JPH0338098A - Resin sealing of electronic component module - Google Patents

Abstract

PURPOSE:To prevent the resin filling the through-hole of a substrate from flowing out of the hole and occurrence of bubbles in the hole by filling one side part of the case divided by a substrate with a resin having a low thixotropic property after enclosing the through-hole with another resin having a high thixotropic property. CONSTITUTION:A hybrid IC 11, etc., formed of electronic components 13-15 mounted on both surfaces of a substrate 12 provided with a through hole 12a formed from surface side to the rear side of the substrate is housed in a case 16 so that the inside of the case 16 can be divided into two parts by means of the substrate 12. Then, after the hole 12a of the substrate 12 is filled with 8 resin 18 having a high thixotropic property, one side part of the inside of the case 16 divided by the substrate 12 is filled with another resin 19 having a low thixotropic property so as to enclose the components 13 and 14 which can be resin enclosed with the resin 19. Therefore, flowing out of the resin 19 from the hole 12a and occurrence of bubbles in the hole 12a can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a hybrid integrated circuit (I) in which electronic components are mounted on a board with through holes formed therein for a double-sided mounting structure.
The present invention relates to a 4mW8 sealing method for an electronic component module, in which the electronic component module such as C is housed inside a case and filled with resin.

Conventional technology An electronic component module in which a plurality of 41 types of electronic components are mounted on both sides of a board is disclosed in, for example, Japanese Patent Application Laid-open No. 6384099@
As shown in the publication, it is generally housed in a case made of metal or hard synthetic resin, and after the board with electronic components mounted on both the front and back is housed in the case. This case is filled with resin to seal the internal space.

The purpose of resin-sealing electronic component modules in this way is to suppress the occurrence of mechanical or thermal stress on the electronic components mounted on the board, as well as to prevent leakage of circuits due to moisture. This has the effect of ensuring the reliability of electronic component modules such as hybrid ICs.

In addition, among various electronic component modules, if electronic components are installed for the purpose of detecting pressure or light, the inside of the case of the electronic component module cannot be completely sealed with resin. There are cases. In other words, if resin is filled near a pressure sensor that detects pressure, or near a photodiode that detects light, for example, the adhesion of resin may fix the movable parts or reduce the amount of light received, thereby impairing its function. There is a risk of damage.

Therefore, in an electronic component module equipped with this type of sensor, etc., it is necessary to avoid filling the vicinity of the pressure sensor or photodiode with resin.

Therefore, electronic components that can be sealed with resin, such as semiconductor elements, and electronic components that must be sealed with resin, such as pressure sensors, are mounted on the same substrate! If it is necessary to do so, mount them separately on both the front and back sides of the board, and when this double-sided mounted board is housed in a case,
This substrate divides the inside of the case into two chambers, and a method is adopted in which resin is filled only on the side of the case on which electronic components that can be sealed with resin are mounted.

For example, FIG. 2 is a cross-sectional view schematically showing a conventional electronic component module of this type. On the one hand (the upper part in FIG. 2) where the circuit pattern of the substrate 1 is formed, there are semiconductor elements, etc. A pressure sensor 3 is mounted on the other side of the substrate 1 as an electronic component that is not sealed with resin II, and each lead of the electronic component 2 is mounted on the other side of the substrate 1. It is electrically connected to the formed circuit pattern via a through hole 1a formed through the substrate 1.

The electronic component module 4, which has electronic components 2 and 3 mounted on both sides of the board 1, is housed in a case 5, and is horizontally arranged so as to divide the interior of the case 5 into two upper and lower chambers, as shown in FIG. The peripheral edge of the substrate 1 is fixed to a protrusion 5a provided on the inner peripheral surface of the case 5 with an adhesive 6.

Moreover, the pressure sensor 3 attached to the lower surface side of the substrate 1 in FIG. Then, the electronic component module 4 housed in the case 5 in this manner is assembled to the substrate 1 by filling the case 5 with filling resin 7 from above as shown in FIG.
Electronic components 2 such as semiconductor elements mounted on the upper surface side of the housing are sealed with 41fJ resin.

Problems to be Solved by the Invention However, in the case of the conventional method described above, since the through hole 1a is formed in the board 1 to enable mounting on both sides, the filling resin 7 filled in the case 5 is If the viscosity is low, charging will occur as shown in Figure 2. The JR resin 7 flows out from this through hole 1a to the bottom side of the board 1, and the case 5
There is a problem in that the filling resin 7 accumulates at the bottom of the pressure sensor 3 and adheres to the pressure sensor 3, obstructing its function as a pressure sensor.

