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Method for preventing misorientation by using a keyed through-hole mount electrolytic capacitor

IP.com Disclosure Number: IPCOM000006574D
Publication Date: 2002-Jan-15
Document File: 5 page(s) / 53K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for preventing misorientation by using a keyed through-hole mount electrolytic capacitor. Benefits include

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Method for preventing misorientation by using a keyed through-hole mount electrolytic capacitor

Disclosed is a method for preventing misorientation by using a keyed through-hole mount electrolytic capacitor. Benefits include

General description

              The disclosed method includes an alternate design for through-hole mount electrolytic capacitors and their circuit board mounting holes so that misoriented insertion or backwards polarity is prevented.

              The key elements of the method include:

•             Enlarging one of the two leads of a through hole mount capacitor

•             Enlarging one of its two mounting holes to ensure that capacitor is inserted with the                 correct polarity

              Through-hole mount electrolytic capacitors are conventionally inserted into circuit boards by hand prior to mass soldering. The capacitors are cylindrical in shape with two leads protruding from one of the flat ends of the cylinder. These polarized devices must be inserted properly for them to function properly. Because the two leads are identically sized and symmetrically located on the end of the body, they can physically be inserted in two different orientations, of which only one is correct. The body is marked in some way to indicate which lead is the positive lead and which lead is negative. Although these capacitors are marked to indicate their polarity, and boards are marked to indicate the required polarity, the capacitor is sometimes inserted backwards. If it is inserted incorrectly, the circuit may not function properly. In addition, incorrectly oriented electrolytic capacitors pose a fire hazard in the factory and in a customer product because they can overheat and burn.

Detailed description

              No conventional solution prevents misoriented insertion of through-hole mount electrolytic capacitors. However, several approaches reduce the chance of misorientation and detect misorientation. Electrolytic capacitors can be purchased with leads of two different lengths. The insertion operator learns to insert the longer lead into the correct hole, and then inserts the shorter lead into the other hole. This method does not prevent misorientation. It also requires that the leads be trimmed to proper length after soldering. Pre-trimmed parts cannot be used with this method.

              Automated insertion machines, instead of people, can be used to insert electrolytic capacitors. The cost of these machines cannot be justified in low labor cost areas. The component packaging commonly used for these machines can be loaded into the machine backwards, resulting in all the capacitors being inserted backwards. Therefore, automated insertion cannot prevent misorientation.

              Misorientation can be detected by manual (visual) inspection after mass soldering but is not 100% effective. Misoriented parts must be reworked. This approach does not address misoriented insertion but can reduce the number of misoriented parts leaving the factory.

              Misorientation can also be detected by automated visual inspection after mass soldering...