Thermal measuring and testing – Leak or flaw detection – With heating or cooling of specimen for test
Reexamination Certificate
2000-03-09
2002-08-06
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Leak or flaw detection
With heating or cooling of specimen for test
Reexamination Certificate
active
06428202
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for inspecting the connection state of an electronic part and the substrate, and an apparatus for the same.
2. Description of the Prior Art
As known inspection methods according to the prior for the state of connection between an electronic part and a substrate, an electrical continuity inspection, a visual inspection and an X-ray inspection are existing.
The Japanese Published Patent No. 38501/1995 (published on Apr. 26, 1995 in Japan) discloses a technique whereby the part to be checked is irradiated with laser light and its connection state is judged according to its temperature rise. This technique will be described below as an example of the prior art.
FIG. 9
is a front cross-sectional view of a connection state inspecting apparatus for an electronic part and a substrate according to the conventional example.
The conventional apparatus shown in
FIG. 9
consists of a laser light source
109
, a lens
111
, a detector
113
and a quality judgement unit
114
.
A surface-mounted part
120
, which is to be checked by this apparatus, consists of a package
126
, pads
125
formed over the top surface of this package
126
, and through holes
127
electrically connected to these pads
125
and penetrating the package
126
downward. Each of the through holes
127
is connected to the upper surface of a substrate
107
by solder connecting portions
104
.
In this apparatus according to the prior art, the pads
125
are irradiated with a laser beam
110
, radiated infrared rays
112
from the pads
125
are received to measure the increment of a temperature character value Va. This increment is compared with a preset increment to evaluate the connection state of the solder connecting portions
104
.
This conventional apparatus is characterized in that the pads
125
and the through holes
127
are structurally added afterward to the package
126
to heat the solder connecting portions
104
which are not exposed on the surface and accordingly cannot be irradiated with the laser beam
110
. The solder connecting portions
104
are thermally coupled to the pads
125
by the through holes
127
.
However, this conventional apparatus has the following problems.
First, the need to form the pads
125
and the through holes
127
within the package
126
for the sole purpose of inspecting the connection state significantly limits the arrangement of wiring routes in the package
126
.
Second, a step to bore many through holes
127
into the package
126
, a step to fill these through holes
127
with electroconductive material and a step to form a pad
125
over the top of each through hole
127
are indispensable merely for inspecting the connection state. This results in a substantial increase in the number of required steps in the manufacturing process and a corresponding increase in production cost.
Third, the low intensity of the radiated infrared rays
112
emitted by the temperature rise of the pads
125
brings down the accuracy of quality of judgement.
Thus, a plating layer of metal, such as nickel or gold, is usually formed over the surface of each of the pads
125
. These metals have the extremely low infrared emission character of any such metal invites a very low intensity of the radiated infrared rays
112
emitted from the pads
125
themselves even if the temperature of the pads
125
rises.
Fourth, a high intensity of unnecessary infrared rays scattered over the surfaces of the pads
125
brings down the accuracy of quality judgement.
Because gold has very high infrared reflection character, the reflected light on the pads
125
is incident into the detector
113
as noise components.
SUMMARY OF THE INVENTION
In view of these problems, a first object of the present invention is to provide a method for inspecting the connection state of an electronic part and a substrate and an apparatus for the same which permits judgement of the quality of the connection state at high accuracy without needing structural addition of through holes and pads for use in connection state inspection.
A second object of the present invention is to provide a method for inspecting the connection state of an electronic part and a substrate and an apparatus for the same which permits judgement of the quality of the connection state at high accuracy even where the terminals for electrical inspection of the part to be inspected are gold-plated or otherwise and accordingly poor in infrared emission character.
A method for inspecting a connection state of an electronic part and a substrate, the electronic part having a terminal for electrical inspection electrically connected to a solder connecting portion, and being connected to a surface of the substrate by the solder connecting portion, has the steps of: heating a first specific position on the electronic part, measuring a temperature rise of a second specific position thermally coupled to the first specific position, and judging the quality of the connection state of the solder connecting portion by comparing the measured temperature rise and a reference temperature rise.
An apparatus for inspecting a connection state of an electronic part and a substrate, the electronic part having a terminal for electrical inspection electrically connected to solder connecting portion, and being connected to a surface of the substrate by the solder connecting portion, has: a heating unit for heating a first specific position on the electronic part, a thermometer for measuring a temperature rise of a second specific position thermally coupled to the first specific position, and a quality judgement unit for judging the connection state of the solder connecting portion by comparing the measured temperature rise with a reference temperature rise.
By the adoption of such the method and the apparatus, the invention makes possible to judge the connection state by using the terminals for electrical inspection, which are previously formed thereon.
Even where the infrared emission character of the terminals is low, the quality of the connection state can be judged on the basis of the temperature rise on specific positions thermally connected to these terminals.
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patent: 5407275 (1995-04-01), Long
patent: 5493594 (1996-02-01), Hamada et al.
patent: 5971608 (1999-10-01), Koizumi
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patent: 6028358 (2000-02-01), Suzuki
patent: 2164147 (1986-03-01), None
patent: 0243574 (1985-12-01), None
patent: 06132586 (1994-05-01), None
D.Schumacher. Measuring Microbond Integrity With an Infrared Microradiometer. 27th National Fall Conference of the American Society for Non-Destructive Testing. Oct., 1967.
Mitsuhashi Hideo
Ookawa Katsuhisa
Gutierrez Diego
NEC Corporation
Verbitsky Gail
Whitham Curtis & Christofferson, PC
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