JP2018098444A - Electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic device capable of carrying out quality inspection of an object to be inspected such as solder ball while avoiding characteristics fluctuation of the element.SOLUTION: An electronic device 10 includes: a circuit board 16 which has a first face in a first direction and a second face in a second direction opposite to the first direction; an IC chip 12 disposed on the first face of the circuit board; an object to be inspected 24 disposed on the second face of the circuit board; a reference circuit 14 disposed on the IC chip; a circuit 30 other than the reference circuit disposed on the IC chip; and a shield 26 which covers the first direction side of the reference circuit but does not cover the first direction side of the circuit other than the reference circuit, and which can shield X-ray.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electronic device.

  In the manufacturing process and mounting process of semiconductor devices, by observing the transmitted image of the semiconductor device by irradiating radiation such as X-rays, etc., observation of the adhesive surface in solder mounting of semiconductor components, etc., and observation of the connection state of the connector cable, etc. As described above, a defect inspection is performed at a site that cannot be observed directly by visual observation or the like. It is known that the characteristics of elements in a semiconductor device may fluctuate when the semiconductor device is irradiated with strong radiation such as X-rays. Therefore, there is a technique for absorbing or attenuating radiation energy by providing a metal filter so as to shield the chip of the semiconductor device, thereby suppressing fluctuations in characteristics of elements in the semiconductor device.

  However, on the other hand, when there is an electrode on the back of the package, such as BGA (Ball Grid Array) and QFN (Quad Flatpack No Lead), etc., when checking the defect of the adhesive surface during solder mounting by X-ray transmission image In addition, if X-rays are shielded by an X-ray shielding filter to protect the element, there is a problem that an X-ray transmission image on the back surface of the package cannot be obtained, so that a defect check cannot be performed.

JP 2006-202791 A JP 2012-134642 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an electronic device that avoids and corrects variations in element characteristics and enables a work-inspection by X-ray transmission of an inspection object such as a solder ball. Is to provide.

  According to the invention described in claim 1, the electronic device (10) includes a circuit board (16) having a first surface in a first direction and a second surface in a second direction opposite to the first direction. ), An IC chip (12) provided on the first surface of the circuit board, an object to be inspected (24) provided on the second surface of the circuit board, and a reference circuit ( 14), a circuit (30) other than the reference circuit arranged on the IC chip, and a first direction side of the reference circuit, and a first direction side of the circuit other than the reference circuit is not covered, X And a shield (26) capable of shielding the line.

  According to this structure, the area | region which does not arrange | position a solder ball can be minimized by minimizing the installation range of an X-ray shield. In addition, when performing a solder ball performance inspection using an X-ray transmission image, the shielding area is not irradiated with X-rays. Therefore, if there is a solder ball in this area, an X-ray transmission image cannot be obtained and the inspection cannot be performed. . However, in this embodiment, since an object to be inspected (solder ball) is not arranged in the shielding area, it is possible to avoid a situation in which the inspection of the solder ball cannot be performed by the X-ray transmission image. Further, since the reference circuit is not irradiated with X-rays, the characteristics of the circuit elements arranged in the reference circuit do not change. Therefore, the correction signal can be correctly generated by the reference circuit by correcting the characteristic variation of the circuit to be adjusted using the reference circuit. Thereby, normal circuit operation of the whole electronic device can be secured.

1 is a top view illustrating a schematic configuration of an electronic device according to a first embodiment. 1 is a longitudinal sectional view showing a schematic configuration of an electronic device according to a first embodiment. 1 is a bottom view showing a schematic configuration of an electronic device according to a first embodiment. Diagram showing a schematic configuration example of the shield Diagram showing a schematic configuration example of the shield Diagram showing a schematic configuration example of the shield Diagram showing a schematic configuration example of the shield Schematic plan view schematically showing the electrical configuration of the electronic device Schematic configuration example of comparator and difference adjustment circuit Schematic configuration example of comparator and difference adjustment circuit Example of schematic configuration of adjustment circuit Example of schematic configuration of adjustment circuit The top view showing the schematic structure of the electronic device concerning a 2nd embodiment. A longitudinal sectional view showing a schematic configuration of an electronic device according to a second embodiment The bottom view which shows schematic structure of the electronic device which concerns on 2nd Embodiment.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In the following embodiments, common or related elements or substantially the same elements are denoted by the same reference numerals, and description thereof is omitted. Further, in the following description, when “X-rays are not irradiated”, not only when the X-rays are completely shielded but also at a level at which the influence of the X-rays is not affected, that is, the element characteristics do not change. This includes the case where X-rays have been attenuated and irradiated.

