JPH01173884A - Diagnosis and overlay for electronic circuit - Google Patents

Abstract

PURPOSE: To detect a defective part rapidly by aligning at least one of a plurality of temperature-sensitive capsule liquid crystal zones on an overlay to at least one of a plurality of electronic components on an electronic circuit. CONSTITUTION: A plurality of overlays 23 that are constituted equally for each circuit board 11 are prepared on operation. For example, when the board 11 is operated under changing temperature conditions, a series of overlays 23 are displayed in color properly under different range of temperature conditions. When a defective integrated circuit exists, the temperature of a defective component exceeds its normal operating temperature in most cases. In this case, a temperature-sensitive zone does not appear in green but appear in higher- spectrum color on color spectrum, namely blue or violet. Therefore, if the component is defective, it can be easily observed that the color of a liquid crystal differs from green that indicates a normal operation, thus easily identifying the defective component.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to diagnostic circuits for electronic components, and in particular to electronic circuit boards that utilize a plurality of encapsulated liquid crystal zones that provide a color display in response to temperature changes. A diagnostic overlay is provided for this purpose.

(Prior Art and Problems) Electronic circuits generally include transistors, resistors, delay elements, and integrated circuits (rlcJs) or chips. It consists of jl operating electronic components. The IC is ROM5. Includes memory chips, drivers, receivers, gates and microprocessors. ICs perform various tasks and are classified based on their 7f miscellaneousness, e.g. the relative ? j! Depending on the degree of miscellaneousness, small scale accumulation (rssz), medium scale accumulation (rMs)
IJ ), large scale integration (rLsIj), or very large scale integration (rVLS IJ) type ICs. The speed at which an IC processes signals can vary between direct current (DC) levels and frequencies of several megahertz and higher.

Voltage,? Various error parameters such as lt flow are determined at the time of manufacturing and are generally stated as ranges in the manufacturer's specifications in the form of maximum limits, minimum limits, and representative values. Waveforms processed by ICs can be divided into digital or analog.

While analog waveforms can take any shape, digital waveforms are essentially rectangular waves. Various factors, including the functional integrity of the electronic components, prevent a true square wave from becoming a true square wave. In order to maintain the operating characteristics of the entire electronic circuit, each integrated circuit must operate normally.

Defects in the operation of components on the board will change the operating characteristics of the board, and if these changes become large enough, the operational characteristics will also become defective, leading to destruction of the desired electronic response of the circuit as a whole.

Determining the source of problems in these electronic circuits is difficult. Generally, the source is a defective component, but determining which component on the board is at fault is a tedious task. Traditionally used diagnostic tools are complex, difficult to operate, typically non-portable, and expensive. Second, when performing an 111 recovery on-site, it is important to avoid system failure, and on-site engineers are under pressure to return the system to normal operation without delay. For this reason, there is a strong tendency to replace boards or subsystems on a prospective basis and leave the work of actually confirming failures to a board 1.1 laboratory.

Upon arrival at Boat 111, the boards are sorted and
1 Failures occur repeatedly before the work is completed. This procedure is time-consuming, expensive, and causes fluctuations in the inventory level of spare boards, which makes it difficult to implement the "just-in-time" inventory control principle.

Thermal image analysis testing method is the industry accepted method for detecting electronic components with anomalous thermal properties.

For proven circuit designs, the defects are typically faulty ICs or board artifacts, while for new circuit designs, the above methods can be used to identify substandard components or insufficient design ventilation. method can be used.

Predicting the thermal activity of electronic components involves complex calculations involving numerous variables and parameters that often cannot themselves be easily measured or predicted. Although mathematical models have been devised to describe electronic components under controlled laboratory conditions, no practical general formulas have been provided that can predict the operating temperature of an IC under all circumstances. In general, predictions regarding thermal activity must be made based on extrapolation of data obtained by subringing good parts operating under various fixed conditions.

