JPH0772528B2 - Igniter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an AlN sintered body suitable for use as a heat sink of an automobile igniter, and more specifically, to a circuit-formed Si
The present invention relates to an igniter using an AlN sintered body for an igniter, which has a characteristic that a chip can be directly mounted on itself.

(Prior Art) An automobile igniter is made of, for example, an electrically insulating Al ₂ O ₃ substrate bonded with an adhesive resin in an Al case, and made of Cu, Mo, etc., which have excellent thermal conductivity. A metal layer having a predetermined thickness was joined, and a predetermined circuit was formed on the metal layer.
It is configured with a Si chip.

Here, the intermediate metal layer has a function of radiating the amount of heat generated in the Si chip.

(Problems to be Solved by the Invention) In the case of such an igniter having a conventional structure, the Al ₂ O ₃ substrate has a low thermal conductivity and thus has a poor heat radiation performance of the amount of heat generated from the Si chip. Therefore, it is necessary to interpose the metal layer as described above between the Al ₂ O ₃ substrate and the Si chip in order to improve the heat dissipation of the whole. However,
The coefficient of thermal expansion of Si is about 3.5 × 10 ^-6 / K, and that of Cu is about 17 × 10 ^{-6.
Since −6} / K and Mo are about 5.5 × 10 ⁻⁶ / K, when the Si chip generates heat, thermal stress is generated between these metal layers and the Si chip sometimes peels off.

Also, speaking from the standpoint of manufacturing, since the first Si chip mounting of joining metal layer on the Al ₂ O ₃ substrate is possible, in the igniter of the conventional structure, the the Al ₂ O ₃ substrate and the metal layer It is a premise to combine and with a combination of electrical insulation and heat dissipation. If the substrate is made of a material that has both of these characteristics and has a thermal expansion coefficient similar to that of Si, then no metal layer is required to be bonded and the Si layer is directly bonded onto this substrate.
It becomes possible to mount a chip.

Under such circumstances, the present inventors have begun to study an igniter using AlN as a substrate instead of the Al ₂ O ₃ substrate. This is because AlN has an electrical insulating property and at the same time has a large thermal conductivity and a high heat dissipation property, and its thermal expansion coefficient is 4 × 10 ^-6.
It is ~ 5 × 10 ^-6 / K, which is relatively close to that of Si.

By the way, when an AlN sintered plate is incorporated as a heat radiating plate for an igniter, design criteria regarding the shape, such as the width and thickness of the heat radiating plate, are largely defined by the characteristics listed above the AlN used.

However, to date, no report has been made on proper AlN characteristics when using AlN as a heat sink for an igniter.

An object of the present invention is to provide an igniter using an AlN sintered body that has appropriate characteristics as a heat sink of an igniter and can directly mount a Si chip on itself.

[Structure of the Invention] (Means for Solving Problems) The present inventors have made various studies on the characteristics required for the ceramic sintered plate when the Si chip is directly mounted on the ceramic substrate. The present inventors have found the fact that an AlN sintered plate having the characteristics described below is suitable and have developed the present invention.

That is, the AlN sintered body of the present invention has a product of heat capacity (C: J / K) and thermal conductivity (K: W / m · K) of 1.5 J ² / s · m · K ² · K or more. And has a coefficient of thermal expansion (α) of 1.5 × 10 ^{-6 /} K to 5.5 ×
It is characterized by being 10 ⁻⁶ / K.

Of these characteristics, the value of C × K is a parameter that defines the heat dissipation property of the AlN substrate when incorporated as an igniter substrate. This value is 1.5J ² / s ・ m ・ K ²
・ If it is smaller than K, the amount of heat generated in the Si chip is not quickly dissipated and accumulates, and as a result, accidents such as circuit breakage begin to occur frequently.

Also, as the igniter, the larger the electric resistivity (ρ), the more effective it is in terms of electrical insulation, but as a heat sink of the igniter, it is 0.5 × 10 ¹⁴ Ωcm or more, preferably 1 × 10 ¹⁴ Ω ・It should be at least cm.

