Micro welding spot combination daisy chain evaluation method

Abstract

The invention provides a micro welding spot combination daisy chain evaluation method. Compared with the prior art, the reliability evaluation problem caused by different micro-welding-spot interconnection modes is solved, direct connection, bending and rotating micro-welding-spot configuration daisy chains are given, and transverse verification and comparison are carried out according to different conductive cross sections and different failure times of welding spots in typical interconnection configurations. The method can be applied to evaluation of a process stage and verification in the high-reliability application field, and is beneficial to improving the reliability of a micro welding spot technology in the aerospace high-reliability field.

Description

Technical Field

[0001] The invention relates to the field of three-dimensional stacked integration reliability assessment, and in particular to a micro solder joint combination daisy chain assessment method. Background Art

[0002] At present, microelectronics has entered the post-Moore era. The growth rate of traditional reliance on advanced process nodes to improve the performance of components has slowed down significantly. Stacking multiple chips and realizing high-density chip packaging interconnection through advanced packaging technology is the main technical route to maintain the continuous increase in the functional density of integrated circuits. Micro solder joints of different scales such as C4 and C2 are usually used as vertical interconnection structures to realize the electrical interconnection and heat exchange of the lower two layers of chips and the chip and the adapter board. Therefore, the micro solder joints need to withstand the combined electrical and thermal stress and produce corresponding degradation. In addition, the complex internal interconnection morphology of the chip may cause the local stress of the three-dimensional stacked integrated microsystem chip to increase, which will be damaged prematurely in the high-reliability aerospace stress environment. It is particularly necessary to identify the weak links of the typical morphology of micro solder joints and evaluate the reliability of micro solder joints under different interconnection morphologies for high-reliability 3D microsystem components for aerospace applications.

[0003] Generally, a straight-through daisy chain is used to evaluate the electrothermal reliability of micro solder joints. However, due to the complexity of the internal interconnection of 3D microsystems, the interconnection architecture of solder joints includes multiple angles. The current seeking the shortest path at different angles will cause the solder joints to experience edge-collecting current stress. Only a straight-through daisy chain cannot be used to evaluate the various interconnection situations of solder joints and interconnection lines of aerospace high-reliability 3D microsystem components. Different daisy chain paths have different failure times.

[0004] Therefore, there are difficulties in the above technical fields that cannot be solved using existing technologies, which hinder the continued reliable application of higher density 3D microsystems built using micro solder joints in aerospace or high-reliability applications. Summary of the invention

[0005] The object of the present invention is to provide a micro solder joint combination daisy chain evaluation method to solve the problems existing in the prior art.

[0006] In order to solve the above technical problems, the technical solution of the present invention is to provide a micro solder joint combination daisy chain evaluation method, comprising the following steps:

[0007] S1, Construction of a micro solder joint combination daisy chain evaluation device;

[0008] S2. Place four groups of samples in a nitrogen-filled chamber, and select at least 6 samples from each group; set the temperature to 25°C, 85°C, 125°C, and 175°C, and apply a constant current. Switch the power-on time through a diode. When the three structures have high failure paths, each channel is powered on for at least 1 hour in a single cycle. The cumulative time of different stages of the total cycle is 300 hours, 600 hours, 1500 hours, and 3000 hours. At the end of each stage, the continuity and resistance value of the path are tested. The resistance value change rate exceeds the limit value of 10% or an open circuit or short circuit occurs.

[0009] S3. Place four groups of samples in a nitrogen-filled chamber, with no less than 12 samples in each group. Set the temperature to 25°C, 85°C, 125°C, and 175°C, apply a constant current, and select a single channel through a diode. In the single-channel daisy chain failure time evaluation experiment, use the time statistics method for 50% device failure, and the resistance value change rate exceeds the limit value of 10% or an open circuit or short circuit occurs;

[0010] S4. If an over-limit failure or burnout occurs in steps S2 and S3, it is necessary to switch to the other two channels to test and verify whether the input terminal is degraded or burned.

