Wafer fixing surface paste method and SMT wafer fixing device

Abstract

The invention discloses a wafer fixing surface paste method to fix and attach a wafer on a substrate. The method comprises the steps that solder paste is printed in a primary solder paste printing area on the substrate to form a primary solder paste layer; the substrate is heated to volatilize a flux in the primary solder paste layer; the primary solder paste layer is cooled; the cooled primary solder paste layer is punched, so that the top of the primary solder paste layer is in a horizontal plane; solder paste is printed in a secondary solder paste printing area on the punched primary solder paste layer to form a secondary solder paste layer, wherein the area of the secondary solder paste layer is smaller than the area of the primary solder paste layer; the wafer is attached on the substrate through the secondary solder paste layer; and reflow soldering is carried out on the substrate on which the wafer is attached to fix and attach the wafer on the substrate. Compared with the prior art, the method provided by the invention has the advantages that a part of the solder paste which is not attached is heated to volatilize the flux, which effectively reduces the size and number of the bubbles generated by heating after sticking; and the method can be used for fixing and attaching a thin wafer. The invention further discloses an SMT printing steel mesh and an SMT wafer fixing device.

Description

technical field [0001] The invention relates to an SMT process, in particular to a device and a method for pasting and fixing a wafer on a substrate in the SMT process. Background technique [0002] The existing method of fixing the wafer with solder paste (Solder Die Attach) adopts the printing method of solder paste. After the solder paste is printed from the stencil to the substrate, the wafer / component is then pasted, and the solder paste is soldered through the reflow furnace. Wafers / components etc. are fixed on the substrate. [0003] However, due to the flux (rosin) contained in the solder paste material, since the volatilization of the flux is hindered after the wafer is attached, it will become air bubbles and remain at the bottom of the wafer during subsequent reflow soldering, forming solder voids. For thicker wafers, solder voids will not cause serious problems, but with the development of wafer technology, the thickness of wafers becomes thinner, and the risk o...

AI Technical Summary

Problems solved by technology

Especially due to the complex chip packaging process, after completing the thin wafer bonding / fixing process, gold wire welding (connecting the wafer and substrate), injection molding (black glue wrapping the wafer) and other processes are required, which will affect the thin wafer. Pressure is generated especially at the void position, causing the wafer to crack, resulting in product scrapping

[0004] Furthermore, before the existing wafer is pasted, the solder paste is printed. Due to the tension of the liquid, the upper surface of the printed solder paste layer tends to be curved. At this time, when the wafer is pasted on the solder paste layer , tends to make the wafer paste tilt due to the uneven top of the solder paste layer, making the supported product wafer more likely to break

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