For a certain amount of DC power dissipated in the semiconductor, the junction temperature reaches a value determined by factors such as the thermal conductivity of the chip support material and the temperature difference with the environment. Motorol
a A 1 cation Not, e AN-50
9, the junction temperature under steady-state conditions can be calculated using the following formula: T(j) = P(d)neR(stdy) +
T(aml+) However, T(j): Junction temperature P(d) = Power consumption R at the junction
aml)): The above equation is only valid for DC power at thermal equilibrium. Under dynamic conditions, the duty cycle analysis must take into account the thermal response of the system; the junction temperature at the end of the pulse train is determined by the sum of the average temperature rises, as cooling occurs between pulses. must not be equal to . Therefore, the following formula is applicable: T(jav) −T(c) = R(jc) zero P
(d) where T(jav) = average junction temperature rise T(
c) = Chip case temperature R (jc) = Thermal resistance between junction and case P (tl)"
DC power b = duty cycle To further complicate matters, the concept of duty cycle is based on the existence of a stable pulse train of the same square wave, but such a condition is often not found in real electronic circuits. There is no such thing. Most waveforms are somewhat non-rectangular and vary in frequency and period.

Among the various damage mechanisms that occur in electronic components, many are associated with variations in power density as a cause or effect. As can be seen from the above equation, such tJ11! The mechanism is ultimately linked to changes in temperature. That is, some mechanism that changes the net level of power consumption causes the operation of the electronic component to become defective, and such defects are of sufficient magnitude and duration to change the external surface temperature of the electronic component. and the change in temperature recorded at the outer surface represents the relative extent of the defect. Furthermore, the elevated temperature event may constitute a damage mechanism resulting in secondary failure.

SUMMARY OF THE INVENTION According to one feature of the invention, an overlay is positioned in substantial contact with electronic circuitry, and at least one of a plurality of temperature-sensitive liquid crystal encapsulation zones on the overlay comprises: an electronic circuit comprising aligning with at least each respective one of a plurality of electronic components on the electronic circuit and observing a color of the temperature sensitive encapsulated liquid crystal zone while the electronic circuit is under operation for a predetermined period of time; A diagnostic method is provided.

According to another feature of the invention, at least one temperature-sensitive encapsulation aligned with a respective component of said electronic circuit in an overarray positioned in substantial contact with said at least one electronic component of said electronic circuit. An overarray is provided comprising liquid crystal zones, the temperature sensitive encapsulated liquid crystal zones color indicating a predetermined temperature of the component.

According to yet another feature of the invention, a plurality of temperature sensitive microencapsulated liquid crystal zones located within each region of the overlay are provided, each of the zones exhibiting substantially the same color at each of a plurality of operating temperatures. , an overlay for an electronic circuit is provided in which each of the zones becomes a different color when each of the plurality of operating temperatures changes by a predetermined amount.

According to yet another feature of the invention, a microencapsulated liquid crystal zone is provided which is contactable with at least one electronic component and provides a color indication of a predetermined temperature of the electronic component.

Specific embodiments of the invention will now be described, by way of example only, with reference to the drawings.

EXAMPLE Referring first to FIG. 1, a printed circuit motherboard from an IBN PC personal computer is generally indicated at 10. This is the boat 11 itself and the RO
It consists of M512, a RAM chip 13, and various parts such as gates including the gate shown as 21. The various components are attached to the printed circuit board 1 at various distances, depending on the overall circuit and the design of the various components, as can be seen in Figure 1.
It protrudes outward from 1.

The diagnostic overlay is shown generally at 23 in FIG. The overlay 23 is formed of transparent Mylar and supports a plurality of temperature sensitive zones 25, each consisting of a plurality of microcapsules 26'h), each capsule 26 containing a number of color temperature sensitive liquid crystals 27. . The microencapsulated liquid crystal is shown more clearly in FIG. Liquid crystal microcapsules 26 are adhesively secured within temperature sensitive zones 25 of overlay 23, with each zone 26 corresponding to the location of a heat source zone, typically a central area of an integrated circuit or electronic component on circuit board 11.

For example, FIG. 2 shows indexing rectangles each surrounding the temperature sensing zones of different sized integrated circuits, such as 5fl. The size of each rectangle corresponds to the size of each component desired to be contacted, and the location of the rectangle is equal to the location of the component on printed circuit board II.

