JP3722096B2 - Mounting board manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a mounted substrate capable of preventing mounting-related defects due to voids inside the active resin adhesive in the manufacturing of a double-sided substrate wherein an active resin adhesive is used. <P>SOLUTION: In this method for manufacturing a mounted substrate wherein the first side and the second side of a substrate are mounted with electronic components, respectively, a soldering paste containing an active thermosetting resin having a thermosetting temperature T3 which is higher than a solder melting point T2 is applied, but only to the second side to be processed at a later stage. This active soldering paste is heated only in a second reflow for the second side, and this prevents mounting-related defects due to voids inside the active resin adhesive. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mounting board manufacturing method for manufacturing a mounting board by mounting electronic components on the board.
[0002]
[Prior art]
As a method for mounting an electronic component such as a semiconductor chip, a solder bonding method is widely used. As a soldering method, a method in which a thermosetting resin adhesive is applied on the electrodes of the substrate in advance before mounting the components is adopted. In this method, the solder bump of the electronic component is landed on the electrode and then the substrate is heated, so that the solder bonding between the solder bump and the electrode and the thermosetting of the resin adhesive are performed in the same heating process. This method has an advantage that it is not necessary to provide the reinforcing underfill resin forming step as an independent step.
[0003]
[Problems to be solved by the invention]
However, in the case where the electronic component mounting method using the resin adhesive is applied to a double-sided mounting board on which electronic components are mounted on both the front and back surfaces, there may be inconveniences as described below. . As described above, in this mounting method, the solder bonding between the solder bump and the electrode and the thermosetting of the resin adhesive are performed in the same heating process. The electronic component on the surface is heated again in the second heating step for the second surface side after the resin is heated in the first heating step for the first surface side.
[0004]
At this time, when a void is formed inside the resin adhesive of the electronic component on the first surface side by the gas generated from the substrate in the first heating step, there is a problem that the void is reheated. Prone to occur. For example, when the gas in the void is peeled off due to expansion by reheating, or when the void is generated close to the joint, the solder in the joint melts during reheating and flows into the void. As a result, poor conduction at the junction may occur. In addition, due to such a problem, there is a case where the mounting quality is deteriorated.
[0005]
Therefore, the present invention provides a mounting substrate manufacturing method capable of preventing a mounting defect caused by a void inside the resin adhesive in manufacturing a mounting substrate performed on a double-sided mounting substrate using a resin adhesive. The purpose is to provide.
[0006]
[Means for Solving the Problems]
The method of manufacturing a mounting board according to claim 1 is a manufacturing method of a mounting board for manufacturing a mounting board in which electronic components are respectively mounted on a first surface of the substrate and a second surface on the back side of the first surface. A first paste supplying step of supplying a solder bonding paste not including a thermosetting resin to the first surface to be mounted first in the mounting step, and mounting an electronic component on the first surface after supplying the paste A first mounting step for landing a connection electrode for a component on the first electrode provided on the first surface, and heating the substrate after the first mounting step to solder the connection electrode to the first electrode A first heating step, a second paste supplying step of supplying a solder bonding paste containing the thermosetting resin to the second surface of the substrate on which mounting of the first surface is completed, and electrons on the second surface after supplying the paste A component is mounted and the connection electrode for the electronic component is provided on the second surface. A second mounting step for landing on the second electrode, and the substrate after the second mounting step is heated to melt the connection electrode or the bonding solder portion supplied in advance to the second electrode. And a second heating step for starting thermosetting of the thermosetting resin.
[0007]
A mounting substrate manufacturing method according to a second aspect is the mounting substrate manufacturing method according to the first aspect, wherein, in the first heating step, the substrate is heated to a temperature equal to or higher than a heating temperature in the second heating step.
[0008]
The mounting board manufacturing method according to claim 3 is the mounting board manufacturing method according to claim 1, wherein the second surface to be mounted later in the component mounting process is for solder bonding including a thermosetting resin. The second paste supply surface to which the paste is supplied is set in advance, and the electronic component to which the mounting method using the thermosetting resin is applied is preferentially used as the second surface in the electronic component arrangement at the time of board design. Deploy.
[0009]
The mounting substrate manufacturing method according to claim 4 is the mounting substrate manufacturing method according to claim 1 , wherein the types of electronic components respectively mounted on the front and back surfaces of the first surface and the second surface of the substrate are as follows: The surface where the proportion of electronic components to which the mounting method using the thermosetting resin can be applied is compared is set as the second surface to be mounted later in the component mounting process.
