The Role of Industrial Ovens in Chip Packaging and Curing

In the process of chip packaging, Industrial ovens play a vital role in removing moisture, relieving stress, and curing packaging materials. Chips may absorb a certain amount of moisture before packaging. Industrial ovens can effectively remove this moisture through high-temperature heating, preventing oxidation inside the chip during subsequent processes and enhancing the stability and reliability of the chip. During packaging, different materials have different coefficients of thermal expansion, which can cause stress inside the chip when the temperature changes. The baking process of the oven can help packaging materials gradually adapt to temperature changes and release internal stress. The adhesives and epoxy resins used in packaging need to be cured quickly under the suitable temperature conditions provided by the oven to increase the mechanical strength and thermal stability of the packaging materials, ensuring that the chip is firmly fixed on the substrate in different operating environments and improving packaging quality.

I. The Role of Industrial Ovens in Chip Packaging and Curing

1.Moisture Removal: In the production of electronic components, moisture is a potential source of damage. Before packaging, the surface of the chip may absorb a certain amount of moisture. If not removed, this moisture can cause oxidation inside the chip during subsequent production or use, affecting the chip's performance and lifespan. Industrial ovens can effectively remove moisture from the chip's surface through high-temperature heating, ensuring that the chip is dry before packaging, thereby improving its stability and reliability.

2.Stress Relief: During chip packaging, different materials have varying coefficients of thermal expansion. When the temperature changes, stress can be generated inside the chip. If not relieved in time, this stress can lead to performance degradation or failure of the chip during use. The baking process of the industrial oven allows packaging materials to gradually adapt to temperature changes, thereby releasing internal stress and enhancing the stability and reliability of the chip.

3.Curing Packaging Materials: In chip packaging, various adhesives and epoxy resins are commonly used to fix the chip to the substrate or fill gaps between the chip and lead frame. Industrial ovens can provide the appropriate temperature conditions to accelerate the chemical reactions of these packaging materials, enabling them to cure quickly. This enhances the mechanical strength and thermal stability of the packaging materials, ensuring that the chip is firmly fixed on the substrate in different operating environments and improving packaging quality.

II. Baking Processes in Chip Packaging and Curing

1.Substrate Baking: During assembly, organic substrates used in PGA, BGA, and CSP packaging need to be baked to remove potential moisture. The baking temperature and time will vary depending on the substrate material and specific requirements, generally ranging from 125°C to 175°C for 1 to 6 hours.

2.Underfill Curing: For flip-chip (FC) dies, after being soldered to the substrate, the gap between the IC die surface and the substrate is filled with low-viscosity, silica-filled epoxy resin "underfill." After filling, the chip needs to be placed in an industrial oven for baking and curing to reduce the mismatch of thermal expansion coefficients between the die and the laminated substrate. The curing temperature is usually between 125°C and 150°C, with a duration of about 1 to 2 hours.

3.Heat Sink Curing: With increasing chip power consumption and decreasing die size, more and more packaging requires attaching heat sinks to the package and FC die backside. A variety of adhesive materials are used for this application, in liquid and film forms. After the heat sink is attached to the chip, it needs to be baked and cured in an industrial oven to ensure proper curing of the adhesive and good bonding between the heat sink and the chip, thereby improving heat dissipation. The curing temperature is generally between 150°C and 175°C, with the time depending on the type of adhesive and specific requirements, usually ranging from 1 to 3 hours.

4.Die Attach Curing: In most wire bonding (WB) applications, IC dies need to be attached to metal lead frames or laminated substrates. The adhesive contains filler particles to make it conductive or insulating, depending on whether the chip backside requires electrical bias or thermal connection. In multi-chip and stacked chip applications, the die bonding and curing operations may be repeated two to five times. After each bonding, the chip needs to be placed in an industrial oven for curing to ensure proper curing of the adhesive and reliable bonding. The curing temperature is generally between 150°C and 175°C, with a duration of about 1 to 2 hours.

5.Coating Curing: To protect IC chips from corrosion by ionic impurities in the mold compound, as well as to prevent line sweep and electrical short circuits on the mold, a coating process is used. After coating long, fine-pitch wire bonding, the chip needs to be placed in an industrial oven for baking and curing to fully cure the coating material and form a dense protective film. The curing temperature is usually between 125°C and 150°C, with a duration of about 30 minutes to 1 hour.

6.Encapsulation Curing: For COB applications with WB or FC interconnections, liquid, silica-filled epoxy resin materials are commonly used for encapsulation. After filling the blocked areas with low-viscosity, self-leveling epoxy resin, the chip needs to be placed in an industrial oven for curing to ensure good, void-free adhesion between the filling material, dam material, and underlying components. The curing temperature is generally between 125°C and 150°C, with a duration of about 2 to 4 hours.

7.Potting Curing: Liquid sealants are often used to package optical components, such as LED lights and displays, as well as many large electronic component housings. After potting is completed, the product needs to be placed in an industrial oven for baking and curing to ensure proper curing of the sealant and achieve good sealing effects. The curing temperature is usually between 100°C and 125°C, with the time depending on the type of sealant and specific requirements, generally ranging from 1 to 2 hours.

III. Types of Industrial Ovens Suitable for Chip Packaging and Curing

1.Hot Air Circulation Oven: The hot air circulation system ensures uniform temperature inside the oven, improving thermal efficiency. It is suitable for curing and baking various chip packaging materials and can meet the requirements for temperature uniformity in different processes. For example, in the underfill curing process of chips, a hot air circulation oven can ensure uniform temperature across the entire chip area, enabling uniform curing of the filling material and ensuring the consistency of curing quality.

2.Vacuum Oven: It can bake in a vacuum environment, effectively removing air and moisture from the materials. In some special processes of chip packaging, such as baking and curing of packaging materials that are prone to oxidation or highly sensitive to moisture, a vacuum oven can prevent material oxidation and moisture retention, thereby improving the reliability and stability of the packaging. For example, in the packaging process of some high-end chips, a vacuum oven is used for heat sink bonding and curing to avoid the influence of oxygen on the adhesive during the curing process and ensure the reliability of the bonding effect.

3.Infrared Tunnel oven:Utilizing infrared radiation for heating, it has the advantage of fast heating speed. It is suitable for chip packaging and curing processes that require high heating speed. In a chip's fast packaging production line, an infrared tunnel oven can quickly bring the packaging material to the curing temperature in a short time, improving production efficiency. However, it should be noted that the infrared tunnel oven has certain requirements for the material's heat absorption and radiation characteristics. During use, adjustments should be made according to different materials to ensure the curing effect.

Industrial ovens play an irreplaceable role in the chip packaging and curing process, from removing moisture and relieving stress to curing packaging materials, ensuring the performance and reliability of chips. Different chip packaging and curing processes, such as substrate baking, underfill curing, and heat sink curing, all rely on the precise temperature control and stable environment provided by industrial ovens. Types of ovens such as hot air circulation ovens, vacuum ovens, and infrared tunnel ovens each have their own characteristics and can meet a variety of production needs.