(First embodiment)
1 to 3 are diagrams showing a schematic configuration of the electronic device 10 according to the first embodiment. FIG. 1 is a plan view, FIG. 2 is a longitudinal sectional view of a portion along the line AA in FIG. It is a back view. As shown in FIGS. 1 to 3, the electronic device 10 includes an IC chip 12, a circuit board 16, a sealing resin 18, solder balls 24, and a shield 26.

  The electronic device 10 is a so-called IC package. As shown in FIG. 2, the IC chip 12 is fixed to the chip mounting surface of the circuit board 16, that is, the upper surface side (first surface) in the drawing. An electrode (not shown) is provided on the back side of the chip mounting surface of the circuit board 16, that is, on the opposite side (second surface) of the chip mounting surface, and a plurality of solder balls 24 for external connection are formed on this electrode. Has been. The circuit board 16 is configured by arranging wiring made of a conductive material such as copper on an insulating base material mainly made of resin or ceramics.

  The IC chip 12 includes elements such as transistors, diodes, resistors, and capacitors integrated on a semiconductor substrate such as silicon, and a circuit such as a logic circuit, a memory circuit, an A / D conversion circuit, an amplifier circuit, or a mixed circuit thereof ( A large-scale integrated circuit) is configured and formed into a chip. In the present embodiment, the IC chip 12 having a substantially planar shape is bonded and fixed to the chip mounting surface of the circuit board 16.

  On the IC chip 12, a reference circuit 14 and other adjusted circuits 30a, 30b, 30c, and 30d (hereinafter collectively referred to as the adjusted circuit 30) are formed. In the present embodiment, the reference circuit 14 includes a circuit element used for adjusting the characteristic variation of the circuit 30 to be adjusted other than the reference circuit 14, and the characteristic variation of the circuit element is caused by X-ray irradiation. In some cases, circuit elements that do not recover the expected function even if the characteristic variation is corrected are included. The reference circuit 14 refers to a portion that affects the overall performance of the electronic device 10 when a characteristic variation occurs due to X-ray irradiation, such as a memory or a reference power supply. Specifically, a comparator 32, a memory 34, a reference power supply circuit 36, a difference adjustment circuit 38, and the like, which will be described later, are included.

  On the other hand, the circuit 30 to be adjusted includes a circuit element that is subjected to adjustment of the characteristic variation by the reference circuit 14 and when the characteristic variation of the circuit element occurs due to the X-ray irradiation, the characteristic variation is not corrected. The circuit element that exhibits the expected circuit function, or the circuit element that recovers the expected circuit function by correcting its characteristic variation. The circuit 30 to be adjusted is a circuit that is unlikely to affect the overall performance of the electronic apparatus 10 even if characteristic variation occurs due to X-ray irradiation, or a circuit that can adjust the characteristic variation, for example, control logic, ON / OFF driver, COMP threshold value, FB gain. Means.

A shield 26 is formed above the reference circuit 14 so as to cover the upper surface side of the reference circuit 14. The shield 26 does not cover the upper surface side of the circuit 30 to be adjusted. The reference circuit 14 is included in a region projected downward of the shield 26, that is, a shielding region 28. The shield 26 has a function capable of shielding by absorbing, reflecting, or attenuating X-rays. Examples of the constituent material of the shield 26 include metal materials such as Al, Cu, W, Ag, Ti, Sn, Pb, Ta, Mo, Ge, Bi, Pt, and Zn, alloys containing these metals, or Mo. A multilayer film using / Si, a silicon nitride film (Si ₃ N ₄ ), or the like can be used. Here, a region projected vertically downward in the drawing of the shield 26 is defined as a shielding region 28. Note that “shielding” includes not only shielding by absorbing X-rays but also reflecting or scattering X-rays, and the X-ray intensity is reduced to a level at which variations in element characteristics can be avoided. Including attenuation.

