Browse Prior Art Database

CONTACTING TEST MECHANISM WITH FIXED BASE

IP.com Disclosure Number: IPCOM000008549D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-24
Document File: 3 page(s) / 124K

Publishing Venue

Motorola

Related People

Mohd Yusairi Idris: AUTHOR

Abstract

SOIC packages, such as SOT23, are manufac- tured in large amounts each week. Electrical testing for these devices requires fast and effective equip- ment. Today, there are many methods of testing them either after leads are trimmed and formed or before leads are formed.

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MOTOROLA Technical Developments

CONTACTING TEST MECHANISM WITH FIXED BASE

by Mohd Yusairi ldris

INTRODUCTION

  SOIC packages, such as SOT23, are manufac- tured in large amounts each week. Electrical testing for these devices requires fast and effective equip- ment. Today, there are many methods of testing them either after leads are trimmed and formed or before leads are formed.

One fast testing method is known as Contact Test, which tests the units after they are formed and

singulated from the frame. This method is used in ISMECA's design taping machine. The Contact Test requires each unit to be placed from the top position of the testing area (Figure la). The unit's leads must make contact with the test blade in order for electrical current to get through to the die for an electrical test. Therefore, the unit is required to be pressed down onto the test blade to make sure a good and effective contact is made. However, by pressing the lead onto the test blade, the chances of creating a lifted lead (coplanarity issue) is increased.

I

'ick Up Tip

Test Station 81 Pin Height set up

Screw

Push UD-

Push Up Spring

Station Dowel -.

Fig. la Contact Test Layout (side view)

PROBLEM DESCRIPTION bending displacement. An increase in blade dis- placement creates an increase in the blade's elastic During the Contact Test process, a lead faces a force and reacts on the lead. This can cause serious reaction force produced by the blade's elastic force. damage to the lead coplanarity.

The reaction force is proportional to the blade

0 Moloda. ItIC. 19Y8 55 March I998

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MOTOROLA Technical Developments

  Furthermore, there is no guard or prevention whatsoever to limit the unit's travel, so as to prevent an excessive elastic force produced by the blade. It totally depends on the thrustor bar's length and the test site height set-up.

  An initial study shows that SOT23 lead bend threshold is in the range of I80 to 260 gram force, while the test blade displacement (for beryllium

capable of producing 2 10 to 308 gram force (elastic force) respectively (Figure 1 b). Thus, only 0.1 mm varies the force through blade displacement. Therefore, the numbers show why human skill and feel jeopardise the lead coplanarity if the ela...