Therefore, filling Ia from the through hole 1a of the substrate 1
In order to prevent the leakage of the I14 fat 7, a method of sealing the I14 fat using a highly viscous filled resin 8 as shown in FIG. 3 has conventionally been adopted.

This method is advantageous in terms of cost, as conventional construction methods can be used as is by simply using a highly viscous filling resin. Due to the high density and high integration of electronic components, the various electronic components mounted in electronic component modules are also becoming smaller.As a result, if a resin with high viscosity is used as the filling resin, the through hole 1 will be damaged due to the high viscosity.
The IIA fat no longer flows out from a, and as shown in FIG. Air bubbles 9 tend to remain on the bottom surface of the electronic component 2, etc.
There was a problem in that the surroundings of these electronic components 2 could not be completely covered.

In this way, when the bubble 9 is formed around the electronic component 2, the bubble 9 portion of the electronic component module 4 and the filled W4
Stress generated due to the difference in coefficient of thermal expansion with the resin 8 portion is repeatedly applied, causing a loss in the reliability of the electronic component module 4. Furthermore, when used under high humidity conditions, water vapor may enter the bubbles 9 and condense, and this moisture may cause electrical malfunctions such as circuit leakage. Preventing the generation of bubbles has become an important problem as the spacing between circuit patterns becomes narrower due to the miniaturization and higher density of electronic components and circuits.

This invention was made in view of the above circumstances, and it is an object of the present invention to reliably prevent the filling resin from flowing out from through holes formed in the board, and to reliably seal only the electronic components mounted on one side of the board. The purpose of the present invention is to provide a method for resin-sealing electronic component modules that enables the following.

Means for Solving the Problems In order to achieve the above-mentioned objects, the resin sealing method of the electronic component module of the present invention provides a hybrid module in which electronic components are mounted on both the front and back surfaces of a substrate provided with through holes extending through the front and back sides. Electronic component modules such as ICs are housed in the case,
In this resin-sealing method for an electronic component module, in which the case is filled with resin and the electronic component module is resin-sealed, the electronic component module is housed in the case so that the inside of the case is divided into two by the board, and The method is characterized in that after the through-holes in the substrate are closed using a highly thixotropic resin, only one of the cases divided by the substrate is filled with a low thixotropic resin.

Effect: According to the method of the present invention, after the through-hole of the board housed in the case so as to divide the case into two chambers is closed using a highly thixotropic resin,
One of the divided substrates in this case is filled with a resin having low thixotropic properties, and only the electronic components that can be sealed 111@ are sealed with the resin. In this way, resin sealing requires a resin with high thixotropinicity and a resin with low [i and 2@
Types of filled resins are used.

The thixotropic property of a resin is that when an external force is applied to the resin, the viscosity decreases and the resin becomes fluid.
When an external force is removed and the material becomes stationary, its viscosity increases and it loses its fluidity, a phenomenon also known as thixotropy.

Therefore, to fill the case with #lli, first, a highly thixotropic resin is injected into the through hole of the circuit board and its vicinity using a syringe, the through hole is closed, and then a resin with low thixotropic property is injected into the through hole and its vicinity. Fill it all over. The resin injected with a syringe has high thixotropic properties, but when it is injected from the syringe, an external force (in this case, discharge pressure) is applied to the resin, so the dynamic viscosity is low and it flows smoothly from the syringe. is discharged. However, once the resin is discharged from the syringe, it becomes static because it is released from the external force, and as a result, the viscosity of resin with high thixotropic properties increases, and the 1i11 resin injected into the through hole and its vicinity becomes After injection, the viscosity increases, loses fluidity, and hardens at the through hole, sealing the through hole liquid-tightly without flowing out to the bottom side of the circuit board.

If a resin with a low thixotropic strength is used as the filling resin, the viscosity of this filling resin must be significantly increased to prevent it from dripping from the through hole after injection. However, injecting a predetermined amount of such resin into a predetermined position using a syringe requires extremely high discharge pressure, making it impractical.

Further, the thixotropic property of J14 resin is specifically observed as a phenomenon in which when measuring the viscosity of the resin with a viscometer, the higher the rotational speed of the rotor of the viscometer, the lower the viscosity is measured. Normally, in order to quantitatively express this thixotropic property, the viscosity at the rotation speed of 10@ is measured, where the rotation speed of the viscometer is A rpm, and the viscosity at the rotation speed of 10 Arom is calculated, and the thixotropic index = viscosity at A rpa /10 Arpl.