[0011] Furthermore, the step S1 includes:

[0012] S1-1, the paths of micro solder joints in the 3D microsystem are divided into three typical straight-through, bending, and rotation configurations. A single input terminal 1 is used to switch three channels through three PIN diodes. The control end of the PIN is led out through control lines 5, 6, and 7, and the on and off of the three paths are controlled by voltage signals;

[0013] S1-2, the micro solder joint 8 is located between the upper and lower substrates, the top substrate is a silicon substrate, and the bottom substrate is selected from silicon, organic substrate or ceramic substrate according to the evaluated packaging level, and the bottom external interconnection line is not shielded by the top silicon substrate;

[0014] S1-3, the daisy chain structure of a single micro solder joint includes a top substrate 11, a top solder pad 13, a solder ball 8, a bottom solder pad 14, and a bottom substrate 12. Two adjacent micro solder joints are interconnected through the copper strip line on the top substrate or the bottom substrate to form a series relationship. The straight daisy chain 2 repeats the series relationship along a straight line, wherein the edge spacing of the solder joint is at least the diameter of the solder joint. The angle of each adjacent bending line of the bent daisy chain 3 is 90°, and the lead wire is finally led out through the bottom substrate; the rotating daisy chain 4 has a rotating structure of 90°, and adopts a rotating path design from outside to inside, and the lead wire is finally led out of the rotating daisy chain 4 through the bottom substrate;

[0015] S1-4, the solder joint and the top or bottom copper tape interconnection include a solder pad 13, a transition copper tape 14 and a copper tape line 15 that bears a large current.

[0016] S1-5. According to the size of the solder joint, the width of the input and output lead-out terminals of the underlying interconnecting copper strip wire and the current tolerance to be evaluated, select a gold wire or a gold strip to lead out the electrical signal of the evaluation device.

[0017] The beneficial effects achieved by the micro solder joint combination daisy chain evaluation method provided by the present invention are:

[0018] Compared with the prior art, the present invention solves the problem of reliability evaluation after interconnection of different micro solder joints. The method provides three types of micro solder joint configurations: straight-through, bent, and rotated daisy chains, and conducts horizontal verification and comparison for different conductive cross-sections and failure times of solder joints in typical interconnection configurations. The method can be applied to the evaluation of process stages and verification in high-reliability application fields, which helps to improve the reliability of micro solder joint technology in the aerospace high-reliability field. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention will be further described below in conjunction with the accompanying drawings:

[0020] Figure 1 These are the three types of daisy chain configurations;

[0021] Figure 2 This is a partial enlarged picture of the upper and lower layers of the daisy chain.

[0022] Figure 3 This is a partial enlarged cross-sectional view of the micro solder joint daisy chain up and down transfer

[0023] Figure 4 is a top view of the package including the daisy chain. DETAILED DESCRIPTION

[0024] The micro solder joint combination daisy chain evaluation method proposed by the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0025] Example 1

[0026] 1. Design of verification device

[0027] (1) The paths of micro solder joints in 3D microsystems are divided into three typical configurations: straight-through 2, bending 3, and 90° left-handed rotation 4 (e.g. Figure 1 As shown), a single input terminal 1 is used to switch three channels through three PIN diodes, and the control terminal of the PIN is led out through control lines 5, 6, and 7 and controlled by a voltage signal.

[0028] (2) The micro solder joint is located between the upper and lower substrates ( Figure 3 ), the top substrate 11 is a silicon substrate, and the bottom substrate 12 is a silicon, organic substrate or ceramic substrate according to the evaluated packaging level (chip and silicon, silicon and organic substrate, silicon and ceramic substrate) Figure 4 ), the external lead-out interconnection lines on the bottom layer are not shielded by the top silicon substrate.

[0029] (3) The daisy chain structure of a single micro solder joint is Figure 1 The micro solder joints include solder balls and pads. Two adjacent micro solder joints are connected by copper strips on the top substrate or the bottom substrate ( Figure 4 The top layer 13 and the bottom layer 14 are interconnected to form a series relationship, and the straight daisy chain 2 repeats the series relationship along a straight line by adding solder joints and the same belt line, wherein the side-to-side spacing of the solder joints is at least the diameter of the solder joints. The angle of each adjacent bending line of the bent daisy chain 3 is 90°, and the lead wire is finally led out through the bottom substrate (bent daisy chain 9). The rotating daisy chain 4 has a rotating structure of 90°, and adopts a rotating path design from outside to inside, and the lead wire is finally led out of the rotating daisy chain 4 through the bottom substrate.

[0030] (4) Select gold wire or gold tape according to the size of the solder joint and the width of the underlying interconnecting copper tape line to lead out the electrical signal of the evaluation device.

