Sn). The peak temperature may be a temperature lower than the melting point of AgSn (high melting point metal whose melting point is lower than the melting point of Sn) and higher than the melting point of In (low melting point metal). It is good also as temperature below ° C.

  In the above-described embodiment, in the resin curing step, the conductive adhesive 30 is heated at a temperature equal to or higher than 180 ° C. and equal to or higher than the melting point of the low melting point metal. If it is a temperature of 158 ° C. or higher, it may be heated at a temperature of less than 180 ° C.

  As shown in FIG. 1, the conductive adhesive having the following material composition is used to bond the substrate electrode 11 of the circuit board 10 and the component electrode 21 of the electronic component 20, and then the connection of the conductive adhesive 30. Resistance value and connection strength were measured. The configurations of the substrate electrode 11 and the component electrode 21 are as described above.

  The conductive adhesive used was bisphenol F type epoxy resin (main agent), biphenyl type epoxy resin (main agent), trifunctional epoxy resin (main agent) and phenol resin (curing agent) as thermosetting resin, and conductive filler. As a filler, AgSn filler (high melting point metal) and In filler (low melting point metal) and 8-quinolinol as a reducing agent are included. In the AgSn filler, the composition of the AgSn alloy is set so that the melting point is 218 ° C.

  In Examples 1 to 7, the blending amount of each material is 85 wt% of the total conductive filler, 1.5 to 3.9 wt% of the reducing agent, and the remainder is thermosetting with respect to the entire conductive adhesive. Resin was used.

  Moreover, in the comparative example 1, the electroconductive filler total was 85 wt%, the reducing agent was 0%, and the thermosetting resin was 15 wt%. In Comparative Example 2, the total amount of conductive filler was 85 wt%, the reducing agent was 4.5%, and the thermosetting resin was 10.5 wt%.

  In Examples 1 to 7 and Comparative Examples 1 and 2, the breakdown of the total conductive filler of 85 wt% is 80 wt% for the AgSn filler and 5 wt% for the In filler.

  The heating conditions in the resin curing step were as follows: peak temperature: 235 ° C., peak holding time: 1 min, temperature increase rate: 100 ° C./min.

  The connection resistance value was measured by a four-terminal method using a 1608 size capacitor chip. The connection strength was measured using a 1608 size capacitor chip and a shear test.

  4 and 5 show measurement results of connection resistance values and connection strengths in Examples 1 to 7 and Comparative Examples 1 and 2. FIG.

  As shown in FIG. 4, about connection resistance value, when the compounding quantity of 8-quinolinol is 1.5 wt% or more (Examples 1-7, Comparative Example 2), 8-quinolinol is 0 wt% (Comparative Example 1). As compared with the above, the connection resistance value can be lowered to 10 mΩ or less, which is generally desired for in-vehicle devices.

  As shown in FIG. 5, as for the connection strength, as the compounding amount of 8-quinolinol increases, the connection strength decreases compared to when 8-quinolinol is 0 wt% (Comparative Example 1). If the compounding quantity of 8-quinolinol is 3.9 wt% or less (Examples 1-7), the connection strength of 10N or more can be ensured. By the way, according to the knowledge of the present inventors, if the connection strength is 10 N or more, the occurrence of poor connection (separation of adhesive) between the electronic component and the circuit board in the mold sealing process after the resin curing process is prevented. I know I can.

1 Electronic Device 10 Circuit Board 11 Board Electrode (Circuit Board Electrode)
20 Electronic component 21 Component electrode (Electronic component electrode)
30 conductive adhesive 31 thermosetting resin 32 8-quinolinol (reducing agent)
33 In filler (low melting point metal)
34 AgSn filler (high melting point metal)

Claims (3)

The electrode (21) of the electronic component (20) and the circuit board (10) are connected via a conductive adhesive (30) formed by blending the conductive filler (33, 34) and the thermosetting resin (31). In the method of manufacturing an electronic device in which the electrode (11) is electrically connected and the surface of the electrode (21) of the electronic component is made of Sn or Sn alloy,
While preparing the said electronic component (20) and the said circuit board (10), as the said electrically conductive adhesive (30), 8-quinolinol which is a reducing agent (32) is 1.5- of the whole said electrically conductive adhesive. 3.9 wt% and a high melting point metal (34) as the conductive filler and a low melting point metal (33) having a lower melting point than the high melting point metal and a higher melting point than the reducing agent A process to prepare;
Contacting the electrode (21) of the electronic component (20) and the electrode (11) of the circuit board (10) via the conductive adhesive (30);
Heating the conductive adhesive (30) at a temperature not lower than 180 ° C. and not lower than the melting point of the low melting point metal (33) to melt the low melting point metal (33);
Then, the process of lowering temperature and completing the hardening of the said thermosetting resin (31) is performed, The manufacturing method of the electronic device characterized by the above-mentioned. The high melting point metal (34) is AgSn, the low melting point metal (33) is In,
The method for manufacturing an electronic device according to claim 1, wherein the heating temperature in the step of melting the low melting point metal (33) is equal to or higher than the melting point of AgSn. The heating temperature in the step of melting the low melting point metal (33) is equal to or higher than the melting point of Sn or Sn alloy constituting the surface of the electrode (21) of the electronic component (20). The manufacturing method of the electronic device as described in any one of Claims 1-3.

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