As for the thixotropic property required for the filled resin in this example, the diameter of the through hole of the hybrid IC is approximately 0.3 to 0.88 in most cases, but the larger the diameter of the through hole, the more J+1te
It is necessary to increase the thixotropic property in order to prevent the outflow of fat. On the other hand, even if the resin has the same thixotropic property, if the viscosity is high, it is possible for the filled resin to pass through the through hole. However, even if only the viscosity is increased, the fluidity decreases, resulting in a significant decrease in workability.

Further, as the filling e+ fat, thermosetting materials such as epoxy, urethane, and silicone [f] are generally used. Therefore, since it is cured by heating, the viscosity of the filled resin decreases at high temperatures compared to the viscosity of the filled resin at room temperature, so it is necessary to select a filled resin so that it does not soften under the curing temperature conditions of heating and pass through the through holes. be.

EXAMPLE Hereinafter, an example in which the method of the present invention is implemented as a resin sealing method for a double-sided mounting type hybrid IC will be described with reference to FIG.

[Example 1] A hybrid IC 11 has a resin-sealable semiconductor element 13 and a chip component 14 mounted on one surface (the upper surface in FIG. 1) of an aluminum substrate 12 with a thickness of 0.8 am, and the other surface. A pressure sensor 15 is mounted on the surface (lower surface in FIG. 1), whose function may be impaired if the resin is applied.The pressure sensor 15 is formed on the alumina substrate 12 and has a diameter of 0. 5111#I through hole 12a
It is electrically connected to a circuit (not shown) formed on the opposite side via the. And these semiconductor elements 13
The alumina substrate 12, on which a chip component 14 and a pressure sensor 15 are mounted on each side, is housed in a case 16 made of PAT (polybutylene terephthalate) resin containing 30% glass fiber. 16
A ridge formed on the inner periphery of.

The alumina substrate 16a is placed on top of the case 16a, and its periphery is tightly sealed with a silicone adhesive 17 to horizontally fix the space inside the case 16 into two vertically. The lower end of the pressure sensor 15 mounted on the lower surface side of the pressure sensor 12 is arranged so as to face the outside of the case 16 through an opening 16c formed in the bottom 16b of the case 16.

Next, a case will be described in which the hybrid IC 11 housed in the case 16 as described above is sealed with resin.

The filled resin is A with high viscosity and high thixotropic properties.
4IA resin 18 has a viscosity of 200 voices and a thixotropic index of 5.0. 2F & thermosetting addition reaction type silicone botting resin, and B resin 19 has a low viscosity and low thixotropic property and has a viscosity of 5 voices. and a two-component thermosetting addition reaction type silicone botting resin with a thixotropink index of 1.0.

First, a highly thixotropic A
, 1i) When the I fat 18 is injected into the through hole 12a of the alumina substrate 12 and its vicinity, the A41) J fat 18 discharged from the syringe is released from external force and becomes static, increasing its viscosity. It loses fluidity and closes the through hole 12a liquid-tightly.

After that, B resin 19 with low viscosity and low thixotropic property is injected into the side of the alumina substrate 12 in the case 16 on which the semiconductor elements 13 and chip components 14 are mounted, and then heated at 120°C for about 1 hour. Then, the filled resin A 18 and resin B 19 are completely cured.

The finished product obtained in this way is inserted into the through hole 12a.
When the section was cut and the cross section was observed, it was found that the A@ fat 18 with high thixotropic properties was found in the through hole 12a.
The A resin 18 and the 8 resin 19 did not leak to the opposite side of the hybrid IC 11 through the 111, and the A resin 18 and the 8 resin 19 were not separated from each other from the interface between the resins 11 and 11.

[Embodiment 2] Embodiment 2 has the same structure as the same parts as Embodiment 1, so drawings are omitted and the same parts as Embodiment 1 are given the same symbol @ for explanation.

The hybrid IC 11 has a tree Iff on one side (top surface in FIG. 1) of an aluminum substrate 12 with a thickness of 0.635u.
A pressure sensor 15 is mounted with a sealable semiconductor element 13 and a chip component 14, and the other surface (lower surface in FIG. 1) has a pressure sensor 15 whose function may be impaired if IfA grease is applied.
is mounted, and this pressure sensor 15 is installed in a through hole 12 with a diameter of 0.45a formed in the aluminum substrate 12.
It is electrically connected to a circuit (not shown) formed on the opposite surface via a. And these semiconductor elements 1
3, chip parts 14, and pressure sensors 15 are mounted on each side of the aluminum substrate 12, which is made of alloy grade (alloy grade), which is a mixture of PET (polyethylene terephthalate) resin in PC (polycarbonate) 41 resin.
It is housed in a case 16 made of PCS resin, placed on a protrusion 16a formed on the inner periphery of the case 16, and its peripheral edge is liquid-tightly bonded with a silicone adhesive 17. It is fixed horizontally so as to divide the space inside the case 16 into two vertically. Also, this alumina substrate 1
The lower end of the pressure sensor 15 mounted on the lower surface side of the case 16 is arranged so as to face the outside of the case 16 through an opening 16c formed in the bottom 16b of the case 16.