  The circuit board 16 is configured by arranging wirings made of a conductive material such as copper in multiple layers on an insulating base material mainly made of resin or ceramics. A plurality of lands (not shown) are formed on the chip mounting surface of the circuit board 16, and these lands are electrically connected to electrode pads (not shown) on the IC chip 12 by bonding wires 22.

  On the back surface of the circuit board 16, the solder balls 24 are formed in a lattice shape, that is, a matrix shape, except for the shielding region 28. That is, the solder ball 24 is not disposed in the shielding region 28. The solder ball 24 is electrically connected to a land formed on the chip mounting surface via a wiring (not shown) formed on the circuit board 16 and is electrically connected to a circuit formed on the IC chip 12. Provide electrical connection function. As the solder ball 24, for example, a solder material having a composition such as Sn—Ag, Sn—Ag—Cu, Sn—Zn—Bi, or Sn—Cu can be used. The solder ball 24 is formed in a spherical shape, that is, a ball shape. Thus, the electronic device 10 is a BGA (Ball Grid Array) type package.

  In the present embodiment, the shield region 28 is provided so as to shield only the reference circuit 14 and protect it from X-ray exposure, thereby minimizing the X-ray shielding region 28. Further, the solder ball 24 is not disposed in the shielding region 28. As a result, the area where the solder balls 24 can be arranged is increased, and a workmanship inspection using an X-ray transmission image of the solder balls 24 is made possible.

  The upper surface of the IC chip 12 is covered and sealed with the sealing resin 18 including the bonding wires 22 and the shield 26. As a constituent material of the sealing resin 18, a material such as an epoxy resin to which a phenolic curing agent, silicone rubber, and a filler are added can be used.

Next, a method for forming the shield 26 will be described with reference to FIGS.
4 shows that the shield 26 is formed by stacking the second and third wiring layers 42b and 42c using the first wiring layer 42a as the circuit wiring among the multilayer wirings used in the IC chip 12. FIG. The shield 26 is configured to be arranged on the reference circuit 14.

  FIG. 5 shows a shield 26 that is configured by further providing a fourth wiring layer 42 d for forming the shield 26 and disposing it on the reference circuit 14. In this case, a unique film thickness can be set and the film thickness can be increased.

  FIG. 6 shows a CoC (Chip on Chip) structure in which an IC chip 12 a is further arranged on the IC chip 12, and the IC chip 12 a is arranged on the reference circuit 14. The IC chip 12a is provided with a wiring layer 42 on its upper part, and further on its upper part is provided with a shield 26 formed of a metal layer. An insulating layer (not shown) is provided between the wiring layer 42 and the shield layer 26. In this case, the IC chip 12a, the wiring layer 42, and the shield 26 function as an X-ray shield, and the shielding effect is improved by the presence of the IC chip 12a and the wiring layer 42 as well as the shield 26.

  In FIG. 7, a wiring layer 42 and a shield 26 formed of a metal film are formed on the reference circuit 14. An insulating layer (not shown) is provided between the wiring layer 42 and the shield layer 26. In this case, the shield 26 is formed by, for example, a metal film formed by a coating film such as silver paste, a metal film formed by local film formation by FIB (Focused Ion Beam), or solder printing. A metal film can be used.

  FIG. 8 is a schematic plan view schematically showing an electrical configuration of the electronic device 10 according to the embodiment. The IC chip 12 includes a comparator 32, a memory 34, a reference power supply circuit 36, and a difference adjustment circuit 38, which constitute the reference circuit 14. The reference circuit 14 is covered by a shield 26 and is shielded from X-rays. Has been. Therefore, the reference circuit 14 is not irradiated with X-rays.

  The IC chip 12 includes adjusted circuits 30a, 30b, and 30c and adjusting circuits 40a, 40b, and 40c. Since the circuit to be adjusted 30 is not covered with the shield 26, the circuit characteristics may be changed by being irradiated with X-rays. The adjustment circuit 40 is a circuit for adjusting the characteristics of the circuit to be adjusted 30 and is connected so that an adjustment signal from the reference circuit 14 can be input.