For example, temperature sensing zone 24 corresponds to integrated circuit 30 on board 11, temperature sensing zone 35 corresponds to integrated circuit 32, and temperature sensing zone 33 corresponds to integrated circuit 34. The color of each temperature sensing zone on overlay 23 corresponds to the normal operating temperature of its respective S-product circuit on printed circuit board 11 and is designed to be the same under normal operation.

FIG. 3 shows a printed circuit board 11 containing the general components of an integrated circuit 36 and a carrier 40 shown extending outwardly therefrom. overlay 23
schematically shows temperature known zones 25 in which microcapsules 26 each supporting a liquid crystal 27 are placed.
is located.

Temperature sensing zone 25 is shown just before contacting integrated circuit 36 .

The various parts located on board ll project outward from the boat 11 at different distances. To allow contact between each series of parts and overlay 23 having the same height, overlay 23 is divided into sections.

Two such sections 45, 46 are shown in FIG. These and other sections may be overlaid 23 via perforations or the like so that they can be positioned on components of the same height or on their associated circuit boards 11.
It can also be separated from.

Referring now to FIG. 5, not only is the diagnostic overlay 23 divided into different sections, but the overlay 23 does not correspond to the electronic components on the printed circuit board 14 of FIG.
3 further comprising a temperature sensitive liquid crystal encapsulation zone 50 on top of the temperature sensitive liquid crystal encapsulation zone 50. This separate zone 50 is provided in each of a plurality of overlays 23, each overlay 23 being designed for the same printed circuit board, but at the same time
are used at different ambient temperatures. Another zone 50 of interest is shown in its overlay 2 at a particular ambient temperature.
Visually indicates when 3 is available.

The visual indication may be, for example, a color such as green, or rUsE when the ambient temperature is appropriate for a particular overlay.
ME (please use this)" as a reading character such as 1'4.

A color standard chart 51 may also be used on overlay 23, as shown in FIG. color standard chart)
51 is a simple comparator that compares the color of the liquid crystal on top of the electronic component. This is useful, for example, when viewing the overlay 23 under different lighting conditions, such as outdoors or natural lighting conditions and in-layer or artificial lighting conditions. Char+51 is not temperature sensitive, and the colors in chart 51 are arranged in the same order as the liquid crystal color changes as the temperature of a particular electronic component changes.

(Work) During operation, a plurality of overlays 23 having the same configuration are prepared for each circuit board 11, respectively. However, as previously mentioned, each overlay 23 is configured to be used in a different range of ambient temperatures, e.g.
1 is operated under varying temperature conditions, each of the series of overlays 23 is configured to display the correct color under a different range of temperature conditions. For this,
Said another liquid crystal encapsulation zone 50 (FIG. 5) has a pH of 1
to ensure that the particular overlay 23 is the correct one to use under the particular ambient temperature conditions.

An indication signal such as green or a visible message indicates zone 50.
When appearing above, the presence of such a color or visible message indicates to the user that that particular overlay 23 is the correct one to use.

After selecting the correct overlay 23, each temperature sensing zone 25 on the overlay 23 is positioned opposite a corresponding integrated circuit such that, for example, the indexing rectangle of FIG. 2 surrounding the temperature sensing zone is 1:1 with the respective integrated circuit. In a relationship. Overlay 23 is then brought into contact with circuit board 11. The 1:1 relationship between the rectangle surrounding the temperature sensing zone and the outermost surface of each integrated circuit is to facilitate alignment or indexing.

When there is a series of components with different heights than the rest of the components on the circuit board 14, as in the example shown in FIGS. 4 and 6, the indexing rectangle uses perforations, along with their respective temperature sensing zones. Alternatively, it can be separated from overlay 23 by cutting as shown in FIG. The correct operating voltage is then applied to the circuit and
The color of the temperature sensitive zone is observed after a certain time depending on the ambient temperature. For example, RO on a printed circuit board ll
The correct operating temperature for the M-chip 12 is between approximately 24°C and 26°C after 1 minute of operation at an ambient temperature of 20°C, approximately 24°C.
It is known that C is optimal.

