CN104006999B - Supporting fixture of drop test PCB - Google Patents

Abstract

Belonging to the material test field, the invention relates to a drop test PCB and a supporting fixture thereof. The drop test PCB comprises a cube-shaped PCB (1). Daisy chains (2) are arranged at the middle position of each edge of the square. The lead wire diameter (4) of the daisy chains (2) and the solder ball diameter dimension are approximately identical. Starting and ending solder pads of the lead wires (4) of the daisy chains (2) are located at the middle positions of the PCB (1). Four corners of the PCB (1) are equipped with holes (5) for fixing the PCB (1) on a drop table. The supporting fixture is simple to operate, and can reduce working intensity and ensure test repeatability and stability.

Description

A matching jig for drop testing PCB boards

technical field

The invention relates to a design of a PCB board for board-level drop testing, and a supporting jig for fixing a PCB board in the process of grinding and polishing sample preparation and microstructure observation, belongs to the field of material testing, and is suitable for observing the board-level drop testing process The process of initiation, expansion and disconnection of solder joints is applied to the reliability research of drop test in electronic packaging.

Background technique

For now, the replacement speed of electronic products has far exceeded the use time of consumers. Traditional failure modes such as creep and fatigue caused by heat, electricity, and magnetism are no longer the main concerns of manufacturers. . Vibration and drop are unavoidable during transportation and use. Vibration during transportation and accidental drop during use are the key factors affecting the life of electronic products.

Drop tests are often divided into three test methods: product level, board level and connector level. Product-level tests are often used by manufacturers to test their drop resistance performance after the actual production of electronic products, evaluate the actual service life in terms of drops, and improve the design of the overall structure of electronic products; board-level and connector-level tests mainly tend to The laboratory studies the failure mechanism and life prediction of solder joints under different drop environments. However, the joint-level drop test only focuses on the failure mechanism of a single solder joint, ignoring the relevance of the actual product. Therefore, the board-level drop test is the main research of many scholars. direction. In order to ensure that the research results can be used as a reference for other scholars, JCDEC formulated detailed drop test standards in 2003, which described the shape, size, and BGA position of PCB boards in detail. However, the standards have certain limitations for experimental research. , it is not conducive to observe the failure modes of different positions of the solder joints during the drop process. The failure process of the solder joints is mainly observed through electrical signals, which leads scholars to pay too much attention to the influence of mechanics on the solder joints during the research process, ignoring the impact of the properties of the material itself on the drop. The role of life, and in the simulation process, the actual experimental verification is relatively little. In order to study the relationship between the failure mechanism and the material of the solder joint at the board level, it is an indispensable direction to improve the accuracy of life prediction. Therefore, designing a PCB board that can observe the failure process of solder joints has become one of the key issues in the study of board-level drop reliability. Due to the thin thickness and large area of the PCB board, it is not conducive to the placement in the process of grinding and polishing and electron microscope testing. It is mainly solved by the method of mounting samples, which will destroy the integrity of the PCB board and cannot guarantee the actual solder joints. In-situ observation of PCB boards, designing a supporting jig that is conducive to the grinding, polishing and observation of PCB boards is also one of the key issues that need to be solved.

Contents of the invention

The problem to be solved by the present invention is to overcome the technical defects described above, and to design a PCB board and its supporting jig that can observe the failure process of solder joints during the drop process while ensuring the board-level drop test requirements.

A drop test PCB board and supporting jig, characterized in that: PCB board 1 is a square, and a daisy chain 2 is arranged in the middle of each side of the square, and the diameter of the lead wire 4 on the daisy chain 2 and the diameter of the solder ball The dimensions are nearly equal, the start and end pads 3 of the leads 4 on the daisy chain 2 are located in the middle of the PCB 1, and four corners of the PCB 1 are arranged for fixing the PCB 1 on the drop platform. Hole 5; the supporting fixtures for the PCB include grinding and polishing fixtures and electron microscope test fixtures. The grinding and polishing fixtures include upper plate surface 6 and lower plate surface 7, which are connected by hinge 15; groove III9 is located on the lower plate surface The middle position on the left side of 7, the groove IV10 is located at the upper middle position of the lower board surface 7, the size of the groove III9 and the groove IV10 is the same as that of the BGA packaged on the PCB 1, that is, the ball grid array structure size, and the groove I11 is located at the bottom The middle position on the right side of the board, the groove II12 is located in the middle of the lower side of the lower board; the groove I11 and the groove II12 are rectangular, and the vertical dimension of the groove I11 and the groove II12 is 1 smaller than that of the package BGA mm, the protruding end I13 is located on the left side of the lower plate 7, the protruding end II14 is located on the upper side of the lower plate 7, the screw hole 8 is located at the lower right of the grinding and polishing fixture, and the upper plate 6 and the lower plate are fixedly connected by screws face 7;

The bottom of the electron microscope test fixture is composed of a cuboid and two circular arcs. Ten card slots 16 are evenly distributed above the cuboid. The size of the card slots can meet the vertical insertion of the PCB board packaged with BGA into the card slots.

The size of the PCB board 1 is 41mm*41mm*0.5mm.

The present invention can achieve the following beneficial effects: the PCB board designed by the present invention can be used to study the initiation, expansion and disconnection of cracks on the solder joints on the PCB board during the drop process, the design is simple, and it is beneficial to laboratory scientific research. Its supporting fixture, The grinding and polishing fixture can ensure the uniform level of the entire row of solder joints on the PCB during the grinding and polishing process, and reduce the plastic deformation of the PCB. The grinding and polishing efficiency is high, the operation is simple, the work intensity is reduced, and the repeatability and stability of the experiment are guaranteed. The electron microscope test fixture can complete the observation of the microstructure of the solder joints without damaging the PCB board, and the number of samples observed at one time is large.