[0010]
According to the present invention, the solder bonding paste containing the thermosetting resin as a kind is supplied only to the second surface to be mounted later, and the heating of the solder bonding paste is performed for the second surface. By limiting to only one step, it is possible to prevent a mounting failure caused by a void inside the resin adhesive.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIGS. 1 and 2 are process explanatory views of a mounting substrate manufacturing method according to an embodiment of the present invention, and FIG. 3 is a graph showing a temperature profile of a reflow process in the mounting substrate manufacturing method according to an embodiment of the present invention. is there. In this embodiment, a process of manufacturing a mounting substrate by mounting electronic components on a substrate having electrodes formed on both sides by solder bonding is shown.
[0012]
In FIG. 1A, reference numeral 1 denotes a substrate for double-sided mounting. On the first surface 1a (upper surface in FIG. 1) of the substrate 1 and the second surface 1b on the back side of the first surface (lower surface in FIG. 1), An electrode 2 as a first electrode and an electrode 3 as a second electrode are formed. The first surface 1a is a surface to be mounted first in the process of manufacturing a mounting substrate by mounting electronic components on both front and back surfaces of the substrate 1.
[0013]
As shown in FIG. 1A, a cream solder 4 as a solder bonding paste is supplied by printing on an electrode 2 as a first electrode formed on the first surface 1a (first paste supplying step). ). The cream solder 4 contains solder particles in a paste-like flux and is a bonding material intended only for solder bonding. Therefore, the thermosetting property as included in the resin adhesive 6 described later is used. The resin is not included.
[0014]
Next, as shown in FIG. 1 (b), on the first surface 1a after the supply of the cream solder, electronic components 5 having terminals 5a as connection electrodes provided on both ends are mounted (first mounting step). As a result, the terminal 5 a is landed on the electrode 2 via the cream solder 4. Thereafter, the substrate 1 is sent to the reflow process for the second surface reflow intended for the first surface 1a. Here, heating is performed according to a predetermined heating profile (first heating step).
[0015]
The heating profile in the first surface reflow will be described with reference to FIG. When heating is started, the substrate 1 is heated to a preheating temperature T1 lower than the solder melting point temperature T2, and held at this temperature for a predetermined time. Then, after preheating, when the temperature further rises and exceeds the solder melting point temperature T2, the solder component in the cream solder 4 is melted, and the terminal 5a is soldered to the upper surface of the electrode 2 through the molten solder. The solder melting point temperature is 183 ° C. for Sn / Pb solder and 220 ° C. for Sn / Ag solder. In this solder bonding, since the oxide film formed on the surface of the terminal 5a is removed by the flux component in the cream solder 4, good bonding properties are ensured.
[0016]
Thereafter, the heating temperature further rises and reaches a maximum heating temperature Ta set to a temperature lower than the heat resistant temperature T4 (about 250 ° C.). After maintaining this temperature for a predetermined time, the temperature gradually decreases. Here, when the maximum heating temperature Ta is set higher than the maximum heating temperature Tb in the second surface reflow described later, moisture and organic gas contained in the substrate 1 are reduced as much as possible by heating during the first surface reflow. It is preferable because it can be released from the surface. In this case, the maximum heating temperature Ta is about 230 ° C to 240 ° C. When the first surface is reflowed, there is a space through which gas passes on the lower surface of the electronic component 5, so that mounting defects due to voids inside the resin adhesive do not occur.
[0017]
Subsequent to mounting on the first surface 1a, mounting on the second surface 1b is performed. That is, as shown in FIG. 2A, around the electrode 3 on the second surface 1b, a resin adhesive 6 that is a solder bonding paste is supplied so as to cover the electrode 3 by the dispenser 7 (second paste). Supply process). The resin adhesive 6 is an adhesive function that seals and reinforces the lower surface of an electronic component by containing an active component having an oxide film removing ability in a base material mainly composed of a thermosetting resin such as an epoxy resin. In addition to this, the oxide film on the surface of the solder is removed at the time of soldering to serve as a flux that improves solderability. Since the resin adhesive 6 removes the oxide film on the surface of the solder bump by the active component contained therein, it is not necessary to apply a separate flux, and the cleaning process after reflow required in the conventional method using the flux is omitted. It has the advantage of being able to.
