U.S. patent application number 10/468688 was filed with the patent office on 2004-04-15 for method and device for applying a solder to a substrate.
Invention is credited to Azdasht, Ghassem, Titerle, Lars.
Application Number | 20040069758 10/468688 |
Document ID | / |
Family ID | 7690686 |
Filed Date | 2004-04-15 |
United States Patent
Application |
20040069758 |
Kind Code |
A1 |
Azdasht, Ghassem ; et
al. |
April 15, 2004 |
Method and device for applying a solder to a substrate
Abstract
The invention is a method for applying a solder to a substrate
by positioning it in its solid physical condition, melting it and
then impacting it against a substrate by means of compressed gas.
The device for applying a solder (7) to a substrate (10, 11)
comprises a holder (1) having a capillary bore (2) whose diameter,
at the substrate end (3), has a contraction (4) whose diameter (D2)
is smaller than the diameter (D3) of the solder globule (7).
Inventors: |
Azdasht, Ghassem; (Berlin,
DE) ; Titerle, Lars; (Berlin, DE) |
Correspondence
Address: |
Dougherty Clements & Hofer
Suite 300
1901 Roxborough Road
Charlotte
NC
28211
US
|
Family ID: |
7690686 |
Appl. No.: |
10/468688 |
Filed: |
August 20, 2003 |
PCT Filed: |
June 26, 2002 |
PCT NO: |
PCT/EP02/07034 |
Current U.S.
Class: |
219/121.85 |
Current CPC
Class: |
H05K 2203/074 20130101;
H05K 3/3478 20130101; B23K 3/0607 20130101; H05K 2203/041 20130101;
H05K 2203/086 20130101; B23K 3/0623 20130101; H05K 2203/0195
20130101 |
Class at
Publication: |
219/121.85 |
International
Class: |
B23K 001/005 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2001 |
DE |
101 32 567.3 |
Claims
What is claimed is:
1. A process for applying solder on a substrate comprising
providing solder in a sold aggregate state, positioning solder
relative to the substrate, providing an energy source, and melting
the solder by activating the supply of energy, characterized in
that the positioning is realized by spacing solder a predetermined
distance from the substrate, and impacting the solder against the
substrate by action of a compressed gas after melting of the
solder.
2. A process according to claim 1, characterized in that the
melting is performed through laser energy.
3. A device for applying solder onto a substrate comprising a
holder having a capillary therein in which a solder ball can be
positioned relative to the substrate, the end of the capillary (2)
nearer the substrate having a tapered section (4), whose smallest
diameter (D2) is smaller than the diameter (D3) of the solder ball
(7).
4. A device according to claim 3, characterized in that the tapered
section (4) is conical from a larger diameter (D1) of the capillary
(2) to a smaller discharge diameter (D2).
5. A device according to claim 3, characterized in that a
compressed gas source (9) is connected to the capillary (2).
6. A device according to claim 5, characterized in that means is
provided for the compressed gas to be activated in pulses.
7. A device according to claim 5, characterized in that the
compressed gas is an inert or protective gas.
Description
[0001] The invention concerns a process and a device for applying
solder onto a substrate including providing solder in a sold
aggregate state, positioning solder relative to the substrate,
providing an energy source, and melting the solder by activating
the supply of energy,
[0002] Such processes and devices are known from German patents DE
43 20 055 A1, DE 42 00 492 C2, and DE 195 33 171 A1. These
processes and devices have a holder with a capillary. The holder is
placed with its tip near the solder point, and then a solder ball
is fed through the capillary and the solder ball contacts the
solder point. The solder ball is then melted through the capillary.
The melting is preferably performed using laser energy.
[0003] To transport the solder ball within the capillary, DE 43 20
055 A1 proposes to arrange a movable optical fiber within the
capillary, so that the optical fiber acts as a ram for moving the
solder ball and is simultaneously also used for feeding laser
energy.
[0004] DE 195 33 171 A1 instead proposes to transport the solder
ball by the force of gravity, vibration, particularly ultrasound,
and an air flow. In addition, for DE 195 44 929 A1, solder balls
are transported by the pressure of a protective gas.