The corresponding nocturnal crystal is designed to be green within this operating temperature range. Similarly, the operating temperature of RAM chip 13 is known to be between 23.5°C and 24°5C under the same conditions. The corresponding 1ffl crystal is also designed to be green when the chip is operating at the correct temperature.

However, when a component is not operating properly, ie, in the presence of a defective integrated circuit, the defective component will most likely rise above its normal operating temperature. In this case, the temperature sensitive zone will not appear green, but its color will generally be higher on the color spectrum, for example blue or violet. Outside the visible range, the liquid crystal appears black. When the temperature is lower than the correct operating temperature of the component, as in some defective operating characteristics, the color of the liquid crystal will generally be on the lower end of the color spectrum, eg red or brown. Similarly, black can be used at lower ranges. Therefore, if a component is defective, it is easily observed that the color of the liquid crystal differs from the green color that indicates normal operation, and such a component can be quickly identified.

The components of an electronic circuit generally interact strongly, and the presence of a fault in one component often changes the power level, and thus the operating temperature, of another component with which it is interacting. In this case, the faulty part is first displayed flexibly, followed by a color change in another part. As a general rule, the first component recognized should be considered the most critical.

After replacing that part, the circuit is tested again.

Under different lighting conditions, the color of the capsule or liquid crystal zone 25 will appear differently. In this case, to help determine the correct color, the user can use the color standards chart 51.
(see Figure 5).

Color standard chart 51 is of course not temperature sensitive, and each color of chart 51 is arranged in the same order as the color change that a particular liquid crystal zone 25 exhibits as temperature changes.

Many modifications to the specific embodiments described above are currently contemplated. For example, a colored rectangle surrounding a temperature sensitive zone is not necessary, as it is only used to correctly determine the temperature sensitive zone relative to the corresponding electronic component. Also, the bins that extend between the overlay and the circuit board,
Any number of indexers can be used for proper alignment, including rectangular openings for other parts.

Although the illustrated overlay has been described as being made from transparent mylar, such construction is also used with the rectangles for alignment purposes only.

If indexing is performed using other methods, the overlay may be opaque or colored as desired.

This is not the only point that the temperature should be read at a specific point in time after applying the correct operating voltage to the board at a certain ambient temperature. For example, a temperature-time graph could be provided that provides the correct reading point for each ambient temperature. This means that the overlay can be used over a wide range of ambient temperatures. Additionally, only a thermometer may be attached to the overlay 23 to ensure that the ambient temperature is correct when observing color changes.

Although the liquid crystal zone 25 has been described as having almost the same shape as the part to be tested, the zone 25 can be defined as only a small portion of the area of various separated rectangles 53, such as a circle 52, as shown in FIG. Of course it's good too.

Similarly, although the overlay 23 has been described as a separate component from the printed circuit and the electronic components that constitute the printed circuit,
The overarray 23 can be permanently affixed to circuitry, or a plurality of individual liquid crystal encapsulation zones can be used, each permanently affixed to a particular electronic component, to provide an embedded or permanent imaging system for alignment. It is also possible to eliminate the need.

Many other modifications may be made to the above-described apparatus, and the specific embodiments described herein are to be considered as illustrative only and not as limitations on the scope of the invention, which is defined by the following claims. be.

[Brief explanation of the drawing]

FIG. 1 is a partial isometric view of a typical printed circuit board used in the IBM PC personal computer; FIG. 2 is a plan view of a diagnostic overarray according to the present invention used in the printed circuit board of FIG. 1; FIG. 3 is a schematic cross-sectional enlarged view of one integrated circuit on a circuit board, including an overlay of FIG. 2 shown in operation; FIG. 4 is a partial isometric view of another printed circuit board similar to FIG. 5 is a top view of a plurality of diagnostic overarrays used in the printed circuit board of FIG. 4; and FIG. 6 is a partial isometric view of the circuit board of FIG. 4 in which the overarray of FIG. 6 is used. FIG. 11.14...Electronic circuit (boat), 12.13.2
1.30, 32.34.3G...Circuit parts, 23...
・Overlay, 24.25.33... Temperature sensitive encapsulated liquid crystal zone, 26... Microcapsule, 27
...Liquid crystal, 51...Color standard chart, 53...
- Indexing means (rectangle). FIG, 4 FIG, 5

