The present invention relates to a method of detaching an article fixed through a pressure sensitive adhesive double coated sheet and a detacher apparatus therefor.
For example, the wafer of a semiconductor such as silicon is produced in the form of a disc of large diameter. A circuit pattern is formed on a surface of the semiconductor wafer, and the back thereof is ground.
In recent years, there is a demand for the reduction of the thickness of semiconductor chips for IC cards and the like. It is now demanded to reduce the thickness of semiconductor chips produced from the semiconductor wafer, which has been 300-400 xcexcm, to about 100-50 xcexcm. Generally, a pressure sensitive adhesive sheet, which is produced by coating a soft base with a pressure sensitive adhesive, is used for fixing the semiconductor wafer to, for example, a table while protecting the surface of the semiconductor wafer provided with a circuit pattern.
In the detaching of an extremely thin semiconductor wafer from the soft pressure sensitive adhesive sheet, the semiconductor wafer may be cracked during the detaching operation by residual stress resulting from accumulation of the tension applied at the time of sticking. For coping with this problem, the inventors proposed a new pressure sensitive adhesive double coated sheet having pressure sensitive adhesive layers superimposed on a heat shrinkable base, which enabled easily detaching articles by first exposing it to ultraviolet light and thereafter heating the same. In the use of this pressure sensitive adhesive double coated sheet, the first exposure to ultraviolet light lowered the adhesive strength of the pressure sensitive adhesive layers, and the subsequent heating induced shrinking and deformation of the heat shrinkable base to thereby enable easily detaching the articles from the pressure sensitive adhesive sheet.
However, the use of this heat shrink pressure sensitive adhesive sheet has caused the following problem. That is, in the use of the heat shrink pressure sensitive adhesive sheet, shrinking begins at part heated so as to have its temperature raised. When the article is one of small area, the whole is heated and detached within a short period of time, irrespective of the location of heating. Thus, with respect to articles of small area, cracking has been rare. However, when an article of large area is heated at its center, detaching begins at a part near a heating source, with the result that a substantial tensile force is exerted between there and an outer part not yet satisfactorily heated. The tensile force is likely to cause cracking of articles.
In these circumstances, it is the object of an present invention to provide a method of detaching an article fixed through a pressure sensitive adhesive double coated sheet and a detacher apparatus therefor, which enables efficiently detaching articles, such as extremely thin wafers, without cracking thereof by the use of a heat shrink pressure sensitive adhesive double coated sheet.
For attaining the above object, according to the present invention, there is provided a method of detaching an article from a laminate unit, the laminate unit comprising a support plate and, fixed thereto, the article, the fixing effected through a pressure sensitive adhesive double coated sheet deformable by heating to thereby exert a peeling effect,
which method comprises:
heating at least one outer part of the laminate unit so that at least part of an outer region of the laminate unit is initially heated up, with other regions heated up later, and
detaching the article from the pressure sensitive adhesive double coated sheet in a direction from the outer region toward the other regions.
In this constitution, at least one outer part of the laminate unit is initially heated up and thereafter the heated up part can be slowly extended to other regions. Thus, the article can be easily detached from the initially heated up part of the pressure sensitive adhesive double coated sheet.
In the present invention, preferably, the initially heated up outer region of the laminate unit is a peripheral region extending in approximately a doughnut shape from a center of the laminate unit.
In this constitution, the peripheral region is detached initially and the inner region can be detached later. Thus, the article, even if extremely thin, can be easily detached, without cracking thereof, from the pressure sensitive adhesive double coated sheet.
Further, according to the present invention, there is provided a detacher apparatus for detaching an article from a laminate unit, the laminate unit comprising a support plate and, fixed thereto, the article, the fixing effected through a pressure sensitive adhesive double coated sheet deformable by heating to thereby exert a peeling effect,
which apparatus comprises heat-up means, the heat-up means including a first heat-up member capable of heating up at least one outer part of the laminate unit and a second heat-up member capable of heating up other parts of the laminate unit later than the first heat-up member.
This apparatus enables easily detaching the article, even if extremely thin, from the pressure sensitive adhesive double coated sheet without cracking of the article.