α is preferably that approximates α value of Si as much as possible is set to ^{1.5 × 10 -6 /K~5.5×10 -6 / K} . α is 1.5
Ceramics smaller than × 10 ^-6 / K are virtually impossible to manufacture industrially, and ceramics larger than 5.5 × 10 ^-6 / K have too large an α difference from the mounted Si chip. Delamination phenomenon due to thermal stress occurs.

The AlN sintered body having any of these characteristics can be manufactured by a commonly used method.

However, at that time, type and purity of raw material powder, particle size; type, purity, particle size of sintering aid; mixing ratio of sintering aid; molding method of green compact, molding conditions (pressure, temperature, etc.) It is necessary to appropriately change and combine the respective conditions in the manufacturing process such as; sintering conditions such as temperature, time and atmosphere during sintering.

For example, ₃ to 5 wt% of Y ₂ O ₃ powder of 1.0 μm or less is added to AlN powder having an average particle size of 1.5 μm and O ₂ impurities of 2 wt% or less, and they are mixed sufficiently. Then, a binder is added to make a slurry, and a doctor blade is used to form a sheet. After degreasing, it is preferable to set each condition such that firing is performed at 1800 ° C. for 2 hours in a N ₂ atmosphere.

By applying such an AlN sintered body as a substrate having excellent heat dissipation, it is possible to provide an igniter directly mounted with a Si chip.

(Examples of the invention) Example 1 97 parts by weight of AlN powder having an oxygen content of 1 to 2% by weight and an average particle size of 1.5 μm and 3 parts by weight of Y ₂ O ₃ powder having a purity of 99.99% and an average particle size of 0.8 μm. It was put in a ball mill and thoroughly mixed and crushed.

Acrylic resin was added as a binder to the resulting mixed powder.
After adding and mixing parts by weight, the resulting particles are sized to an average particle size of 50 μm, and the resulting granules are filled in a mold to obtain 1000 kg at room temperature.
Molded at a pressure of / cm ² .

The resulting molded body is degreased at 700 ° C to remove the binder by thermal decomposition, then put in a nitrogen atmosphere furnace and heated at a temperature rising rate of 150 ° C / hr up to 1800 ° C for 2 hours at 1800 ° C. After holding and sintering, the temperature was lowered at 300 ° C./hr and cooled.

Each characteristic of the obtained sintered body was measured and shown in the table. Also, from this sintered body, 50 boards with a length of 14 mm, a width of 10 mm, and a thickness of 0.635 to 3.0 mm are cut out, and these boards are used as heat sinks by directly soldering Si chips onto them and incorporating them by an ordinary method to form an igniter. I made it.

Set the power transistor in these igniters to V _CB = 30
V, is operated under the condition of I _E = 1.5A, to measure the temperature rise on the Si chip _{(mV) (I M = 20mA} , S D = 100μs). The results are shown in the table.

Example 2, Comparative Examples 1 to 7 For comparison, a Si ₃ N ₄ and Al ₂ O ₃ substrate having the same shape as that of Example 1 was prepared, and a Si chip was mounted on each of them through a Mo layer having a thickness of 1.5 mm. I made a structural igniter. The measurement results during the operation are also shown in the table.

The AlN sintered bodies with various characteristics were manufactured by changing the manufacturing conditions variously. Using these sintered bodies, an igniter was assembled in the same manner as in Example 1 and its performance was measured. The results are tabulated together.

[Effects of the Invention] As is clear from the above description, all of the AlN substrates satisfying all of the above characteristics have good heat dissipation and are suitable as a heat sink for an igniter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideki Sato Inventor Hideki Sato 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Inside the Yokohama Yokohama metal factory (56) Reference JP-A-56-66086 (JP, A) JP 53-102310 (JP, A) JP-A-60-178688 (JP, A)

Claims (1)

[Claims] 1. The product of heat capacity and thermal conductivity is 1.5 J ² / s · m · K.
^It has a value of ² or more and a thermal expansion coefficient of 1.5 × 10 ^{-6 /} K ~ 5.5
An igniter characterized by directly mounting a Si chip on an AlN substrate of × 10 ^-6 / K.