Claims (1)

[Claims] 1. Positioning the overlay in substantial contact with the electronic circuit;
aligning at least one of a plurality of temperature sensitive encapsulated liquid crystal zones on the overlay with at least a respective one of a plurality of electronic components on the electronic circuit, while the electronic circuit is under operation for a predetermined period of time; , a method for diagnosing an electronic circuit comprising observing the color of said temperature sensitive encapsulated liquid crystal zone. 2. The method of claim 1, wherein said overlay is transparent. 3. The method of claim 2, wherein said overlay is made of Mylar. 4. The method of claim 3 further comprising determining the position of said mylar overlay relative to said electronic circuit. 5. selecting a corresponding one of a plurality of overlays usable in the same electronic circuit by reference to another temperature sensitive encapsulated liquid crystal zone, wherein said another zone is one of the plurality of overlays for each of the plurality of overlays; The method of claim 1 as provided in claim 1. 6. The method of claim 5, further comprising comparing the observed color of the zone to a set of color standards present on the overlay. 7. The method of claim 1, further comprising comparing the observed color of the zone to a set of color standards present on the overlay. 8. further comprising selecting the applicable one of a plurality of overlays available for use with the same electronic circuit by reference to another temperature sensitive encapsulated liquid crystal zone, wherein said another zone is a respective one of the plurality of overlays; The method of claim 7 as provided in claim 7. 9. in an overarray positioned in substantial contact with at least one electronic component of an electronic circuit, at least one component aligned with a respective component of said electronic circuit;
an overarray comprising two temperature sensitive encapsulated liquid crystal zones, said temperature sensitive encapsulated liquid crystal zones color indicating a predetermined temperature of said component. 10. Claim 10, wherein said overlay comprises a plurality of said temperature sensitive encapsulated liquid crystal zones, each of said temperature sensitive encapsulated liquid crystal zones having a visible color in response to a predetermined temperature of a respective component of said electronic circuit. Overarray of term 9. 11. Each of the temperature sensitive encapsulated liquid crystal zones comprises:
11. The overarray of claim 10, wherein the overarray is substantially the same color after a specified period of time when each zone is at a first predetermined temperature. 12. The overarray of claim 11, wherein each of said temperature sensitive encapsulated liquid crystal zones exhibits a visually observable color change when said first predetermined temperature changes by a predetermined value. 13. The overarray of claim 12 further comprising alignment indexing means on said overlay. 14. Claim 1, wherein the overlay is transparent.
3-term overlay. 15. The overlay of claim 14, wherein said overlay is made of Mylar. 16. The overlay of claim 9, wherein said overarray is affixed to said electronic component. 17. The overlay of claim 9, further comprising another temperature sensitive encapsulated liquid crystal zone, said another zone being color responsive to changes in ambient temperature. 18. The overlay of claim 17 further comprising a series of color standards on the overlay. 19. The overlay of claim 9 further comprising a series of color standards on the overlay. 20. The overlay of claim 9, further comprising another temperature sensitive encapsulated liquid crystal zone, said another zone being color responsive to changes in ambient temperature. 21. The overlay of claim 9, further comprising another temperature sensitive encapsulated liquid crystal zone, said another zone being color responsive to changes in ambient temperature. 22, comprising a plurality of temperature sensitive microencapsulated liquid crystal zones located within each region of the overlay, each of the zones exhibiting substantially the same color at each of the plurality of operating temperatures; An overlay for electronic circuits in which the color of each zone changes when the color changes by a predetermined amount. 23. The overlay of claim 22, further comprising another temperature sensitive microencapsulated liquid crystal zone, said another zone being color responsive to changes in ambient temperature. 24. The overlay of claim 23 further comprising a series of color standards on the overlay. 25. A microencapsulated liquid crystal zone contactable with at least one electronic component and color indicating a predetermined temperature of said electronic component.