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MaxQFP J-Lead Inspectable Joint Feature

IP.com Disclosure Number: IPCOM000234562D
Publication Date: 2014-Jan-17
Document File: 3 page(s) / 226K

Publishing Venue

The IP.com Prior Art Database

Abstract

Common quad flat leaded packages (QFP) have the external leads or terminals formed in a J-shape and/or a gull wing. For the former, the leads are folded towards the package body whereas for the latter, the leads are shaped away from the package body. These two types of leaded packages (J-lead or gull wing) are common and can be seen in many electronic appliances. Less common but available are are packages that have both J-leads and gull-wing shaped leads. The solder joint between the lead and the application board can be easily seen from the spread of the solder material either with the naked eye or low power optical scope. The ability to see the solder is necessary to ensure there is sufficient solder coverage to prevent premature board joint failure. For packages with both J-lead and gull wing leads, solder joint inspection is more challenging.

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TITLE

MaxQFP J-Lead Inspectable Joint Feature

ABSTRACT

Common quad flat leaded packages (QFP) have the external leads or terminals formed in a J-shape and/or a gull wing. For the former, the leads are folded towards the package body whereas for the latter, the leads are shaped away from the package body. These two types of leaded packages (J-lead or gull wing) are common and can be seen in many electronic appliances.  Less common but available are are packages that have both J-leads and gull-wing shaped leads.  The solder joint between the lead and the application board can be easily seen from the spread of the solder material either with the naked eye or low power optical scope. The ability to see the solder is necessary to ensure there is sufficient solder coverage to prevent premature board joint failure. For packages with both J-lead and gull wing leads, solder joint inspection is more challenging.

CONTENT

We proposed a forming a trench or channel on the J-leads of the lead frame to improve the ability for solder joint inspection. The J-lead is fabricated such that it has a half-etched trench at the middle of the lead. The depth of the trench is about half the total thickness of the lead.  Figure 1 shows the half etched trench formed on alternate rows of the leads, as viewed from the topside of the lead frame. The half etched trench is made on rows where the leads are formed into the J shape only. On the alternate rows where the leads are shaped into a gull wing, there is no half etched trench feature.

Figure 1 Half etched trench feature

For rigidity purposes and ensuring that the lead does not crack during the forming process, the half etched trench does not extend to the tip of the lead. The trench stops about 1 to 2mm from the tip as illustrated in figure 2.

Figure 2 Length of the half etched trench on the J lead

The trench...