  The reference circuit 14 adjusts the characteristics of the circuit to be adjusted 30 by generating an adjustment signal to the adjustment circuit 40 and outputting the adjustment signal to each adjustment circuit 40. The comparator 32 compares the characteristic before the change of the adjusted circuit 30 with the characteristic after the change. The characteristic before the change of the adjusted circuit 30, that is, the initial characteristic is stored in the memory 34, and the comparator 32 calls the initial characteristic of the adjusted circuit 30 from the memory 34 and uses it for comparison. The reference power supply circuit 36 is a circuit for generating a reference internal voltage, and is also used for comparing the characteristics after the X-ray irradiation of the adjusted circuit 30 with the initial characteristics.

  The difference adjustment circuit 38 receives the comparison result of the element characteristics from the comparator 32, determines a variation from the initial characteristic of the circuit 30 to be adjusted, generates an adjustment signal for correcting the variation from the initial characteristic, and adjusts the difference. It functions as a determination control unit that outputs to the circuit 40. The adjustment circuit 40 corrects the element characteristics of each circuit to be adjusted 30 based on the input adjustment signal. The difference between the corrected element characteristic and the initial characteristic is determined again by the comparator 32 and the difference adjustment circuit 38, and the adjustment is finished when the difference is equal to or less than a predetermined value.

  9 and 10 show configuration examples of the comparator 32 and the difference adjustment circuit 38. FIG. The configuration shown in FIG. 9 is an example in which the comparator 32 and the difference adjustment circuit 38 are configured by analog circuits, and the reference power supply voltage from the reference power supply circuit 36 and the signal from the circuit to be adjusted 30, that is, the analog value, are output by the comparator 32. The difference adjustment circuit 38 outputs an adjustment signal corresponding to the difference to the adjustment circuit 40.

  The configuration shown in FIG. 10 is an example in which the comparator 32 and the difference adjustment circuit 38 are configured by digital circuits, and the initial characteristics from the memory 34 and the signal from the circuit to be adjusted 30 are converted into A / D by the A / D conversion circuit 33. The converted signals are compared by the difference adjustment circuit, and an adjustment signal corresponding to the difference is generated and output to the adjustment circuit 40. In this case, the difference adjustment circuit 38 also serves as the comparator 32.

  11 and 12 show a configuration example of the adjustment circuit 40. FIG. The adjustment circuit 40 shown in FIG. 11 has a configuration in which a plurality of stages of resistors are provided in series and a switch is provided in parallel with each resistor. By switching each switch by the difference adjustment circuit 38, the output value of the adjustment circuit 40 is adjusted. The adjustment circuit 40 illustrated in FIG. 12 includes a plurality of stages of resistors in series, and includes a connection line that connects between each resistor and an output line, and includes a switch in the middle. The output value of the adjustment circuit 40 is adjusted by switching each switch by the difference adjustment circuit 38.

  According to the above configuration, the shield 26 is disposed so as to cover only the upper part of the reference circuit 14, so that the installation range of the X-ray shield can be minimized. Thereby, the area | region which does not arrange | position the solder ball 24 can be minimized. In addition, when the workmanship inspection of the solder ball 24 arranged on the back surface of the electronic device 10 is performed by analysis of the X-ray transmission image, the reference circuit 14 is shielded by the shield 26 and thus is not irradiated with X-rays. In this case, X-rays are irradiated vertically downward from above as shown by arrows in FIG. Further, the solder ball 24 is not disposed in the shielding region 28. From the above, an X-ray transmission image cannot be obtained because the shielding area 28 is not irradiated with X-rays. However, since the solder ball 24, that is, the inspection object is not arranged in the shielding area 28, the X-ray transmission image can be obtained. It is possible to avoid the situation where inspection is not possible. Accordingly, there is no region where the inspection of the solder ball 24 cannot be performed. Further, since the reference circuit 14 is not irradiated with X-rays, the characteristics of the circuit elements arranged in the reference circuit 14 do not change. Therefore, it is possible to correctly generate the adjustment signal for correcting the characteristic variation of the circuit to be adjusted 30 using the reference circuit 14. As a result, normal circuit operation of the entire electronic device 10 can be ensured.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. The electronic device 10 according to the second embodiment is different from the first embodiment in that a shielding region 28 by the shield 26 is disposed at an end portion of the electronic device 10. As shown in the figure, an example in which the solder ball 24 is arranged in the shielding area 28 arranged at the end of the electronic device 10 is shown, but the solder ball 24 is arranged in the shielding area 28 as in the first embodiment. You may comprise so that 24 may not be arrange | positioned. In the electronic device 10 according to the second embodiment, the IC chip 12 and the solder ball 24 are electrically connected by the through electrode 23 instead of the bonding wire 22.

