Substrate and process for mounting chip on substrate

Abstract

The invention relates to a substrate and a process for mounting a chip on the substrate. The substrate comprises a substrate body and a chip mounted on the substrate body, wherein pads of a solder layer are arranged on the substrate body, and the chip has electrodes connected to the pads. The pads are configured to be larger than the electrodes. Therefore, after solder melts, even if drum-shaped solder joints appear, a firm bonding surface and firm bonding force can be provided, and the risk of solder joint failure is greatly reduced. In addition, because the area of the pads is increased, the area of the solder coating the pads is increased. Therefore, the design can increase the binding force between the solder and the pads and reduce the occurrence of reliability decline caused by interface deterioration. In addition, by appropriately choosing the sizes of the pads, possible chip tilt after an LED chip is mounted on a flexible substrate can be effectively avoided, the porosity is reduced, and the reliability of solder joints can be improved.

Description

technical field [0001] The invention relates to a substrate, in particular to a flexible substrate on which a chip, especially a light emitting diode (LED) is installed. The present invention also relates to a process for mounting chips on a substrate, especially a process for mounting LED chips on a flexible substrate. Background technique [0002] Chips need to be mounted on substrates in the production of various electronic devices. For example, with the increasing popularity of light emitting diodes (LEDs), it is often necessary to mount LED chips on flexible substrates. [0003] Traditionally, LED chips mounted on flexible substrates are roughly divided into two types, namely front-mounted LED chips and flip-chip LED chips. For front-mounted LED chips, it is hoped that the bonding process can be saved by using flip-chip welding, avoiding lead wire shading, and improving heat dissipation performance. However, since there is a certain height difference (for example, ab...

AI Technical Summary

Problems solved by technology

However, since the AuSn plating layer on the electrode of the LED chip has a thickness of only about 5 μm, the requirements for the surface flatness of the substrate pad are relatively high.

Otherwise, it is easy to produce the problem of solder joint holes, especially for flexible substrates, which is very unfavorable

At the same time, the AuSn reflow soldering process requires a temperature of 300-320°C, which is too high for a flexible substrate, and may easily lead to problems such as pad warping and yellowing of the reflective layer of the substrate.

However, if BGA reflow soldering is also used, the above-mentioned problems of solder joint failure and chip inclination for the formal LED chip still exist.

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