Description of drawings

Figure 1: Schematic diagram of PCB board structure;

Figure 2: Schematic diagram of the structure of the grinding and polishing fixture;

Figure 3: Rear view of grinding and polishing fixture

Figure 4: Schematic diagram of the structure of the electron microscope test fixture;

In the figure: 1-PCB board, 2-daisy chain, 3-beginning and ending pads, 4-leads, 5-holes, 6-upper board, 7-lower board, 8-screw holes, 9-lower board Groove I, 10-lower plate groove II, 11-lower plate groove III, 12-lower plate groove IV, 13-lower plate extension I, 14-lower plate extension II, 15-hinge , 16-card slot.

specific implementation

A drop test PCB board, which includes a PCB board 1, the PCB board 1 is a cube, the size is 41*41*0.5mm, and a daisy chain 2 is arranged in the middle of each side of the square, and the daisy chain 2 The diameter of the upper lead 4 is nearly equal to the diameter of the solder ball. The start and end pads 3 of the daisy chain 2 lead 4 are located in the middle of the PCB 1, and four corners of the PCB 1 are arranged for connecting the PCB 1 Fixed to the hole 5 on the drop table. The matching jigs include grinding and polishing jigs and electron microscope testing jigs, and the grinding and polishing jigs include an upper plate surface 6 and a lower plate surface 7, which are connected by a hinge 15. Lower board groove III9 and lower board groove IV10 are located on the left side and upper side of lower board surface 7, and the size is the same as that of the package BGA ball grid array structure BGA on PCB board 1, lower board groove I11 and lower board groove II12 Located in the middle of the right side and the lower side of the lower board surface 7, it is rectangular, and the vertical dimension is 1 mm smaller than that of the package BGA. The lower board extension I13 and the lower board extension II14 are located on the left side of the lower board And the upper side, the screw hole 8 that is positioned at the lower right, is fixedly connected with the upper and lower panels by screws. The bottom of the electron microscope test fixture is composed of a cuboid and two circular arcs. Ten card slots 16 are evenly distributed above the cuboid. The size of the card slots can meet the vertical insertion of the PCB packaged with BGA into the card slots.

Specific operation process:

The PCB board 1 shown in Figure 1 can be directly manufactured by the manufacturer according to the circuit diagram and dimensions described above, the finished PCB board is packaged with BGA, installed according to the grinding and polishing jig shown in Figure 2, unscrew the screws, and open the upper board surface 6 , Lower board surface 7, let the BGA package face down, put it into the grinding and polishing fixture, ensure that the PCB board is completely horizontally placed on the lower board surface 7, BGA and lower board groove I9 lower board groove II-10, lower board The groove III11 and the groove IV12 of the lower board are completely matched, and both sides are horizontally connected with the extension end I13 of the lower board and the extension end II14 of the lower board, and the upper and lower boards are fixed by screws to ensure that the PCB board is installed horizontally In the jig; after the grinding and polishing is completed, insert the PCB board into the structure of the electron microscope test fixture as shown in Figure 4 to ensure that there is no contact between the grinding and polishing surface and the electron microscope test fixture, and put the electron microscope test fixture into the sample table for testing. Scanning test to observe the original shape of the microstructure of solder balls, after that, connect the PCB board to the drop test bench for drop test, combined with electrical signals, when crack initiation is found, remove the PCB board and put it into the electron microscope In the test fixture, observe the changes of the cracks in the microstructure and reciprocate in this way until the BGA completely fails. During this process, the initiation, expansion and disconnection of the cracks in the solder joints can be thoroughly observed.

Claims (2)

1. a supporting jig for drop test PCB board, it is characterized in that: PCB board (1) is a square, all arranges daisy chain (2) in the middle position of each limit of square, the lead wire on the daisy chain (2) ( 4) is nearly equal to the diameter of the solder ball, and the start and end pads (3) of the leads (4) on the daisy chain (2) are located in the middle of the PCB (1), on the PCB (1) ) are arranged with holes (5) for fixing the PCB board (1) on the drop table; the supporting fixtures for the PCB board include grinding and polishing fixtures and electron microscope test fixtures, and the grinding and polishing fixtures include the upper plate Surface (6) and lower panel surface (7), the two are connected by hinge (15); groove III (9) is located in the left middle position of lower panel surface (7), groove IV (10) is located in the lower panel At the middle position on the upper side of the surface (7), the size of groove III (9) and groove IV (10) is the same as that of the BGA packaged on the PCB (1), that is, the structure size of the ball grid array, and the groove I (11) is located at the bottom The middle position on the right side of the board, the groove II (12) is located in the middle of the lower side of the lower board; the groove I (11) and the groove II (12) are rectangular, the groove I (11) and the groove The vertical dimension of the slot II (12) is 1 mm smaller than that of the package BGA, the protruding end I (13) is located on the left side of the lower board (7), and the protruding end II (14) is located at the bottom of the lower board (7) On the upper side, the screw hole (8) is located at the bottom right of the grinding and polishing fixture, and the upper plate (6) and the lower plate (7) are fixedly connected by screws; The bottom of the electron microscope test fixture is composed of a cuboid and two arcs, and 10 slots (16) are evenly distributed above the cuboid, and the size of the slots can meet the vertical insertion of the PCB board of the package BGA into the slots. 2. A supporting jig for a drop test PCB board according to claim 1, characterized in that: the size of the PCB board (1) is 41mm*41mm*0.5mm.