Solder paste laser induced forward transfer device and method

Patent metadata

Field	Value
Publication number	US-11554435-B2
Application number	US-202016733751-A
Country	US
Kind code	B2
Filing date	Jan 3, 2020
Priority date	Jan 4, 2019
Publication date	Jan 17, 2023
Grant date	Jan 17, 2023

Abstract

The present invention discloses a solder paste laser induced forward transfer device and method. The device comprises a laser, a beam shaping module, an optical path adjustment module, a solder paste transfer module and a computer control system, wherein the laser is connected to the beam shaping module, followed by the optical path adjustment module, and the solder paste transfer module is located below the optical path adjustment module. The beam shaping module comprises a beam expanding lens, an aperture, a flat-top beam shaper and a spatial light modulator. The optical path adjustment module comprises a two-dimensional galvanometer and an f-θ lens. The solder paste transfer module consists of a transparent substrate, a solder paste film, a clamp, a Z-axis lifting table, a receiving substrate, and an XYZ precise moving platform. The computer control system consists of a computer and drivers of other devices. The device and method can achieve mask-free, non-contact and high-precision solder paste transfer, thereby greatly shortening the production cycle and reducing the production cost.

First claim

The invention claimed is:

1. A solder paste laser induced forward transfer device, comprising:
a laser unit,
a computer control system; and
a solder paste transfer module,
wherein the computer control system controls laser beam emitted from the laser unit and motion of the solder paste transfer module;
the solder paste transfer module comprises a transparent substrate, a clamp, a Z-axis lifting table, a receiving substrate, and an XYZ-axis moving platform;
a lower surface of the transparent substrate has a groove for receiving a solder paste film;
the receiving substrate and the Z-axis lifting table are placed on the XYZ-axis moving platform to adjust relative positions of the receiving substrate and laser beam spots;
the clamp is mounted on the Z-axis lifting table; and the groove of the transparent substrate faces downward and is placed in parallel above the receiving substrate, and the clamp clamps an edge of the transparent substrate and is carried by the Z-axis lifting table to vertically lift above the receiving substrate so as to adjust a distance between the transparent substrate and the receiving substrate.

2. The solder paste laser induced forward transfer device according to claim 1 , wherein the laser unit comprises a laser emitter, a beam shaping module, and an optical path adjustment module that are sequentially connected by an optical path; and
the laser emitter, the beam shaping module, the optical path adjustment module, and the solder paste transfer module are respectively connected to the computer control system.

3. The solder paste laser induced forward transfer device according to claim 2 , wherein the beam shaping module comprises beam expanding lens, an aperture, a flat-top beam shaper, and a spatial light modulator that are sequentially connected by the optical path; and
the optical path adjustment module comprises a two-dimensional galvanometer and f-θ lens that are sequentially connected by an optical path.

4. The solder paste laser induced forward transfer device according to claim 3 , wherein the groove for receiving the solder paste film has a depth of 20-150 μm.

5. The solder paste laser induced forward transfer device according to claim 4 , wherein the receiving substrate is a PCB.

6. A solder paste laser induced forward transfer method, wherein the method is implemented by using the solder paste laser induced forward transfer device according to claim 5 , comprising the following steps:
step (1): importing a circuit diagram of the receiving substrate to be printed into the computer control system, planning, by the computer control system, a scanning route and scanning speed of a laser beam according to positions of pads on the receiving substrate to be printed, and selecting laser parameters and parameters of the beam shaping module according to shape and size of each pad;
step (2): selecting the transparent substrate having a desired groove depth according to a thickness of a solder paste required in actual production, and coating the solder paste into the entire groove by blade coating to form the solder paste film in the groove; keeping the solder paste film facing downward, then fixing the transparent substrate by the clamp to which the Z-axis lifting table is connected; and adjusting the distance between the transparent substrate and the receiving substrate;
step (3): before each laser pulse emission, controlling, by the computer control system a rotation of a two-dimensional galvanometer according to a pre-planned route to change the laser beam path;
step (4): causing the beam emitted by the laser emitter and shaped by the beam shaping module to enter the optical path adjustment module composed of the two-dimensional galvanometer and f-θ lens; after a direction of the optical path is changed by the two-dimensional galvanometer, finally focusing the beam, after the beam passing through the f-θ lens, above the solder paste film of step; wherein after the laser beam passes through the transparent substrate and is absorbed by the solder paste film, an irradiated portion is partially vaporized, bubbles are formed inside the solder paste film, surrounding unvaporized portion is impelled toward the receiving substrate with continuous expansion of the bubbles, and a stable bridge structure is formed between the transparent substrate and the receiving substrate; and
step (5): repeating step and step until the stable bridge structures are formed between all the pads on the receiving substrate and the transparent substrate; thereafter, controlling, by the computer control system, the Z-axis lifting table to rise, so that the transparent substrate vertically leaves the receiving substrate, all the bridge structures break to leave solder paste voxels, and an entire of the receiving substrate is thus printed.

Assignees

• Univ South China Tech

Inventors

• Zhang Xianmin
• Shan Yilin
• Li Kai
• Tang Chuangang

Classifications

• G05B15/02

  electric · CPC title

• B23K26/0622

  by shaping pulses · CPC title

• B23K1/0056 Primary

  soldering by means of beams, e.g. lasers, electron beams [EB] · CPC title

• B23K26/34

  Laser welding for purposes other than joining · CPC title

• B23K3/0638

  for viscous material feeding, e.g. solder paste feeding (B23K3/0623 takes precedence) · CPC title