Next, a case will be described in which the hybrid 1011 housed in the case 16 as described above is sealed with resin.

The filled resin is A with high viscosity and high thixotropic properties.
Resin 18 is a two-component thermosetting epoxy potting resin with a viscosity of 350 voices and a thixotropic index of 3.5, and B resin 19, which has a low viscosity and low thixotropic property, has a viscosity of 4.5 voices. and a two-component heat-curable addition-reactive silicone botting resin with a thixotropic index of 1.2.

First, when A tree rH18 with high thixotropic properties is injected into the through hole 12a of the alumina substrate 12 and its vicinity using a syringe, the A tree ejected from the syringe
Since the resin 18 is released from the external force, it becomes static, its viscosity increases, and it loses its fluidity to form the through hole 12a.
@'a Tightly occluded.

After that, B4111Jlif19, which has low viscosity and low thixotropic properties, was injected onto the side of the alumina substrate 12 in the case 16 on which the semiconductor elements 13 and chip components 14 were mounted, and then heated at 120°C for about 1W! The A41 fat 18 and the B464 fat 19 filled are heated for a period of f to completely harden.

The finished product obtained in this way is inserted into the through hole 12a.
When the cross section was observed after cutting at the section , it was found that the A resin 18 with high thixotropic properties was found in the through hole 12a.
The resin did not flow out to the opposite side of the hybrid IC 11 via the 1111i18.19, and the A-tree rfi18 and the 8-resin 19 adhered to each other and did not separate from the interface between the two resins 1111i18.19.

In both of the above embodiments, the 4M resin injected into the through holes 12a of the substrate 12 was a highly thixotropic resin. IfAffi for electronic industry uses Si 02 (
Alted silicon/silica) is used. In this way, when a large amount of 5i02 is added compared to normal resin, the coefficient of thermal expansion is lower and the thermal conductivity is higher than that before addition, but this is because a large amount of 5i02 is added. The properties of the resin obtained by this process are closer to those of the alumina substrate 12 on which the through holes 12a are formed, such as the coefficient of thermal expansion and thermal conductivity, thereby improving the durability and reliability of the through holes 12a, thereby improving the electronic component module. The reliability of the system can be further improved.

As described in detail, the method for resin-sealing an electronic component module of the present invention is to seal an electronic component module such as a hybrid IC, which has electronic components mounted on both sides of a substrate with through holes, into two chambers in a case. When filling the case with resin, the through holes of the board are closed using resin with high thixotropic properties, and then one of the cases divided by the board is filled with thixotropic resin. Since the resin is filled with a resin having low properties and sealed with the resin, leakage of the filled resin from the through hole can be reliably prevented, and electronic components such as sensors can be protected from damage caused by resin batter.

In addition, the through hole is #4I with high thixotropic properties.
ff, it is now possible to select a resin with optimal viscosity etc. as the filler resin for resin sealing, which eliminates the generation of air bubbles behind electronic components, resulting in highly reliable electronic components. It can be a module.

Furthermore, in this IIIAlrf sealing method for electronic component modules, conventional manufacturing equipment and manufacturing methods can be applied as they are in the filling process with filling resin, so there is no need to develop new manufacturing equipment or new manufacturing technology. , it is possible to manufacture highly reliable electronic component modules at low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an electronic component module using the method of the present invention, and FIGS. 2 and 3 are sectional views of electronic component modules using the conventional resin 14 fixing method. DESCRIPTION OF SYMBOLS 11... Hybrid IC, 12... Aluminum substrate, 12a... Through hole, 13... Semiconductor element, 14... Chip component, 15... Pressure sensor, 16... Case, 16b ...Bottom, 16c・
...Opening, 18... A resin with high thixotropic property, 19... 841411° with low thixotropic property Fig. 1 Fig. 2

Claims (1)

[Claims] An electronic component module such as a hybrid IC, which has electronic components mounted on both the front and back sides of a substrate with through holes penetrating the front and back sides, is housed in a case, and the case is filled with resin and the electronic component module is resin-sealed. In a resin sealing method for an electronic component module, the electronic component module is housed in a case so that the inside of the case is divided into two by the board, and the through holes of the board are first closed using a highly thixotropic resin. , a resin sealing method for an electronic component module characterized by filling only one side of a case divided by a substrate with a resin having low thixotropic property.