SU757608A1 - Method of producing anodized articles - Google Patents

Description

The invention relates to microelectronics, and more specifically to the technology of manufacturing aluminum anodized chip substrates. five

In modern electronics, in the manufacture of privately used schemes, aluminum anodized substrates are used, possessing a tremendous heat dissipation capacity and good | Electrophysical parameters.

A known method of manufacturing aluminum substrates for printed circuits, which consists in the fact that the workpiece in the form of a plate of aluminum or its alloy is polished, cleaned and electrochemically anodized to the thickness of the anodic oxide layer 0.5 μm [1]. This method does not allow an anodic oxide layer with high mechanical and insulating properties to be obtained on the aluminum substrate, since with an increase in the layer thickness to several microns, the anodic layer easily cracks under insignificant mechanical and thermal loads, and at thicknesses up to 1 μm, the electrical resistance is too low.

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The drawbacks of this process are partially eliminated in the method of manufacturing aluminum substrates of printed circuits based on applying polymer insulating layers to the anodized substrate, which increases the total electrical resistance of the insulating layers and eliminates the negative effects associated with cracking of the anodic oxide layer (2 ^. However, this method complicates production of substrates and dramatically reduces the thermal diffusing capacity of substrates, since the thermal conductivity of polymers is many times less than the thermal conductivity of oxide aluminum, a. more aluminum.

Also known is a method of manufacturing anodized products based on electrochemical anodizing of blanks, in which, to reduce the tendency of the anodic layer to rastratcracking, the anodized product is slowly heated to 93 ° C for 30 minutes and slowly cooled with the furnace [3]. Such heat treatment somewhat streamlines the structure, improves the uniformity of the anodic oxide layer, to some extent relieves mechanical stresses, as a result

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what anodized parts can

subsequently reheat to

200 ° C without significant damage

surface.

However, the known method does not provide an increase in the heat resistance of the anode layer of 250-300 ° C, i.e. to Temperatures that affect the substrate in the process of manufacturing circuits. The effect of increasing heat resistance is only given when the thickness of the anode layer is up to 5 microns and disappears completely at thicknesses of 40-60 microns.

The aim of the invention is to improve the quality of products by improving the heat resistance of the anodic oxide layer. This goal is achieved by the fact that in the method of manufacturing anodized products, mainly substrates, microcircuits, including electrochemical anodizing of a billet of aluminum or its alloy followed by heat treatment, heat treatment is carried out by heating the billet to a temperature above 400 ° C at a speed of at least 80 ° S / min

This method is based on the following physico-chemical patterns.

The aluminum oxide film formed by electrochemical anodizing has a porosity of up to 20%, the number of pores on the Heme ¹ surface is ΙΟ ⁸ -ΙΟ ³ , the pore diameter is 200-300 A is impossible. When heated in the anode film, aluminum oxide is hydrated by the reaction ΑΙ ^ Οτ, + H ^ O = 2A1O (OH) and the simultaneous evaporation of chemically unbound water. The resulting AT'hydration bozmit ATO (OH) gives the anode film a small. Plasticity, high fragility. Due to this, 'and also because of the huge difference in the thermal expansion coefficients of aluminum and aluminum oxide (22.4 * 10 " ⁶ and 6.4x10" *

1 / ° C, respectively) the anode film cracks easily. As the temperature rises further, the boehmite dehydrates, the film becomes less fragile and more plastic.

In all known methods of manufacturing anodized products, which include heat treatment after anodization, heating is carried out so that the formation of bozmite and evaporation of water occur in parallel, which is inevitably accompanied by cracking of the anode layer.

In the proposed method, a high heating rate allows the temperature range of intense hydration to be passed so quickly that no significant amounts of bozsmit are formed. At temperatures above 400 ° C, the hydration reaction is almost shifted to the left, therefore the formation of boehmite is impossible even in a humid atmosphere. In addition, heating above 400 ° C promotes the crystallization of amorphous alumina, which also increases the ductility of the oxide and. reduces the risk of cracking. The duration of heating set * based on the desired degree of crystallization of aluminum oxide and various technological requirements,

A total of 140 anodized aluminum substrates were thermally processed after anodization under various process conditions.

