Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-01-05
2001-02-06
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S593000, C029S740000, C029S840000, C029S411000, C029S412000
Reexamination Certificate
active
06182357
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to printed circuit boards. More particularly, the present invention relates to a method and apparatus for manufacturing printed circuit boards. Still more particularly, the present invention relates to a new, cost effective manufacturing technique for cutting (“dicing”) a circuit board substrate that also permits an increase in the density of components on the board.
2. Background of the Invention
Many types of electronic equipment include printed circuit boards. A printed circuit board (“PCB”) generally includes a substantially rigid substrate constructed from ceramic or other suitable material, semiconductors and other types of interconnected electronic components attached to the substrate. PCB's are widely used in a wide variety of electronic equipment such as computers, calculators, telephones, watches, pacemakers and cellular telephones.
Usually it is desirable, and in many instances imperative, that devices, such as laptop computers, implantable medical devices and cellular telephones, be as small as possible. Accordingly, the components used to construct such devices, including the PCB, must be miniaturized as much as possible. It is also desirable to reduce manufacturing cost whenever and wherever possible. Thus, designers and manufacturers of PCB's continuously strive to provide smaller, less expensive circuit boards that lower the cost of the finished product. The present invention generally relates to a method and apparatus for making PCB's smaller and less costly than previously possible. To fully appreciate the benefits of the invention, a conventional technique for manufacturing a typical PCB will now be described.
Referring first to
FIG. 1
, the layout of a conventional PCB
20
includes a substrate
22
and one or more electronic components
32
mounted on one or two sides of the substrate
22
. The components
32
are mounted in a central circuit area
28
of the substrate
22
. Usually, in the initial stages of manufacturing, the PCB
20
includes waste edges
24
(also referred to as “wings”) on either side of the central circuit area
28
. The waste edges
24
result from the fact that the raw substrate
22
typically is manufactured in a predefined width W, but the central circuit area
28
does not require the full width of the substrate
22
. Also, one or more conductive test pads
26
, electrically connected to various components
32
, are included in central circuit area
28
for testing purposes as explained below.
A typical PCB manufacturing process will now be explained. As shown in
FIG. 2
, the substrate
22
is manufactured in step
40
and prepared for use to assemble the PCB. Step
40
includes creating all of the conductive traces on and within the substrate
22
for interconnecting the components that will be mounted on the substrate in step
50
. In step
46
the waste edges
24
are removed using a conventional PCB chuck saw. The saw includes an electrically-controlled chuck table
34
as shown in
FIG. 3
which has a substantially flat workpiece fixture
36
on which the PCB is placed. A precision circular saw (not shown) then is used to cut the substrate along lines
30
(
FIG. 1
) separating waste edges
24
from central circuit area
28
. The table fixture
34
uses vacuum suction to hold the PCB
20
in place while the cutting step is performed. The vacuum is supplied from a vacuum pump (not shown) through slots or holes
38
in the workpiece fixture
36
. As can be seen in
FIG. 3
, the workpiece fixture
36
of the chuck table
34
is flat to permit adequate suction for holding the PCB
20
in place. To use this type of chuck table, the PCB
20
must also be flat during cutting step
46
, and thus the electrical components to be mounted on the substrate
22
typically are not mounted until after the waste edges are cut off.
Although it is desirable to cut through the substrate
22
in step
46
, for obvious reasons it is not desirable to cut the top surface of the workpiece fixture
36
holding the PCB
20
and place. To avoid cutting the workpiece fixture
36
, an adhesive polymer tape is applied to the bottom surface of the PCB
20
in step
42
. The polymer tape acts as a spacer and typically is 0.003-0.005 inches thick. Further, the substrate
22
and polymer tape are baked in step
44
to activate the adhesive in the tape.
It is important to maintain the PCB
20
as clean as possible and to protect it from damage during manufacturing. To avoid damaging the PCB once the waste edges
24
are removed, the PCB is placed in a protective carrier (carrier not shown) in step
48
. The carrier may be constructed from plastic or other suitable type of material and is generally a rigid structure whose purpose is to protect PCB during the remainder of the manufacturing process. In step
50
, the components are mounted on the substrate
22
using conventional surface mount technology (SMT) or other suitable manufacturing technology. In step
52
the completed PCB is tested to insure that it functions as intended. The testing process typically includes one or more electrical tests in which the circuit on the PCB
20
is activated and the signals on the test pads
26
are monitored for proper signal level and timing. If the PCB passes testing, it is then assembled into the electrical equipment or sold as a separate component.
Because of the relatively high complexity of the conventional manufacturing method of
FIG. 1
, the potential for errors to occur is significant. Each step of a manufacturing process has risks for errors to occur. A process with many steps, therefore, has a greater chance for errors to occur than a process with fewer steps. Accordingly, it would be desirable to have a PCB manufacturing process with fewer steps than the conventional process of FIG.
2
.
Additionally, the cost involved with the conventional manufacturing process shown in
FIG. 2
is substantial. The cost includes:
The carriers used to hold and protect the PCB after the waste edges
24
are removed.
Cleaning and recycling the carriers for use with subsequent PCB's.
The polymer tape applied to the bottom surface of the substrate
22
.
The oven needed to activate the polymer tape's adhesive.
These costs and others drive up the price of the finished PCB. It is desirable to minimize manufacturing costs as much as possible.
As noted above, it is also desirable to miniaturize many PCB's to the fullest extent possible. Miniaturization involves two related aspects: (1) implementing a circuit on a PCB so as to take up as little surface area as possible, and (2) manufacturing a PCB to include as many components as possible in a given space. In either case, the “density” of the circuit is increased. The goal of PCB miniaturization generally involves includes the component density.
It would be highly desirable to have a less costly PCB manufacturing process. It would also be desirable to have a PCB manufacturing process for making PCB's with higher component density. Such PCB's would result in lower priced, smaller equipment that incorporate such PCB's.
BRIEF SUMMARY OF THE INVENTION
The problems noted above are solved in large part by a manufacturing method and apparatus for dicing printed circuit boards that permits PCB's to be cut without the need for a carrier. By avoiding the necessity for a carrier, the cost of the carrier is avoided as well as the cost of cleaning and otherwise recycling the carrier for subsequent use. Also, the method includes relatively fewer steps and thus has less potential for errors to occur. Further, the disclosed method and apparatus permits PCB's to be cut without the need for tape to be applied to the bottom surface of the substrate to act as a spacer. Thus, the cost of the tape is also avoided as well as the oven that is typically necessary to heat tape's adhesive.
The preferred manufacturing method generally comprises forming a raw substrate to include conductive traces, mounting c
Chen Philip H.
Gadd Timothy M.
Munson John C.
Arbes Carl J.
Intermedics Inc.
Schwegman Lundberg Woessner & Kluth P.A.
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