Laminates
Download our FREE Microwave Laminates Comparison Chart. Makes a great reference tool for engineers.
Laminates are considered the
foundational substrate on to which the electrical circuits and connections
are imaged, plated, and etched. Laminate normally consists of a
dielectric layer sandwiched between 1 or 2 copper clad layers.
Typically the dielectric thickness is referred to as the core thickness
(without copper) and the overall thickness is with the copper layer(s)
included. 1 ounce copper signifies that one ounce of copper is used to
cover 1 square foot of dielectric. Copper thicknesses are converted to
mils below:
| COPPER OUNCES | THICKNESS (MILS) |
| 1/2 Oz. | 0.7 |
| 1 Oz. | 1.4 |
| 2 Oz. | 2.8 |
| 3 Oz | 4.2 |
| 4 Oz | 5.6 |
| 5 Oz. | 7.0 |
When specifying laminates, there are a couple of different ways to designate:
|
TYPE |
DIELECTRIC THICKNESS |
COPPER |
COMMENTS |
| IPC-4101/xx | 0.059 core | C1/C1 | xx - number assigns actual laminate type per IPC-4101 |
| FR4 | 0.059 core | C1/1 | FR4 - is a standard laminate, C1/1 designates copper 1oz both sides |
| FR4 | 0.062 OA | C1/1 | .062 is specified as an overall laminate thickness including copper |
| FR4 | 0.062 OA | 2 oz finished (2 sides) | copper thickness specified as after plating |
The following chart specifies laminate thickness tolerances according to IPC Specifications. (Note: These tolerances do not apply to RF/Microwave laminates):
| THICKNESS | CLASS A | CLASS B | CLASS C |
| 0.008-0.039" | +/- 0.008" | +/- 0.004" | +/- 0.002" |
| 0.047-0.063" | +/- 0.012" | +/- 0.008" | +/- 0.004" |
| 0.079-0.094 | +/- 0.016" | +/- 0.010" | +/- 0.006" |
| 0.125-above | +/- 15% of nominal | +/- 10% of nominal | +/- 5% of nominal |
Additional information on the various laminate types is available on separate pages listed below.
IPC-4101 Reference
Chart
This table is taken
from IPC-4101 Specification for Base Materials for Rigid and Multilayer
Printed Boards. The U.S. Department of Defense has adopted this
specification upon cancellation of MIL-S-13949. Although the
specification itself includes additional information, the table included will
help identify certain laminates, cross-reference MIL and NEMA P/Ns and briefly
define various operating properties. If more
information is required, you should contact the IPC
http://www.ipc.org and request a copy of
the specification.
Standard FR4 Laminate
These are the
most commonly used family of laminates and are considered the standard for
most printed circuit applications.
High Temperature
Laminates
Microwave Laminates
Comparison Chart |
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Circuits Inc.
Through the use
of various resin systems, high temperature PCB laminates are now
becoming more prevalent today's applications. Some multi-functional
epoxies are getting close to the performance characteristics of polyimide.
A comprehensive comparison chart to help
engineers find the right RF laminate for their particular application.
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