2009 International Symposium on Microelectronics - Second Bond Stitch Width Model - A Trend Solution for Lead Width Reduction

Sep 5, 2026

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A semiconductor miniaturization trend drives rising IO connection counts while sharply reducing lead width, creating critical second-bond wire-stitch width challenges. When stitch width approaches or exceeds the lead width, second-bond stitch pull results degrade in both average performance and process stability. A JMP (ver. 7.0) model is introduced to predict second-bond stitch width from capillary dimensions and wire diameter, enabling optimized designs, verification testing, and a stitch-width formulation identifying wire diameter and tip size as major contributors.

LanguageEnglish

CategoryPresentations

FormatPDF

Pages7

Reading Time3 min

AccessFree to download

Overview

Problem context: ultra fine pitch and second-bond challenges

Modeling approach and verification

Abstract

Trend and motivation

JMP model and optimization matrix

Experimental Procedure

DOE and plug-and-play setup

2009 International Symposium on Microelectronics Second Bond Stitch Width Model as a Trend Solution for Lead Width Reduction Tomer Levinson1, a, Menache Alon 1, b, Shi Fei 2, c 1 Kulicke & Soffa Bonding Tools PO Box 90 Yokneam Elite, Israel 20692 2 Kulicke & Soffa (SuZhou) Limited No. 255 Hong Middle Road Suzhou Industrial park, Suzhou 215021 P.R.C [a](atlevinson@kns.com)[tlevinson@kns.com](atlevinson@kns.com);[b](bamenache@kns.com)[amenache@kns.com](bamenache@kns.com);[c](cfeshi@kns.com)[feshi@kns.com](cfeshi@kns.com) Abstract A well known trend in the semiconductor industry is miniaturization while continuously increasing the number of Input Output (IO) connections. This trend introduces new Wire bonding (WB) challenges in the second bond arena, known as the second bond stitch width. As the stitch width scale gets closer to the lead width, the need to accurately predict the second bond width becomes crucial. In order to answer this new need a JMP (ver.7.0) model for second bond stitch width in correlation to the capillary dimensions and Wire Diameter (WD) is introduced. Different designs with changing geometries were optimized, bonded, and measured for their stitch width responses. Geometries such as: Hole (H), Chamfer Diameter (CD), Tip size (Tip), Face Angle (FA), Outer Radius (OR) and WD are part of the tested matrix. A verification test was conducted and custom capillary designs were produced based on a numerical formulation from the model in order to receive a specific stitch width. These capillary designs were bonded and measured in order to verify the credibility of the stitch width model. An important observation out of few interesting results showed, that the main contributors controlling the second bond stitch width are the WD and Tip. Additionally a stitch width formulation as a function of the main capillary geometries and WD is introduced. Key words: wire bonding, capillary design, wire diameter reduction, fine pitch leads, and model. Overview The demand for miniature devices with a large I/O count has become a fundamental requirement in many assembly houses. This ongoing need has pushed substrate design to have an increasing lead count while at the same time minimization of the lead width. For instance a body size of 30mm with approximately 200, 600 I/O is usually expected to have 0.5mm, 0.2mm maximum lead pitch respectively. If higher I/O is needed an even smaller lead pitch is expected and for today's ultra fine pitch packages they can get as small as 100µm with even smaller stitch width [1; 2] . This high demand for ultra small width of lead pitch has brought the lead width to a near proportion as to the 1st bond pad dimension and in rare cases has been seen as low as 40µm lead width. These extremely narrow leads have brought new challenges into the wire bonding industry particularly in regards to the second bond. If, in the past, the main challenges of the second bond were the adhesion of the stitch, the tail area and the intensity of the tool mark, today new measures (e.g. stitch width) are starting to be an important factor when optimizing a second bond process. If the stitch width is larger than the lead width it is expected to have degradation in the second bond stitch pull results. The degradation is expected both in the average results and in the stability of the process. As wire bonding is a peripheral process surrounding the die in all directions the stitch direction also is changeable around the die. This peripheral factor in the ultra narrow lead process brings the stitch bond to be outside part of the lead in some parts of the die which in return courses large variations in stitch pull readings. Bonding parameters, wire diameter and capillary geometries are known to have a critical influence on the stitch width. Although bonding parameters and the WDare controllable they still have limitations which are related to the process specification and qualification constrains.

FAQs

Why does second-bond stitch width become crucial in ultra fine pitch packages?

As lead widths shrink, stitch width scales closer to the lead width, and even exceeding it leads to degradation in second-bond stitch pull results and reduced process stability.

What model is used to predict second-bond stitch width?

A JMP (ver. 7.0) model predicts second-bond stitch width based on capillary dimensions and wire diameter.

Which factors most strongly control second-bond stitch width?

The study’s key observation indicates wire diameter and tip size are the main contributors controlling second-bond stitch width.

Sep 5, 2026

Upload by Stanley