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Technical Pages
These pages have been produced to aid design engineers by helping them understand the
various properties and current process limitations and parameters for the various
technologies available through Copernica Ltd.
Please read the Disclaimer
notice before using the information provided.
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Properties of Substrate material
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Property
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Units
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96% Alumina
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99% Alumina
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Aluminum Nitride
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AlN Special
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| Density |
g/cc
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3.7
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3.9
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3.20-3.30
|
3.25
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| Colour |
-
|
White
|
White
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Grey - translucent |
White - translucent
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| Water absorbtion |
%
|
0
|
0
|
0
|
0
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| Elastic modulus |
GPa
|
300
|
370
|
320
|
-
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| Poisson's ratio |
-
|
0.21
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0.22
|
-
|
-
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| Flexural strength |
MPa
|
350-370
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350-390
|
360
|
-
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| Compressive strength |
MPa
|
2260
|
2600
|
-
|
-
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| Thermal conductivity |
W/mK
|
23-26
|
25-32
|
160 -180
|
260
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| CTE 25-1000 |
10-6/°C
|
8.2
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8.2
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3.8-4.4
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4.4
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| Specific heat |
j/kgK
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880
|
880
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738
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-
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| Thermal shock |
Delta(Tc)
|
250
|
200
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-
|
-
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| Dielectric strength |
ac kV/mm
|
8.3
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8.7
|
15
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15
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| Dielectric loss |
25°C @ 1MHz
|
0.0002
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0.0001
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0.0001
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0.0001-0.0003
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| Volume resistivity |
ohm.cm
25°C
500°C
1000°C
|
1014
4x109
1x106
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1014
2x1010
2x106
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1014
-
- |
1014
-
- |
Alumina is used for general purpose thick film hybrids circuits 96% is suitable for most cases,while 99% is used in high frequency, high resistance,
and high voltage circuits.
Aluminum Nitride substrates, because of high thermal conductivity (approximately six times that of Alumina), are most suited to power hybrid applications where rapid heat dissipation is a requirement. The material is well suited to die attach circuits as it exhibits a coefficient of thermal expansion closely matching that of Silicon. Aluminum Nitride requires special processing considerations and is a relatively expensive material. Copernica Ltd has developed unique techniques for processing Aluminum Nitride and considers itself the market leader in this field in the UK.
AlN Special is a material which exhibits higher thermal conductivity than standard Aluminum Nitride, approximately 220-230mW/K - which is higher than that of Beryllia, and does not have the associated health concerns.
Plated-through holes, unusual shapes, different thicknesses and sizes can be achieved on all the above materials depending on circuit applications. |
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Properties of Printed Resistors
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Property
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Min. |
Nom. |
Max |
Units |
| Value range |
0R01
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-
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20G
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ohms
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| Tolerance absolute |
0.1
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-
|
-
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%
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| Matching tolerance |
0.06
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-
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-
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%
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| Temperature coefficient of resistance (TCR) |
-50 to 50
|
100
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-
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ppm/°C
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| TCR tracking |
<10
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-
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-
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ppm/°C
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| Voltage handling (design dependant) |
-
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-
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40
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kV
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| Power handling (@70°C) |
-
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-
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0.15
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W/mm2
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| Printed thickness |
16
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18
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20
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microns
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| Power derating from nominal at 70°C to 0 at 120°C |
Thick film resistor circuits are a great advantage to the circuit designer. There is no need for tiresome re-calculations to normalize values to the E-type resistor series; simply specify the nominal value and tolerance and we can achieve it by laser trimming each individual resistor. This process is neither slow nor costly: many thousands of resistors can be trimmed accurately to value in one hour, keeping the cost down to that expected of a discrete device. Our quality control procedures ensure that all resistors are tested, unlike discrete devices which are prone to cracking, tomb-stoning, and dry joints etc., enhancing your product reliability.
We can design resistors to suit your needs, including position on the circuit, power requirements, voltage handling, and sensitivity to temperature change.
Adjust-On-Test resistors can be specified, so that parameters on a fully assembled hybrid can be normalized.
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Properties of Printed Conductors
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Property
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Min. |
Nom. |
Max |
Units |
| Track resistance range (dependent on material) |
2.5
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-
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10
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milliohms/square
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| Printed thickness - Gold (Au wire bondable) |
7
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9
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11
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microns
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| Printed thickness - Pd/Ag |
10
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12
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14
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microns
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| Temperature coefficient of track resistance (Pd/Ag) |
-
|
400
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-
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ppm/°C
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| Standard track width (all conductors) |
|
200
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-
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microns
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| Applications dependent track width |
150
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-
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-
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microns
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| Fine line track width (special process) |
50
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100
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-
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microns
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| Standard track separation (same layer) |
200
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250
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-
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microns
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| Fine-line track separation (same layer, special process) |
75
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100
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-
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microns
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| Adhesion strength to substrate (Pd/Ag unsoldered, 2x2mm, straight pull) |
40
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55
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-
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N
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| Adhesion strength to substrate (Pd/Ag soldered Ag/Pb/Sn, 2x2mm, 48
hrs @125°C, straight pull) |
-
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30
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-
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N
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All of above tests carried out on 96% Alumina.
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Materials Available:
Silver Palladium, Silver Platinum, Gold, Platinum Gold, Platinum.
Silver Palladium:
Silver palladium is used as a general purpose interconnect, exhibiting good solderability and relatively low track resistance. Several mixture ratios are available which are matched to appropriate applications.
Price is relatively low, compared with precious metals.
Silver Platinum:
Used as an alternative general purpose interconnect, having low track resistance and good solderability. Prices fluctuate with price of platinum. Can be used in budget applications for thermosonic wire bonding.
