Method for increasing balling rate of metal convex block in vacuum backflow technology

A technology of vacuum reflow and metal bumps, which is applied in the manufacture of electrical components, electrical solid devices, semiconductor/solid devices, etc., can solve the problem of low ball forming rate, and achieve the effect of improving roughness and improving low ball forming rate

CN104485293AActive Publication Date: 2015-04-01NANTONG FUJITSU MICROELECTRONICS
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Patent Information

Authority / Receiving Office
CN · China
Current Assignee / Owner
Publication Date
2015-04-01

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Abstract

The invention provides a method for increasing the balling rate of a metal convex block in a vacuum backflow technology in the field of semiconductor encapsulation. The method specifically comprises the following steps: (1) allowing a spherical or square metal welding flux convex block to form on a UBM (under bump metal); (2) cleaning the metal welding flux convex block prepared in the step (1) by a hairbrush; (3) putting the metal welding flux convex block treated in the step (2) into a vacuum backflow furnace for backflow; (4) cooling the metal convex block subjected to backflow in the step (3) to the temperature lower than 40 DEG C under a vacuum condition. According to the method disclosed by the invention, the problem of low balling rate of the metal convex block in the vacuum backflow technology can be solved, and the balling rate is increased from 99.5 to 99.98 percent; meanwhile, the surface roughness of a balled metal convex block is also effectively improved.
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Description

technical field

[0001] The invention relates to the field of semiconductor packaging, in particular to a method for improving the ball forming rate of metal bumps in a vacuum reflow process. Background technique

[0002] The production of tin-lead and tin-silver bumps is a necessary part of advanced semiconductor packaging (FC flip-chip packaging). In the process of semiconductor packaging, it is necessary to prepare bumps on the pad area of ​​the wafer first, then grind the back of the wafer to a certain thickness and cut it into individual chips, and connect the metal bumps on the chip to the metal pads on the substrate Bump bonding. Solder bump fabrication technology is a key technology in flip-chip, and the reliability of semiconductor devices largely depends on the structure and material of each solder bump, as well as the effectiveness of their electrical interconnection. Therefore, the consistency of the height and volume of each solder bump is critical.

[0003] A...

Examples

Embodiment 1

[0023] A method for improving the ball forming rate of metal lead bumps in a vacuum reflow process, comprising the following steps:

[0024] (1) Forming spherical or square metal solder bumps on UBM (Under Bump Metal);

[0025] (2) cleaning the metal solder bump prepared in step (1) through a brush;

[0026] (3) placing the metal solder bump processed in step (2) in a vacuum reflow furnace for reflow;

[0027] (4) The metal solder bump after reflow in step (3) is cooled to below 40° C. under vacuum condition.

[0028] Wherein, the metal solder bump in step (1) is a tin-lead bump, and the method for forming the tin-lead bump is an electroplating method, and its preparation method is to deposit the bottom metal layer of the bump on the wafer by sputtering, Then cover a layer of photoresist layer on the bottom metal layer of the bump, perform exposure and development to form the area of ​​the solder bump, then electroplate solder, remove the photoresist and etch.

[0029] In s...

Embodiment 2

[0038] A method for improving the ball forming rate of metal lead bumps in a vacuum reflow process is characterized in that it comprises the following steps:

[0039] (1) Forming spherical or square metal solder bumps on UBM (Under Bump Metal);

[0040] (2) cleaning the metal solder bump prepared in step (1) through a brush;

[0041] (3) placing the metal solder bump processed in step (2) in a vacuum reflow furnace for reflow;

[0042] (4) The metal solder bump after reflow in step (3) is cooled to below 40° C. under vacuum condition.

[0043] Wherein, the metal solder bump in step (1) is a tin-silver bump, and the method for forming the tin-silver bump is an electroplating method, and its preparation method is the same as that of the aforementioned embodiment 1.

[0044] In step (2), the cleaning time of the brush is 120 seconds, and the brush is a steel belt winding nylon brush roller with a particle size of 2000 mesh alumina contained in the needle.

[0045] In step (3),...

Embodiment 3

[0047]A method for improving the ball forming rate of metal lead bumps in a vacuum reflow process is characterized in that it comprises the following steps:

[0048] (1) Forming spherical or square metal solder bumps on UBM (Under Bump Metal);

[0049] (2) cleaning the metal solder bump prepared in step (1) through a brush;

[0050] (3) placing the metal solder bump processed in step (2) in a vacuum reflow furnace for reflow;

[0051] (4) The metal bump after reflow in step (3) is cooled to below 40° C. under vacuum condition.

[0052] Wherein, the metal solder bumps in step (1) are tin-lead or tin-silver bumps, and the method for forming the tin-lead or tin-silver bumps is the stud bump method.

[0053] In step (2), the cleaning time of the brush is 120 seconds, and the brush is a round-hole embedded nylon brush roller containing silicon carbide with a particle size of 1500 mesh in the needle.

[0054] In step (3), the reflow temperature of the vacuum reflow furnace is 180...