The substrate was made as follows. Sheet blanks of aluminum alloy AMgZ, size 78x95xx0.8 mm, were mechanically polished to grade 13 as per GOST 12592-67, cleaned from polishing pastes with organic solvents, annealed at 350 ° C for 1 h, anodized in oxalate acid electrolyte at a current density of 2 A / dm ² , temperature 2022 ° С for 2 h and washed in deionized water. The thickness of the oxide layer was 50-60 microns. Substrates · divided into 7 batches of 20 pcs. in batches.

Example 1. Patria 'No. 1 thermally treated by the proposed method, namely, heated to 4U ^b With a speed of 80 ° C / min For this purpose, the substrates in a metal cassette, ensuring the vertical position of the substrates and the separation of each substrate from the adjacent air gap, were placed in a pre-heated muffle furnace to 425 ° C. The heating rate of the substrates, up to 410 ° C, was 80 ° C / min, the Substrates were kept at 4 ° C for 40 minutes, after which they cooled with the furnace to 150 ° C and were taken out into the air.

Example 2. Party "2 processed by the method of the prototype. For this, the substrates were heated to 9–3 ° C, kept at this temperature for 30 min, and cooled with the oven to room temperature.

Note 3, _ Party No. 3 was heated at a rate of 10 ^ C / min to 410 ° C, kept in the furnace for 40 minutes, cooled with a furnace to 150 ° C and removed, into the air.

Example 4. Batch 4 was heated at a rate of 80 ° C / min to 350 ° C, kept in an oven at 350 ° C for 40 min, cooled with a furnace to 150 ° C and taken out into the air.

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Example 5. The party "5 was subjected to drying at 80 ° C for 30 hours.

Example 6, Party "6 not subjected to heat treatment.

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Example 7. Batch No. 7 was heated to 250 ° C at a rate of 10 ° s / min,

kept at 250 ° C for 40 minutes, cooled to 150 ° C with a stove and taken out on

air.

All substrates viewed under 5

microscope for the presence of cracks in the anodic oxide layer. The cracked substrates were rejected and removed from further tests.

Further, all the substrates with non-cracked anodic layer were tested for heat resistance under conditions simulating the tinning of the microcircuit substrates. To do this, the substrate was moistened with a flux containing 98 wt. % glycerol and 2% hydrochloric acid, immersed in solder PIC 40, heated to 250 ° C, kept for 1 min, cooled in air, washed in water and examined under the microscope for the presence of cracks, ·

All substrates made by the proposed method successfully passed the test.

A decrease in the heating temperature below 400 ° C while maintaining a high heating rate (batch No. 4) or a decrease in the heating rate while maintaining a high heating temperature leads to cracking of the anode layer of the substrate.

Anodized substrates, manufactured by the prototype method, as well as substrates thermally treated at 80 ° C at 250 ° C and thermally untreated substrates also do not have heat resistance. 35

Thus, the proposed method allows to increase the heat resistance

anodized substrates, which eliminates the cracking of the anode layer of the substrates during subsequent technological operations for manufacturing microcircuits associated with thermal effects, and even in conditions of tinning by dipping in solder, characterized by the most severe temperature conditions. This, in turn, reduces the number of ruptures of the film elements of the microcircuits, increases the yield of suitable microcircuits and reduces their cost.

Claims (1)

Claim A method of manufacturing anodized products, mainly substrates of microcircuits, including the electrochemical anodizing of a billet of aluminum or its alloy, followed by heat treatment, u and th with i am that quality of products by increasing the heat resistance of the anodic oxide layer, heat treatment is carried out by heating the workpiece to a temperature above 400 ° C at a speed of at least 80 ° C / min. about tl and h and us aim higher