[0005] In the prior art, however, the solder ball always contacts
the substrate or the surface to be wetted with the solder material
at the moment of melting. This requires that the tip of the holder
must be positioned very close against the substrate, wherein on the
one hand, the solder ball is still held in the capillary, and on
the other hand, however, the solder ball is already in contact with
the substrate. Because the solder balls in many cases have a
diameter of a few microns, this requires extremely precise
positioning of the holder and there is the risk that the holder
will collide with parts on the substrate during positioning.
[0006] The problem of the invention is to improve upon the known
process and device in such a way that a sufficiently precise
placement of the solder material on the substrate is achieved while
simultaneously reducing the positioning accuracy requirements of
the holder.
[0007] This problem is solved by the features given in claims 1 and
3. Advantageous configurations and refinements of the invention can
be found in the subordinate claims.
[0008] The fundamental principle of the invention is to position
the solder in a solid aggregate state and to hold it at a distance
from the substrate. Then, through the supply of energy, the solder
is melted and finally pushed against the substrate by a compressed
gas. Regarding the device, the capillary is tapered near the tip so
that its diameter is smaller than the diameter of the solder
ball.
[0009] Thus, the ball falls down to the tapered section and is held
there. The holder is then positioned at a sufficient distance above
the substrate. Then the ball is melted, preferably by laser light,
and pushed against the surface to be soldered by compressed gas.
The distance between the tip of the holder and the substrate is
therefore no longer critical, so that in terms of this distance,
the positioning accuracy requirements are reduced. simultaneous-ly,
the positioning accuracy requirements in the plane of the substrate
(X/Y plane) are also reduced. In the prior art, the ball could move
in the X/Y plane at the solder position if the lower edge of the
capillary from the substrate had a greater distance than the radius
of the solder ball. In contrast, such a motion is not possible with
the invention and the center of the capillary also corresponds to
the center of the solder ball.
[0010] Another advantage is that all of the laser energy is
definitely incident on the solder ball and cannot pass the solder
ball.
[0011] The compressed gas for pushing the melted solder material is
preferably a protective gas, e.g., an inert gas.
[0012] The solder can be not only solder tin, but also other
meltable materials, e.g., also plastics.
[0013] In the following, the invention is described in more detail
with reference to an embodiment in connection with the drawing.
Shown are:
[0014] FIG. 1, a schematic diagram of the device before melting of
the solder ball; and
[0015] FIG. 2, a diagram similar to FIG. 1, but after the melting
of the solder ball.
[0016] FIG. 1 shows schematically a holder 1 with a capillary 2,
which has a first diameter D1. At the lower end 3 of the capillary
2 there is a conical tapered section, which runs to a conical point
starting from the first diameter D1 down to a second diameter D2
and thus forms a tapered outlet 5 at the tip 6 of the holder. The
diameter D1 and D2 are set relative to the diameter D3 of the
solder ball 7 such that the first diameter D1 of the capillary 2 is
larger than the diameter of the solder ball and the second diameter
D2 at the outlet 5 of the tapered section is smaller than the
diameter D3 of the solder ball. In this way, the solder ball is
easily guided from above in the direction of arrow 8 to the tapered
section 4, even just by the force of gravity. The solder ball is
held at the tapered section 4 and it partially seals the capillary
from the top. In an optimum arrangement, there is absolutely no
gap, through from which light, particularly laser light, could exit
the capillary, when there is a solder ball 7 in the tapered section
4.
[0017] The feeding of a solder ball to the capillary is performed
in a known way (cf., e.g., DE 195 44 929 A1 or DE 195 33 171 A1) by
a device, which is designated in general by the reference numeral
9, for gathering single balls, for feeding, for control, and for
generating laser light.
[0018] As illustrated in FIG. 1, the holder with the solder ball
still held at the tip of the holder is positioned above a substrate
10, e.g., in the region of a conductive trace 11, at a certain
vertical distance from the substrate or the conductive trace 11. In
this position, there is no contact between the solder ball 7 and
the conductive trace 11. Then the solder ball 7 is melted by laser
light or some other energy source and pushed out of the capillary
by compressed gas and "accelerated", so that it wets the surface to
be wetted, e.g., the conductive trace 11, as a "bumper" 12, as
illustrated in FIG. 2.
[0019] Because the melted solder ball is accelerated by compressed
gas, which is preferably activated in pulses, and thus strikes the
substrate with some velocity, the wetting is also improved, because
the melted solder material also penetrates into small surface
irregularities, gaps, or the like in the substrate or the
conductive trace due to the impact pulse.
* * * * *