Screening method for electrolytic capacitors that maintains individual capacitor unit identity

Patent metadata

Field	Value
Publication number	US-11448680-B2
Application number	US-202117218374-A
Country	US
Kind code	B2
Filing date	Mar 31, 2021
Priority date	Mar 31, 2020
Publication date	Sep 20, 2022
Grant date	Sep 20, 2022

Abstract

A method of screening a lot of capacitors is provided. The method includes measuring a first leakage current of each individual capacitor in a first set of capacitors and calculating a first mean leakage current; removing each of the individual capacitors having a measured first leakage current equal to or above a first predetermined value, forming a second set of capacitors; subjecting the second set of capacitors to a burn in treatment; measuring a second leakage current for each of the individual capacitors in the second set and calculating a second mean leakage current; comparing the second leakage current for each of the individual capacitors to the first leakage current for each of the individual capacitors; and removing each of the individual capacitors having a second leakage current equal to or above a second predetermined value and/or having a second leakage current that does not change by a specified amount compared to the first leakage current for each of the individual capacitors.

First claim

What is claimed is:

1. A method of iteratively screening a lot of electrolytic capacitors having a predetermined rated voltage, the method comprising:
measuring a first leakage current of each individual capacitor in a first set of capacitors in the lot and calculating a first mean leakage current therefrom;
removing each of the individual capacitors from the first set that have a measured first leakage current equal to or above a first predetermined value, thereby forming a second set of capacitors, the first predetermined value being equal to one or more standard deviations above the first mean leakage current;
subjecting the second set of capacitors to a burn in treatment, wherein the burn in treatment comprises applying a predetermined test voltage to the capacitors;
after the burn in treatment, measuring a second leakage current for each of the individual capacitors in the second set of capacitors and calculating a second mean leakage current therefrom;
comparing the second leakage current measured for each of the individual capacitors in the second set to the first leakage current measured for each of the individual capacitors in the second set; and
removing from the lot each of the individual capacitors from the second set that have a second leakage current equal to or above a second predetermined value and/or that have a second leakage current that does not change by a specified amount compared to the first leakage current measured for each of the individual capacitors, thereby forming a third set of capacitors, the second predetermined value being equal to one or more standard deviations above the second mean leakage current, wherein each of the capacitors in the first set is located in a unique position on a carrier plate on a leakage current measurement apparatus, further wherein each of the individual capacitors in the second set of capacitors is maintained in its respective unique position on the carrier plate on the leakage current measurement apparatus, further wherein the carrier plate is positioned on the leakage current measurement apparatus in the same manner as when the first leakage current was measured.

2. The method of claim 1 , wherein the first leakage current is determined at a temperature ranging from 20° C. to 150° C.

3. The method of claim 1 , wherein the first predetermined value is equal to three or more standard deviations above the first mean leakage current.

4. The method of claim 1 , wherein the burn in heat treatment occurs for a time period ranging from 25 hours to 75 hours.

5. The method of claim 1 , wherein the predetermined test voltage ranges from 0.8 to 1.2 times the predetermined rated voltage.

6. The method of claim 1 , wherein the burn in heat treatment is conducted at a temperature ranging from 100° C. to 150° C.

7. The method of claim 1 , wherein the second leakage current is determined at a temperature ranging from 20° C. to 150° C.

8. The method of claim 1 , wherein the second predetermined value is equal to three or more standard deviations above the second mean leakage current.

9. The method of claim 1 , further comprising soldering the first set, second set, and/or third set of capacitors via a reflow process.

10. The method of claim 9 , wherein the reflow process occurs in a convection oven at a peak temperature profile ranging from 200° C. to 280° C.

11. The method of claim 9 , wherein the second set of capacitors are soldered via the reflow process, wherein the soldering occurs between the burn in heat treatment and the second leakage current measurement.

12. The method of claim 9 , wherein the third set of capacitors are soldered via the reflow process.

13. The method of claim 1 , further comprising the steps of:
measuring a third leakage current of the third set of capacitors and calculating a third mean leakage current therefrom; and
removing capacitors from the third set that have a measured third leakage current equal to or above a third predetermined value and/or that have a third leakage current that does not change by a specified amount compared to the second leakage current measured for each of the individual capacitors, the third predetermined value being equal to one or more standard deviations above the third mean leakage current.

14. The method of claim 13 , wherein the third leakage current is determined at a temperature ranging from 15° C. to 35° C., and wherein the third predetermined value is equal to three or more standard deviations above the third mean leakage current.

15. The method of claim 1 , wherein the leakage current measurement apparatus includes a positioning guide for ensuring accurate positioning of the carrier plate requiring that the carrier plate be positioned in the same manner for each iteration of leakage current testing.

16. The method of claim 15 , wherein the positioning guide includes a portion having a geometry that corresponds with a geometry of a portion of the carrier plate to ensure that the carrier plate is correctly oriented.

17. The method of claim 1 , further wherein the carrier plate includes a unique identifier to track the capacitors located on the carrier plate.

18. The method of claim 1 , wherein each of the individual capacitors in the third set of capacitors is maintained in its respective unique position on the carrier plate on the leakage current measurement apparatus, further wherein the carrier plate is positioned on the leakage current measurement apparatus in the same manner as when the second leakage current was measured.

19. The method of claim 1 , wherein the capacitors are solid electrolytic capacitors or wet electrolytic capacitors.

Assignees

• Avx Corp
• Kyocera Avx Components Corp

Inventors

• Bernier Howard
• Yocz Daniel
• Vaillancourt Glenn
• Laforge Jason

Classifications

• G01R31/016 Primary

  Testing of capacitors (measuring capacitance G01R27/2605) · CPC title

• G01R31/2849

  Environmental or reliability testing, e.g. burn-in or validation tests (of individual semiconductors G01R31/2642; of printed circuits boards G01R31/2817; of IC's G01R31/2855) · CPC title