These steps are adjusted in various ways to achieve desired results for the various processing applications. Typical process profiles share a common sequence: Chamber Preparation, Vacuum Pre-Bake, Final Seal and Cool Down. It is recommended to open the process chamber when the temperature is below 200C to prevent graphite from reacting with oxygen in the air. For most glasses, the components are cooled un-assisted until 20C below the softening point.Īssisted cooling is performed by continuously flowing inert gas into the chamber, with the exhaust valve open. For most solders and braze materials, the components are cooled un-assisted until 10C below the flow point. The Cool Down is the final phase of the process cycle. For most glasses, the optimum dwell is about 1-1/2 minutes. For most solders and braze materials, the optimum dwell is about 2 minutes. For most glasses, the optimum process temperature is about 80C above the softening point. For most applications, a brief dwell at high temperature is preferred over a long dwell at low temperature.įor most solders and braze materials, the optimum process temperature is about 50C above the flow point. The relationship of temperature and time becomes important when heat-sensitive components are involved. By lengthening the dwell time, the temperature can be lowered. By raising the temperature, the dwell time can be shortened. The time and temperature parameters are intimately related. This procedure relieves the internal stresses within the tin deposit that can be responsible for whisker growth. After being plated with tin, continuous coil-stock or stamped parts are run through a reflow chamber where the tin is heated to its melting point and then cooled. The Final Seal dwell is the interval when the temperature is maintained at its highest level. How the tin reflow plating process works. The pre-bake temperature is typically set to 50C below the reflow temperature of the bonding material. It improve the thermal gradient in preparation for the final seal.It removes contaminants trapped interstitially in the piece-parts.It removes contaminants adhering to the surfaces of the piece-parts.It removes contaminants present in the process chamber’s ambient atmosphere.This vacuum/pressure step can be repeated to further increase the cleanliness of the sealing environment and reduce the overall moisture level.Ī vacuum pre-bake provides the following benefits: Inert gas, usually dry nitrogen, is then introduced into the chamber. Vacuum is turned on until the chamber reaches a low pressure. Most process cycles begin by removing as much of the ambient atmosphere as possible and diluting what remains with an inert gas. These process profiles share a common sequence. 1) one-side mounting: pre-applied solder paste patch (divided into manual mounting and machine automatic mounting) reflow soldering inspection and electrical testing. Typical applications for the family of SST Vacuum Reflow Systems are: Package Assembly, Lid Attach, Die Attach, Glass to Metal Seals, and Brazing. Reflow welding process for the surface mount of the board, the process is relatively complex, can be divided into two: one side mount, two side mount.
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