Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-11-06
2001-02-13
Crispino, Richard (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S378000, C156S379000
Reexamination Certificate
active
06187121
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to die-bonding equipment and methods for detecting whether an adhesive such as Ag-epoxy is properly dotted on a die pad of a lead frame or a substrate, enabling timely replacement of adhesive tubes and preventing poor bonding of a semiconductor chip to the die pad.
2. Description of the Related Art
Generally, an assembly process of semiconductor packages includes: dicing of a wafer including a number of semiconductor chips into individual semiconductor chips; bonding of each semiconductor chip on a die pad of a lead frame using an adhesive; wire-bonding to connect the bonding pads of the semiconductor chip to inner leads of the lead frame; encapsulation of the semiconductor chip, the wire and the inner leads with a molding compound to protect the semiconductor chip from the external environment; singulation of each individual package and forming outer leads of the lead frame; and marking of a trademark and a product serial number on the package.
In the die-bonding process, the lead frame is placed at a predetermined position by a transferring unit, and an adhesive is dotted on the die pad of the lead frame by a dispenser in the die-bonding equipment. Then, a bonding-head picks up a semiconductor chip and attaches the backside of the semiconductor chip to the die pad. The final step of the die-bonding process is curing of the adhesive.
Ag-epoxy adhesive is commonly used as an adhesive between a die pad and a semiconductor chip. In the die-bonding equipment, Ag-epoxy adhesive contained in a tube is loaded in a dispenser. When the tube is empty or nearly empty, an operator of the apparatus replaces the tube with a new tube.
To select when to replace the tube, the operator loads a new adhesive tube, and sets a controlling unit with an expected number of dotting operation from the tube. When operating, the equipment counts actual adhesive dotting, and when the count is the same as the set number, the control unit alerts operator to inform the operator that the presently used tube is running out of the adhesive and needs to be replaced with a new one. Thus, the operator replaces the adhesive tube according to the number of dottings, not according to the state of adhesive dotting on the die pad. Generally, the operator changes the expected number of dottings according to the size of semiconductor chips because larger chips need more adhesive for die bonding. However, the expected number set by the operator can be incorrect due to a miscalculation of the chip size and adhesive use at an expected rate, or human error in setting the expected number. The set number being incorrect can result in waste of adhesive if tubes are changed too often or improper bonding if tubes are changed too infrequently.
SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, a die-bonding equipment detects the state of adhesive dotted on a die pad of a lead frame or a substrate using a camera and determines when the adhesive tube being used should be replaced with a new one.
One embodiment of die-bonding equipment according to the present invention includes: a loading unit for loading a lead frame or a substrate; a dispenser for dotting an adhesive on a die pad of the lead frame or the substrate; an adhesive detecting unit; a bonding head unit for picking up a semiconductor chip and attaching the semiconductor chip to the die pad; and an unloading unit for unloading the lead frame or the substrate with the semiconductor chip attached thereto.
The adhesive detecting unit includes: an overlapped pattern forming unit for overlap-photographing a pattern of adhesive dots on the die pad of the lead frame or the substrate and a standard pattern for the dots; a determining unit for determining whether the adhesive is properly dotted; and a controlling unit for displaying the result on an output unit and/or generating an alarm signal to inform the operator that the adhesive is not properly dotted.
A first embodiment of the overlapped pattern forming unit includes: a body; a semitransparent member; a standard pattern forming unit; a camera unit for photographing a dotted adhesive pattern and the standard pattern projected on the semitransparent member; and a light-emitting unit for providing light for camera.
The components of the overlapped pattern forming unit can be placed inside the unit in various ways for proper overlap-photographing of the dotted adhesive pattern and the standard adhesive pattern. Additional components can also be included in the overlapped pattern forming unit to accomplish the same purpose.
The present invention also provides a method for detecting adhesive dotted on a die pad of a lead frame or a substrate. The method comprises the steps of: overlap-photographing of a standard pattern and an adhesive pattern dotted on the die pad; reading and inputting of the standard pattern; subsequent reading and inputting of the dotted adhesive pattern; evaluating the degree of overlap between the standard pattern and the dotted adhesive pattern; and generating an alarm signal when the evaluation shows that the adhesive is not properly dotted.
Therefore, the present invention can enable a timely notice of adhesive tube replacement and prevent poor die bonding caused by an improper adhesive dispensing.
REFERENCES:
patent: 3909602 (1975-09-01), Micka
patent: 5908150 (1999-06-01), Miura
Ha Yong-dae
Hong Sung-bok
Hwang Young-gon
Lee Yong-choul
Crispino Richard
Koch, III George R
Millers David T.
Samsung Electronics Co,. Ltd.
Skjerven Morrill & MacPherson
LandOfFree
Die-bonding equipment and a method for detecting residual... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Die-bonding equipment and a method for detecting residual..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Die-bonding equipment and a method for detecting residual... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2582583