[0018]
Here, the base has a thermosetting temperature higher than the melting point of the solder used for mounting. In addition, the thermosetting temperature as used in this Embodiment is the temperature calculated | required by the differential scanning calorimetry (DSC) used for the measurement of the hardening reaction of a resin material. That is, if the relationship between the amount of heat and temperature obtained in the process of heating a 10 mg sample at a temperature rising rate of 10 ° C./min is plotted and plotted with the amount of heat on the vertical axis and the temperature on the horizontal axis, Is formed. Then, a tangent line is drawn from the inflection point on the slope on the high temperature side of this mountain-shaped curve, and the temperature at which this tangent line intersects the horizontal axis is determined as the thermosetting temperature.
[0019]
Next, as shown in FIG. 2C, an electronic component 8 having a solder bump 9 as a connection electrode provided on the lower surface is mounted on the second surface 1b after the resin adhesive is supplied (second mounting step). Thus, the solder bump 9 is landed on the electrode 3 through the resin adhesive 6. At this time, the lower surface of the electronic component 8 is almost completely filled with the resin adhesive 6. And after this, the substrate 1 is sent to the reflow process for the second surface reflow intended for the second surface 1b, wherein the heating according to a predetermined heating profile are (second heating step).
[0020]
The heating profile in the second surface reflow is substantially the same as that in the first surface reflow as shown in FIG. 3. When the temperature rises and exceeds the solder melting point temperature T2, the solder bump 9 is melted and the molten solder is removed. The terminal 5a is solder-bonded to the electrode 3 through the via. Here, the solder bumps 9 serve as connection electrodes for connecting the electronic component 8 to the substrate 1 and also serve as bonding solder portions supplied to the connection electrodes. In this solder bonding, even when an oxide film is generated on the surface of the electrode 3 by heating at the time of the first reflow, the oxide film is removed by the active component in the resin adhesive 6 to ensure good solderability. Is done.
[0021]
Thereafter, the heating temperature further rises and reaches a maximum heating temperature Tb set to a temperature higher than the thermosetting temperature T3 and lower than the heat-resistant temperature T4. After maintaining this temperature for a predetermined time, the temperature gradually decreases. Here, the maximum heating temperature Tb is lower than the maximum heating temperature Ta in the first surface reflow as described above.
[0022]
Further, this heating causes the thermosetting reaction of the resin adhesive 6 to proceed in parallel. However, since the thermosetting temperature T3 of the resin adhesive 6 is higher than the solder melting temperature T2 of the solder bump 9, the solder bump 9 When the molten solder that has melted wets the surface of the electrode 2, the resin adhesive 6 has not yet started thermosetting. Therefore, the flow of the molten solder in the resin adhesive 6 is ensured, and the self-alignment between the solder bump 9 and the electrode 3 is not hindered.
[0023]
Then, after the molten solder is joined to the electrode 3, the heating is continued and the temperature rises. Then the temperature was raised to a maximum heating temperature T b exceeds the thermosetting temperature T3, the process proceeds to temperature lowering process after the temperature has been maintained for a predetermined time. In this heating process, the thermosetting of the resin adhesive 6 proceeds rapidly during the time t during which the temperature is maintained at the thermosetting temperature T3 or higher. Thereby, mounting of the electronic component 5 on the second surface 1 b is completed.
[0024]
In the second surface reflow, since it has already been heated at a high temperature by the first surface reflow as described above, most of the organic components and moisture contained in the substrate 1 are gasified by heating from the surface. It is discharged, and the generation of voids due to the confinement of these gases in the resin adhesive 6 is small. In addition, even when a void is generated, the resin adhesive 6 is not further heated to a higher temperature thereafter, so that a problem that occurs when the void is reheated, for example, the gas in the void is regenerated. Such as peeling of resin due to expansion due to heating, and poor conduction of the joint resulting from melting the solder at the time of reheating when voids are generated in the vicinity of the joint. There is no occurrence.
[0025]
The manufacturing method of the mounting substrate described in the above embodiment is applied in the following two ways in production. In the first aspect, in the design stage of the mounting substrate on which the electronic components are mounted on both sides, the first surface of the electronic component is taken into consideration in consideration of the applicability of the resin adhesive 4 to the electronic component to be mounted. The distribution to the second surface is determined.
