Assembly of LPCC Packages AN-0001

Assembly of LPCC Packages
Surface Mount Assembly and Handling of
1.0 Overview
ANADIGICS power amplifiers are typically packaged in a Leadless Plastic Chip Carrier (LPCC) package.
These LPCC packages have two types of pads, mounting pads and a thermal pad, both of which must be
correctly soldered for proper electrical contact to the PCB. The appropriate steps should be taken during
PCB design and assembly to guarantee optimum performance from the power amplifiers. This
application note outlines the steps necessary for the handling and assembly of ANADIGICS power
2.0 Requirements
2.1 PCB Design Guidelines:
1. PCB land and solder masking recommendations are shown in Figure 1.
A = Clearance from PCB thermal pad to solder mask opening, 0.0635 mm minimum
B = Clearance from edge of PCB thermal pad to PCB land, 0.2 mm minimum
C = Clearance from PCB land edge to solder mask opening to be as tight as
possible to ensure that some solder mask remains between PCB pads
D = PCB land length = LPCC solder pad length + 0.1mm
E = PCB land width = LPCC solder pad width
Figure 1. PCB Land and Solder Mask Recommendations.
2. Plated-Through Holes or vias should not be used in the mounting pads for the IC
circuit connections.
3. Thermal vias should be used on the PCB thermal pad (middle ground pad) to improve
thermal conductivity from the device to a copper ground plane area on the reverse side of
the printed circuit board. The number of vias depends on the package thermal
requirements, as determined by thermal simulation or actual testing.
4. Increasing the number of vias through the printed circuit board will improve the thermal
conductivity to the reverse side ground plane and external heat sink. In general, adding
more metal through the PC board under the IC will improve operational heat transfer, but
will require careful attention to uniform heating of the board during assembly.
5. For best thermal performance, provision should be made to provide a thermal path from
the reverse side ground plane to an external heat sink.
2.2 Package Handling
1. ESD precautions must be observed at all times when handling these packages.
2. Packages should be used in accordance with their MSL (Moisture Sensitivity Level) rating
found on the device datasheet.
3. MSL-3 packages should be used 168 hours after they have been removed from the
sealed moisture barrier bag. After 168 hours, packages should be baked for 24 hours at
125 °C before usage or resealing in a sealed moisture barrier bag.
4. MSL-2 packages have a lifespan of 12 months after they have been removed from a
sealed moisture barrier bag, after which they must be baked as above before usage.
5. MSL-1 packages have an infinite lifespan after initial baking in the factory.
3.0 Assembly Process
3.1 Stencil Design & Solder Paste Application
1. Stainless steel stencils are recommended for solder paste application.
2. A stencil thickness of 0.125 – 0.150 mm (5 – 6 mils) is recommended for screening.
3. For the PCB thermal pad, solder paste should be printed on the PCB by designing a
stencil with an array of smaller openings that sum to 50% of the LPCC thermal pad area
as shown in Figure 2.
4. The aperture opening for the signal pads should be between 50-80% of the LPCC pad
area as shown in Figure 3.
5. Optionally, for better solder paste release, the aperture walls should be trapezoidal and
the corners rounded.
6. The fine pitch of the IC leads requires accurate alignment of the stencil and the printed
circuit board. The stencil and printed circuit assembly should be aligned to within + 1 mil
prior to application of the solder paste.
7. No-clean flux is recommended since flux from underneath the thermal pad will be difficult
to clean if water-soluble flux is used.
3.2 Soldering Options & Package Placement
1. Hand soldering of these devices is not recommended even for prototypes.
2. Infrared or Convection mass reflow soldering is the preferred method of LPCC
Figure 2. Solder Paste Application on Paddle:
Solder paste should be applied through an array of squares (or circles)
which totals 50 % of the total area of the paddle
Minimum 50%
62 % coverage
Maximum 80%
Figure 3. Solder Paste Application on Pins.
3. It is extremely difficult to supply proper reflow heating to the ground pad/thermal
connection in a manual environment. Heat must be simultaneously applied to both the
top and bottom side of the PCB assembly to ensure uniform reflow heat under the IC
thermal pad. If insufficient heat is applied, the solder paste under the thermal pad will not
reflow. In the case where the LPCC package houses a power amplifier, the thermal pad
will not be properly connected to the heat sink and will likely result in early device
failure. Conversely, if excess heat is applied, the device may be damaged.
4. Manual placement and/or manual repositioning of LPCC packages is not recommended.
3.3 Solder Reflow Profile
1. A solder composition of 63% Sn, 37% Pb for the mounting of surface mount packages is
recommended. The PCB assembly should be instrumented and the reflow oven’s
process parameters established to ensure the solder paste manufacturer’s reflow profile
specification is met during the assembly process. See Figure 4.
2. The maximum PCB temperature recommended by the supplier must not be exceeded.
220 °C
183 °C
(45-75 sec.)
Cool Down
Figure 4. Solder Reflow Profile.
3.4 Rework
A package rework tool with vacuum pick-up should be used.
A bottom PCB heater should be used to preheat the board within 1" of the rework site.
Excess solder must be removed before new part placement.
The new package should be placed using pick and place equipment.
Reflow conditions should be followed as mentioned before.
3.5 Solder Process Inspection
1. The vias on the back of the PCB should be filled with solder as an indication of good
connection of the LPCC thermal pad to the PCB. A thermal pad that is not soldered
properly may cause device failure and will accelerate the MTTF (Median Time To
2. After reflow, verify that there is no bridging of solder to exposed circuitry, vias, or other
pins that could cause shorts and affect performance.
141 Mount Bethel Road
Warren, New Jersey 07059,U.S.A.
Tel: +1(908)668-5000
Fax: +1(908)668-5132
E-mail: [email protected]
ANADIGICS, Inc. reserves the right to make changes to its products or to discontinue any product at any time without notice. The product
specifications contained in Advanced Product Information sheets and Preliminary Data Sheets are subject to change prior to a product’s formal
introduction. Information in Data Sheets have been carefully checked and are assumed to be reliable; however, ANADIGICS assumes no
responsibilities for inaccuracies. ANADIGICS strongly urges customers to verify that the information they are using is current before placing orders.
ANADIGICS products are not intended for use in life support appliances, devices or systems. Use of an ANADIGICS product in any such application
without written consent is prohibited.