JPS5950210B2 - electronic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum case resin-sealed electronic component with excellent moisture resistance.

As shown in the figure, the structure of an electronic component is well known, in which an element 2 is housed in a bottomed aluminum case 1, a resin 3 such as an epoxy resin is injected and filled through the open end, and the resin is heated and hardened to seal the element 2.

However, the moisture resistance of electronic components sealed in this manner is not necessarily satisfactory.

For example, if a capacitor configured as described above containing element 2 of an aluminum solid electrolytic capacitor whose characteristic values change sharply due to moisture absorption is subjected to a moisture resistance test at 40°C, 95%, for 500 hours, the capacitance will change. Something that changes greatly occurs. That is, the rate of change in capacitance in the moisture resistance test is 2%.
Approximately 10% of the cases exceed 10% (distributed between 2% and 5%). As a result of various researches to improve this, the inventor found that
It has been discovered that annealing the aluminum case before filling the case with resin brings about a decisive improvement effect.

Naturally, the annealing conditions will vary depending on the material of the metal case, and even for the same material, the appropriate time will vary depending on the annealing temperature.

First, an experiment on adhesion between aluminum and resin by aluminum annealing will be shown.

Aluminum plate 4 processed into an L shape as shown in Fig. 3
I prepared two. Each aluminum plate has the same shape,
Thickness: ■ 0.8 mm, width W: ■ 10-size mold, adhesive surface height: ■ 10-size mold. Two aluminum plates 4 whose adhesive surfaces 5 are finally polished with 2000 emery paper to give them a mirror surface.
, 4, (A) annealing at 550°C for 30 minutes or (
B) vacuum annealing at 550°C for 30 minutes at 10° to 100°C, or (C) no treatment at all, and then using aluminum pieces in each treatment state, As shown in Figure 4, the adhesive surfaces are placed opposite each other, and epoxy resin 6 is filled between the opposing surfaces. Next, the opposing adhesive surfaces are pressure-welded at 1 kg/cm2 to reduce the thickness of the resin 6 to 0.
．． 3 mm, and the resin was cured in that state. A destructive test was conducted on each of these samples to determine how much tensile force could be used to separate the paired aluminum pieces 4, 4 from each other.
The results are shown in the table below. From the above experimental results, the annealing effect of aluminum is remarkable. This effect also occurs when the aluminum surface is oxidized by oxygen in the air during annealing.
It becomes a film of aluminum pentoxide oxide, and the oxygen in this oxide film and
It was confirmed that this occurs due to strong bonding force called hydrogen bonding between the hydroxyl groups of the resin. Next, an example will be given regarding a capacitor in which an aluminum case is used and an aluminum solid electrolytic capacitor (rated at 0.1 μF/25V) is sealed with epoxy.

Example 1: Case purity 99.3%, case size φ3.5
x7 mm (wall thickness 0.1 mm), annealing temperature 550°C, annealing time 5 minutes Example 2: Case purity and dimensions are the same as Example 1.

Annealing temperature: 300°C, annealing time: 30 minutes Example 3: Case purity and dimensions are the same as Example 1.

Annealing temperature: 550°C, annealing time: 30 minutes Reference example 1: Case purity and dimensions are the same as in Example 1.

No pre-heat treatment such as annealing of the case. Reference Example 2: Case purity and dimensions are the same as in Example 1.

Vacuum annealing for 30 minutes at 550°C and 10-5T0rT The results of the moisture resistance test of each of the above Examples and Reference Examples are summarized in the table below.

(Test conditions were 40° C., 95% relative humidity, 500 hours) As seen in the test results above, none of the Examples had a capacitance change rate of more than 2%.

In the case of Reference Example 2, an improvement effect of about 1/5 of the occurrence rate of Reference Example 1 is observed, but this is because the case itself has become soft due to the heat treatment of the aluminum case, and therefore the curing shrinkage of the resin. This is because the case becomes appropriately distorted as the resin and the case become stuck together. In addition to this effect, the present example exhibits perfect moisture resistance due to the bonding force due to hydrogen bonds between the aluminum oxide film and the resin, as described above. As described above, according to the present invention, variations in moisture resistance can be suppressed with an extremely simple structure, and the incidence of defects can be significantly improved.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a typical aluminum case resin-sealed electronic component, Figure 2 is a plan view of the same, Figure 3 is a perspective view of an aluminum plate used for destructive testing, and Figure 4 shows the state of destructive testing. FIG. 1... Aluminum case, 2... Element, 3... Resin.

Claims (1)

[Claims] 1. An electronic component formed by filling and hardening a resin into an aluminum case housing an element, wherein the aluminum case is annealed in advance before being filled with the resin.