According to the second embodiment, the same effect as the first embodiment is obtained. In addition, since the shield 26, that is, the shielding area 28 is disposed at the end of the electronic device 10, even if the solder ball 24 is disposed in the shielding area 28, it is possible to visually inspect the workmanship of the solder ball 24. Further, the workmanship inspection of the solder ball 24 may be performed by optical image processing, analysis of reflected / scattered light by laser irradiation, or the like without using visual observation. Similarly to the first embodiment, when the solder ball 24 is not disposed in the shielding region 28, the solder ball 24 does not exist in the shielding region 28 where the X-ray is shielded, so that the result is obtained by the X-ray transmission image. It is possible to avoid the situation where inspection is not possible.
(Other embodiments)
As shown in FIG. 2 or FIG. 4, the shield 26 has been described with reference to the example in which the shield 26 is disposed above the IC chip 12 in the sealing resin 18 in the figure, but is not limited thereto. For example, the electronic device 10 may be disposed on the upper surface of the sealing resin 18. Moreover, you may arrange | position to the downward direction of the IC chip 12, and the back surface of the electronic apparatus 10, and may be arrange | positioned both above and below. When the shield 26 is disposed below the IC chip 12, the IC chip 12 can be shielded against X-ray irradiation from below.

  Further, although the BGA package has been described as an example, the present invention is not limited to this. For example, the present invention can be applied to all products in which electrodes are arranged on the back surface of the electronic device 10, such as a QFN package, an LGA (Land grid array) package, or a SON (Small-Outline No Lead) package.

  Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

  DESCRIPTION OF SYMBOLS 10 ... Electronic device, 12 ... IC chip, 14 ... Standard circuit, 24 ... Solder ball (inspection object), 26 ... Shield (shielding object), 28 ... Shielding area, 30, 30a, 30b, 30c, 30d ... Circuit 32... Comparator (comparator) 34. Memory (storage unit) 36. Reference power supply circuit 38. Difference adjustment circuit (determination control unit) 40, 40 a, 40 b, 40 c.

Claims (10)

A circuit board (16) comprising a first surface in a first direction and a second surface in a second direction opposite to the first direction;
An IC chip (12) provided on the first surface of the circuit board;
A test object (24) provided on the second surface of the circuit board;
A reference circuit (14) disposed on the IC chip;
Circuits other than the reference circuit (30, 30a, 30b, 30c, 30d) arranged on the IC chip,
An electronic device (10) comprising: a shield (26) capable of shielding X-rays that covers the first direction side of the reference circuit and does not cover the first direction side of circuits other than the reference circuit.   2. The electronic device according to claim 1, wherein the object to be inspected is not arranged in a shielding area (28) that is an area in which the shielding object is projected in the second direction.   The electronic device according to claim 1, wherein the shielding region is located at an end portion of the circuit board.   4. The electronic device 10 according to claim 1, wherein the reference circuit includes a circuit (32, 34, 36, 38) used for adjusting a characteristic variation of a circuit other than the reference circuit. 5.   5. The circuit according to claim 1, wherein the reference circuit includes a circuit (32, 34, 36, 38) that does not recover the expected function even when the characteristic variation occurs due to the X-ray irradiation. The electronic device according to any one of the above.   The electronic device according to claim 1, wherein the shield includes a metal or an alloy.   The electronic device according to claim 6, wherein the metal or alloy includes at least one of Al, Cu, W, Ag, Ti, Sn, Pb, Ta, Mo, Ge, Bi, Zn, Mo, and Pt.   The reference circuit includes a storage unit (34) that stores initial characteristics of circuits other than the reference circuit, a comparison unit (32) that compares initial characteristics and characteristics after variation of circuits other than the reference circuit, and the comparison An electronic device according to any one of claims 1 to 7, further comprising: a determination control unit (38) that determines a result of the unit and generates an adjustment signal.   The adjustment signal (40, 40a, 40b, 40c) which adjusts the characteristic variation of circuits other than the above-mentioned reference circuit based on the inputted adjustment signal is inputted into the adjustment signal generated by the judgment control part. The electronic device described.   The electronic device according to claim 1, wherein the object to be inspected is a solder ball (24).

Images