[0026]
That is, when designing a mounting board for manufacturing a mounting board in which electronic components are mounted on the first surface of the substrate and the second surface on the back side of the first surface, the second target to be mounted later in the component mounting process. The surface is set in advance as a second paste supply surface to which the soldering paste including the resin adhesive 6 is supplied. And in the electronic component arrangement | positioning at the time of board design, the electronic component to which the mounting system using a thermosetting resin is applied is preferentially arrange | positioned on a 2nd surface. By arranging electronic components according to such a policy at the time of designing the board, electronic components using the resin adhesive 6 are concentratedly arranged on the second surface to be mounted later. Therefore, the situation where the used resin adhesive 6 goes through two thermosetting processes does not occur.
[0027]
On the other hand, the following handling is performed about the board | substrate which is not considered as mentioned above in the board | substrate design process. First, when the electronic component arrangement of the double-sided mounting board is presented, the type and quantity of the electronic parts mounted on the front and back surfaces of the board are compared. Then, the surface with the higher proportion of electronic components to which the mounting method using the resin adhesive 6 can be applied is set as a second surface to be mounted later in the component mounting process, and the resin bonding is performed on such electronic components. A mounting method using the material 6 is applied.
[0028]
A mounting method that does not use the resin adhesive 6 such as a mounting method using cream solder is applied to the other electronic components on the second surface and the electronic components on the first surface. As a result, the electronic component using the resin adhesive 6 is disposed only on the second surface to be mounted later, and thus the situation where the used resin adhesive 6 undergoes two thermosetting processes does not occur.
[0029]
【The invention's effect】
According to the present invention, a solder bonding paste having an active action of removing a solder oxide film only on a second surface to be mounted later and including a thermosetting resin as a type is supplied. Since the heating is limited to one time of the second heating process for the second surface, mounting defects caused by voids inside the resin adhesive can be prevented.
[Brief description of the drawings]
FIG. 1 is a process explanatory diagram of a mounting substrate manufacturing method according to an embodiment of the present invention. FIG. 2 is a process explanatory diagram of a mounting substrate manufacturing method according to an embodiment of the present invention. Graph showing temperature profile of reflow process in manufacturing method of mounting substrate of embodiment
DESCRIPTION OF SYMBOLS 1 Board | substrate 1a 1st surface 1b 2nd surface 2, 3 Electrode 4 Cream solder 5 Electronic component 5a Terminal 6 Resin adhesive 8 Electronic component 9 Solder bump

Claims (4)

A mounting substrate manufacturing method for manufacturing a mounting substrate in which electronic components are respectively mounted on a first surface of a substrate and a second surface on the back side of the first surface, the first surface being a mounting target first in the component mounting step In addition, a first paste supplying step of supplying a solder bonding paste that does not contain a thermosetting resin, and an electronic component is mounted on the first surface after the paste is supplied, and an electrode for connecting the electronic component is provided on the first surface. A first mounting step of landing on the first electrode, a first heating step of heating the substrate after the first mounting step and soldering the connection electrode to the first electrode, and mounting of the first surface A second paste supplying step of supplying a solder bonding paste containing the thermosetting resin to the second surface of the completed substrate, and mounting an electronic component on the second surface after supplying the paste to provide an electrode for connecting the electronic component Second mounting step of landing on the second electrode provided on the second surface Then, the substrate after the second mounting step is heated to melt the connecting electrode or the bonding solder portion supplied in advance to the second electrode to solder the connecting electrode to the second electrode and to perform the thermosetting. And a second heating step for initiating thermosetting of the functional resin. The method for manufacturing a mounting substrate according to claim 1, wherein in the first heating step, the substrate is heated to a temperature equal to or higher than a heating temperature in the second heating step. The second surface comprising a mounting object after the component mounting process, set in advance as the second paste supply plane solder bonding paste containing a thermosetting resin is supplied in an electronic component arrangement of a board design, The method for manufacturing a mounting board according to claim 1, wherein electronic components to which a mounting method using the thermosetting resin is applied are preferentially arranged on the second surface. Compare the type and quantity of electronic components mounted on the front and back surfaces of the first and second surfaces of the board, respectively, and the proportion of electronic components to which the mounting method using a thermosetting resin can be applied is larger. 2. The method of manufacturing a mounting board according to claim 1, wherein the surface is set as a second surface to be mounted later in the component mounting process.

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