[0031] Second, four groups of samples were placed in a nitrogen-filled chamber, and at least 6 samples were selected for each group. The temperature was set to 25°C, 85°C, 125°C, and 175°C, and a constant current was applied. The power-on time was switched through the diode. Each channel was powered on for at least 1 hour in a single cycle. The cumulative time in different stages of the total cycle was 300 hours, 600 hours, 1500 hours, and 3000 hours. The continuity and resistance value of the path were tested during the above time. The resistance value change rate exceeded the limit value of 10% or an open circuit or short circuit occurred. The failure time of the three structures was compared.

[0032] 3. Place four groups of samples in a nitrogen-filled chamber, with no less than 12 samples in each group. Set the temperatures to 25°C, 85°C, 125°C, and 175°C, apply a constant current, and select a single channel through a diode. In the single-channel daisy chain failure time evaluation experiment, a 50% device failure time statistical method is used. The failure standard is that the resistance value change rate exceeds the limit by 10% or an open circuit or short circuit occurs.

[0033] 4. If over-limit failure or burnout occurs in steps 2 and 3, it is necessary to switch to the other two channels to test and verify whether the input end is degraded or burned out.

[0034] The contents not described in detail in this specification belong to the prior art known to those skilled in the art. It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention.

Claims

1. A method for evaluating a micro solder joint combination daisy chain, characterized in that: The steps include: S1, Construction of a micro solder joint combination daisy chain evaluation device; S2. Place four groups of samples in a nitrogen-filled chamber, and select at least 6 samples from each group; set the temperature to 25°C, 85°C, 125°C, and 175°C, and apply a constant current. Switch the power-on time through the diode. When the three structures have high failure paths, each channel is powered on for at least 1 hour in a single cycle. The cumulative time of different stages of the total cycle is 300 hours, 600 hours, 1500 hours, and 3000 hours. During the above time, the continuity and resistance value of the path are tested. The resistance value change rate exceeds the limit value of 10% or an open circuit or short circuit occurs; S3. Place four groups of samples in a nitrogen-filled chamber, with no less than 12 samples in each group. Set the temperature to 25°C, 85°C, 125°C, and 175°C, apply a constant current, and select a single channel through a diode. In the single-channel daisy chain failure time evaluation experiment, use the time statistics method for 50% device failure, and the resistance value change rate exceeds the limit value of 10% or an open circuit or short circuit occurs; S4. If an over-limit failure or burnout occurs in steps S2 and S3, it is necessary to switch to the other two channels to test and verify whether the input end is degraded or burned out.

2. The micro solder joint combination daisy chain evaluation method according to claim 1, characterized in that: The step S1 comprises: S1-1, the paths of micro solder joints in the 3D microsystem are divided into three typical straight-through, bending, and rotation configurations, a single input terminal 1 is used to switch three channels through three PIN diodes, the control end of the PIN is led out through the control line (5, 6, 7), and the on and off of the three paths are controlled by voltage signals; S1-2, the micro solder joint (8) is located between the upper and lower substrates, the top substrate is a silicon substrate, and the bottom substrate is selected from silicon, organic substrate or ceramic substrate according to the evaluated packaging level, and the external interconnection line of the bottom layer is not shielded by the top silicon substrate; S1-3, the daisy chain structure of a single micro solder joint includes a top substrate (11), a top solder pad (13), a solder ball (8), a bottom solder pad (14), and a bottom substrate (12). Two adjacent micro solder joints are interconnected through the copper strip line on the top substrate or the bottom substrate to form a series relationship. The straight daisy chain (2) repeats the series relationship along a straight line, wherein the side-to-side spacing of the solder joints is at least the diameter of the solder joints. The angle of each adjacent bending line of the bent daisy chain is 90°, and the lead wire is finally led out through the bottom substrate; the rotating daisy chain has a rotating structure of 90°, and adopts a rotating path design from outside to inside, and the lead wire is finally led out of the rotating daisy chain (10) through the bottom substrate; S1-4, the interconnection between the solder joint and the top or bottom copper strip line includes a solder pad (13), a transition copper strip (14) and a copper strip line (15) that bears a large current; S1-5. According to the size of the solder joint, the width of the input and output lead-out terminals of the underlying interconnecting copper strip wire and the current tolerance to be evaluated, select a gold wire or a gold strip to lead out the electrical signal of the evaluation device.

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