2.0 Conductors:
2.1 PdAg and Au line widths of 0.005"
are standard in our process. Line widths down to 0.003"
in gold are acceptable in APTA’s print process. Line widths
and spaces less than 0.003" are available with APTA’s
gold etch process. Gold etch may be used when extremely
precise line edges are required.
2.2 Conductor spaces down to 0.005"
are standard. 0.003" spacing may be used sparingly. 0.004"
Au spaces are standard.
2.3 A 0.010" wide area around the
perimeter of the part should be kept free of printed circuit
elements. This includes conductors, resistors, and overglazes,
but does not need to include dielectrics. This area is
to allow for laser scribing. The rule may be violated
if incidental damage to the conductor or other circuit
element by the laser scribe is acceptable.
2.4 Through holes are 0.007" in diameter.
The preferred land pad size is 0.015", either square or
round. A 0.012" land pad is acceptable.
2.5
If gold runs are being terminated to solder pads requiring
SnPb solder, the termination area must be out of the solder
area with a minimum overlap of 0.005", and be covered
by glaze with no less than 0.005" between solder pad side
of termination and edge of glaze. This is to allow for
the +/- 0.002" registration tolerance between layers.
2.6 Au and PtAu conductors shall
not terminate on PdAg filled through holes, but must terminate
at least 0.020" from the center point of the through hole.
3.0 Resistors:
3.1 Tolerances are based on a one
square resistor. The numbers are stated in inches. These
numbers are not absolute in any sense, but are based on
good test results. Tolerances as low as 0.1% are achievable
in our process. Our standard minimum size is 0.020" wide.
This rule may be broken only after consultation. In general,
the design practice should be to make a resistor as large
as possible. This is done to reduce process variability,
and to reduce laser trim time and cost.
| |
0.50% |
1% |
2% |
5% |
10% |
20% |
| 1 ohm square |
0.03 |
0.03 |
0.02 |
0.02 |
0.015 |
0.01 |
| 5 ohm square |
0.03 |
0.03 |
0.025 |
0.02 |
0.015 |
0.01 |
| 10 ohm square |
0.03 |
0.025 |
0.025 |
0.02 |
0.015 |
0.01 |
| 50 ohm square |
0.03 |
0.025 |
0.025 |
0.02 |
0.015 |
0.01 |
| 100 ohm square |
0.03 |
0.025 |
0.025 |
0.02 |
0.015 |
0.01 |
| 1k ohm square |
0.03 |
0.025 |
0.025 |
0.02 |
0.015 |
0.01 |
| 5K ohm square |
0.03 |
0.025 |
0.025 |
0.02 |
0.015 |
0.01 |
| 10K ohm square |
0.04 |
0.03 |
0.025 |
0.02 |
0.02 |
0.01 |
| 50K ohm square |
0.05 |
0.04 |
0.035 |
0.03 |
0.025 |
0.015 |
| 100K ohm square |
0.05 |
0.04 |
0.035 |
0.03 |
0.025 |
0.015 |
| 500K ohm square |
0.06 |
0.05 |
0.04 |
0.035 |
0.03 |
0.02 |
| IM ohm square |
0.07 |
0.06 |
0.05 |
0.04 |
0.035 |
0.03 |
| 5M ohm square |
NO |
NO |
0.07 |
0.065 |
0.06 |
0.05 |
| lOM ohm square |
NO |
NO |
0.08 |
0.075 |
0.065 |
0.05 |
3.2 Square count/aspect ratio: Aspect
ratios of 0.2 to 5 are reasonable for any given range.
This is not absolute. For example, a 10K ohm square resistor
decade can be extended out to a square count of 10 if
needed to eliminate a single 100K resistor print. Top
hat resistors are also acceptable for extending the range
of a given ink, or for functional trims. Serpentine resistors
may also be used for extending the range of a resistor.
If a linear trim would be advantageous, a shunted resistor
may be used.
3.3 Resistor terminations: The standard
overlap of a resistor onto the conductor is 0.010". This
may be shortened to no less than 0.005". The conductor
termination should be a minimum of 0.010" wider than the
resistor width, allowing for 0.005" on either side of
the resistor.
3.4 Resistor probe pads and locations:
All resistors need to have probe locations for laser trimming.
Additionally, low value and tight tolerance resistors
need to have specific probe locations noted. This would
include any resistor that has a tolerance equal to or
less than 1 ohm, or a conductor trace with a resistance
that exceeds the tolerance of an attached resistor. The
probe locations may be a component mounting pad or an
adjacent conductor area. The minimum probe pad size is
0.015" (either circle or square). Multilayer structures
may not have obvious probe locations. If this is the case,
these locations should be noted.
3.5 Wattage: In general, wattage
is derated to 50 watts per square inch to factor in laser
trimming; however, 100 watts per square inch material
is available upon request.
3.6 T.C.R.: T.C.R.'s of +/- 100ppm
are standard on PdAg and Au terminations. A +/- 50ppm
T.C.R. can be achieved, but may be design dependent. Resistors
terminated on PtAu may have a greater T.C.R.
4.0 Capacitor Layout:
4.1 The basic formula used to define
capacitor plate size is: C = 0.225KA/th C = capacitance
K = dielectric constant A = area of overlapping conductor
plates th = the thickness of the dielectric between the
plates
Note: Capacitance is expressed in
picofarads, and all dimensions are in inches.
4.2 Dielectrics constants available
are: A. K=4.5 B. K=8.0 C. K=25 - 500 (blendable series)
D. K=2000 - 10000 (The actual K is process dependent,
K = 10000 on ceramic with PdAg plates, K lowers dramatically
when embedded in an MCM structure, values achieved depend
on actual process steps involved.)
4.3 Capacitor tolerance: As fired
tolerance depends on the area of the capacitor plates.
A 10% tolerance will require at least an area of 0.0025
sq" for the low value materials. Capacitors less than
15pf will have an as fired value of +\- 20%. Capacitors
using K = 2000-10000 will have an as fired value of +\-
20%. Capacitors can be designed to be trimmed down to
value to achieve tighter tolerances.
4.4 Types of capacitors:
9.3.2
Standard distance from substrate edge to registration
mark edge = 0.015". Any deviation from standard distance
is to be specified and noted on fabrication drawings.