Gold:
Used in high reliability circuits, it exhibits excellent thermosonic bonding characteristics. Requires special soldering techniques. Prices fluctuate with world demand. Gold holds excellent printing definition making it ideal for fine-line applications.
Platinum Gold:
Often used as solderable termination on gold circuits, it exhibits good soldering characteristics, and is often used in high rel circuits.
Platinum:
Not commonly used as interconnect. Suitable alternatives are available, used mainly in sensor and high temp heater circuits. High cost.
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Printed Dielectric
There are many different types of dielectric material available to the thick film designer, each with its own properties and intended application. Dielectric material is used commonly on cross-over, multi-layer, and capacitor applications, but does have many other uses.
Dielectric is used as an insulation layer for cross-over applications (where one printed track crosses over another). Multilayer applications use large areas of tracking layered over each other separated by dielectric layers, connected through by via holes in the dielectric. Dielectric materials have a known dielectric constant. The fired thickness of the deposition can be controlled, hence it is possible to print thick film capacitors by separating two conductive plates with
dielectric.
Although the capacitance tends to be relatively low compared to a chip capacitor (typically tens of pF), the voltage breakdown can be very high. Copernica Ltd produces a range of capacitors that can withstand voltage between the plates in excess of 4kV.
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Property
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Value
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Units
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| Typical fired thickness (2 to 3 layers) |
35-60
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microns
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| Dielectric constant K (typical) @1kHz |
7-10
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-
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| Dielectric constant K (typical) @1MHz |
6-8
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-
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| Insulation resistance @100V DC |
1011
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ohms
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| Breakdown voltage depending on material used. ( air @25°C) |
600 to 1000 /50micron
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V
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| Minimum via definition (depending on material used) |
175x175
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microns |
Fine-Line Printing
Printed conductors which are less than 150 microns wide with a similar track separation are generally considered fine-line in printed thick film parlance. However Copernica Ltd has responded to market trends and is currently at the forefront of thick film printing technology, developing ever finer track definition. Currently Copernica Ltd has currently developed increased definition to 50 microns - using a European Community assisted technological advancement programme.
Applications include high frequency circuits, high density interconnect for integrated packages and thick film inductors.
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Adjust-On-Test Sub-assemblies
Traditionally a number of trimming potentiometers are included in the circuit. However these suffer from long term drift, noise problems, and can be difficult
and expensive to set. A much more reliable way of achieving the desired effect is to design and assemble the circuit using thick film hybrid technology.
With a hybrid design, printed thick film resistor tracks are incorporated into the circuit and these can be laser trimmed after assembly to produce specified
circuit outputs to a high degree of precision.
At Copernica Ltd, an iterative technique, known as 'adjust-on-test' (AOT), is employed whereby the newly assembled circuit is tested with sample inputs.
Its output responses are measured and the resistors are trimmed accordingly so that the circuit is individually tuned to the required performance level.
The adjust-on-test procedure trims out the off sets and ac performance variations of the associated components, and produces a circuit sub-assembly which performs to within tight tolerances. The value of the output is controlled by the adjust-on-test procedure and is unaffected by relatively wide tolerances on the components.
However, a major advantage to be gained from using adjusted on test assemblies is that once the final trim levels have been set, the circuits are extremely
reliable and stable. The trimmed resistors are not subject to long term 'drift', as are trimming potentiometers, and they are easily protected from harsh operating environments by sealing them with an epoxy resin coating. Moreover, the circuits cannot be altered, inadvertently or otherwise, by the end users customer.
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TCR Calculations
Temperature coefficient of resistance is calculated using the formula
below:
TCR = (((Rc - Rh)/Rc)/dT) *1000000
expressed in ppm/°C
Rc = cold resistance
Rh = hot resistance
dT = change in temperature
Generally expressed as hot TCR or cold TCR. Cold TCR is measured between
-50°C and +25°C, hot TCR is measured between +25°C and +75°C.
All TCR specifications given by Copernica Ltd are expressed as hot
TCRs.
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VCR Calculations
Voltage coefficient of resistance for any given resistor is calculated
using the formula below:
VCR = (((Rl - Rh)/Rl)/dV) *1000000
expressed in ppm/V
Rl = resistance measure at low voltage
Rh = resistance measured at higher voltage
dV = change in voltage
VCR specifications given by Copernica Ltd are expressed from measurements
taken between 100V and 200V DC, provided that the resistor in question
is capable of withstanding the applied voltage. If not, then an appropriate
lower voltage difference is used.
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DISCLAIMER:
Reasonable care has been taken in the preparation of this information,
but Copernica Ltd EXTENDS NO WARRANTIES, MAKES NO REPRESENTATIONS
AND ASSUMES NO RESPONSIBILITY AS TO ACCURACY OR SUITABILITY OF THIS INFORMATION
FOR ANY PURCHASER’S OR USER’S USE OR FOR ANY CONSEQUENCE OF THERE USE.
COPERNICA LTD DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR WARRANTY
OF FITNESS FOR ANY PARTICULAR USE. All statements, technical information
and recommendations contained herein are based on Seller’s or Manufacturer’s
test and the test of others, and are believed to be accurate, but no guarantee
of accuracy is made. Judgement as to the suitability of information herein
or the user’s purposes are necessarily the user’s responsibility. Users
shall determine the suitability of the products for their own intended
application.
Users assume all risk of
use or handling whether or not in accordance with any statements or recommendation
of the seller or manufacturer, Liability, if any, is and shall be limited
to the replacement of such quantity of material proved not to conform to
specifications as set out in product specification. Statements concerning
the possible use of these products are not intended as recommendation to
use these products in infringement of any patent. No guarantee is made
that any use of the products does not infringe third-party intellectual
property or patent rights anywhere in the world.
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