Nexperia AN10343 Instructions d'installation et d'utilisation
AN10343
MicroPak soldering information
Rev. 3.0 — 31 May 2021 application note
Document information
Information Content
Keywords MicroPak, footprint, Ball Grid Array (BGA), Wafer-Level Chip Scale Package (WLCSP)
Abstract This application note describes evaluation of recommended solder land patterns for mounting
MicroPak packages.
Nexperia AN10343
MicroPak soldering information
1. Introduction
Nexperia Semiconductors’ PicoGate and MicroPak packages are approximately ten to fifteen
times smaller than conventional SO14 packages, providing significant miniaturization in space-
constrained applications. They are available in a wide range of logic functions with a wide range of
choices and deliver the right levels of performance.
PicoGate and MicroPak devices include single-, dual-, and triple-gate functions and are housed
in 5-, 6-, 8- and 10-pin packages with selectable functions. To support the widest range of
applications, every product in the portfolio is specified for high-temperature operation (-40
°C to +125 °C). Since they perform the most popular functions and either meet or exceed
competitive specifications, they eliminate single-source problems.
Driven by applications with a very small circuit board mounting area, the PicoGate logic family
offers the most popular logic functions for space-constrained systems such as cellular phones,
pagers, and portable consumer products (CD players, VCRs, cameras, hard disks, notebook
computers, PC cards, CD ROMs, and Personal Digital Assistants (PDAs)). They can also be used
as simple glue/repair logic to implement last minute design changes or to eliminate dependence on
intricate line layout patterns and to simplify routing.
This application note describes the following mounting methods for MicroPak packages:
•MicroPak footprint
•SOT886/833-1 MicroPak on WLCSP/BGA footprint and vice versa
•SOT996-2 MicroPak on VSSOP8 footprint and vice versa
2. MicroPak overview
2.1. Package description
The MicroPak package is a near Chips Scale Package (CSP) Land Grid Array (LGA) type plastic
encapsulated package with a copper lead frame base. The package has no leads or bumps with
peripheral land terminals at the bottom of the package. The terminals are soldered to solder lands
on the Printed-Circuit Board (PCB), after solder paste is deposited.
An overview of released MicroPak packages is given in Table 1.
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application note Rev. 3.0 — 31 May 2021 2 / 32
Nexperia AN10343
MicroPak soldering information
Table 1. Overview MicroPak packages
Properties Number of pins
Pitch [mm] Height [mm] 5 or 6 8 10 16
0.3 0.35 SOT1115
019aab124
SOT1115
SOT1116
019aab125
SOT1116
- -
0.35 0.5/0.35 SOT891/SOT1202
019aab126
SOT891/SOT1202
SOT1089/SOT1203
019aab127
SOT1089/SOT1203
SOT1081-1
019aab128
SOT1081
-
0.5
(Dual-in-line)
0.5 SOT886
019aab129
SOT886
SOT833-1
019aab130
SOT833
- -
AN10343 All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2021. All rights reserved
application note Rev. 3.0 — 31 May 2021 3 / 32
Nexperia AN10343
MicroPak soldering information
Properties Number of pins
Pitch [mm] Height [mm] 5 or 6 8 10 16
0.5 0.5 - SOT902-1
019aab131
SOT902
SOT1049-1
019aab132
SOT1049
SOT1039-1
019aab133
SOT1039
0.5
(VSSOP8
replacement)
0.5 - SOT996-2
019aab134
SOT996
- -
AN10343 All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2021. All rights reserved
application note Rev. 3.0 — 31 May 2021 4 / 32
Nexperia AN10343
MicroPak soldering information
3. MicroPak soldering information
3.1. Solder paste
The following solder pastes were used in the evaluation and gave satisfactory results:
•PbSn paste: Alpha Metals Omnix 5002 (62 % Sn, 36 % Pb, 2 % Ag)
•SAC paste: Alpha Metals Omnix 310 (95.5 % Sn, 4 % Ag, 0.5 % Cu)
Both these solder pastes are 'no-clean'; due to the small stand-off height of the MicroPak, proper
cleaning underneath the package is not possible.
Both Pb or Pb-free solder can be used, although it is advised to use Pb-free solder paste as this is
required by European legislation from July 2006 onwards.
A wide variety of Pb-free solder pastes is available, containing combinations of tin, copper,
antimony, silver, bismuth, indium, and other elements. The different types of Pb-free solder pastes
have a wide range of melting temperatures. Solders with a high melting point may be more suitable
for the automotive industry, whereas solders with a low melting point can be used for soldering
consumer IC packages.
The most common substitute for SnPb solder, is Pb-free paste SAC, which is a combination of tin
(Sn), silver (Ag), and copper (Cu). These three elements are usually in the range of 3 % to 4 % of
Ag and 0 % to 1 % of Cu, which is near eutectic. SAC typically has a melting temperature of around
217 °C, and requires a reflow temperature of more than 235 °C.
Table 2. Typical solder paste characteristics
Solder (near eutectic alloys) Melting temperature Minimum peak reflow temperature
SnPb 183 °C 215 °C
SAC 217 °C 235 °C
A no-clean solder paste does not require cleaning after reflow soldering and is therefore preferred,
provided that this is possible within the process window. If a no-clean paste is used, flux residues
may be visible on the board after reflow.
For more information on the solder paste, please contact your solder paste supplier.
3.2. Moisture sensitivity level and storage
The MicroPak components have a very good package moisture resistance. The Moisture
Sensitivity Level (MSL) according to JEDEC-STD-020D is MSL1.
Table 3. Pb-free process - Package classification reflow temperatures (from J-STD-020D)
Package thickness Volume
(<350 mm3)
Volume
(350 mm3 to 2000 mm3)
Volume
(>2000 mm3)
<1.6 mm 260 °C 260 °C 260 °C
1.6 mm to 2.5 mm 260 °C 250 °C 245 °C
>2.5 mm 250 °C 245 °C 245 °C
3.3. Stencil
Table 4 gives the recommended electroformed stencil thickness for MicroPak packages with a
terminal pitch of greater than or equal to 0.5 mm, between 0.4 mm to 0.5 mm and less than or
equal to 0.4 mm. Side wall roughness of the apertures should be smooth to improve the solder
paste release.
AN10343 All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2021. All rights reserved
application note Rev. 3.0 — 31 May 2021 5 / 32
Nexperia AN10343
MicroPak soldering information
Table 4. Typical stencil thicknesses
IC package pitch Stencil thickness
≥0.5 mm 150 µm
0.4 mm to 0.5 mm 100 µm or 125 µm
≤0.4 100 µm
3.4. MicroPak placement
The required placement accuracy of a package depends on a variety of factors, such as package
size and the terminal pitch, but also the package type itself. During reflow, when the solder is
molten, a package that has not been placed perfectly may center itself on the pads: this is referred
to as self-alignment. Therefore, the required placement accuracy of a package may be less tight
if it is a trusted self-aligner. It is known, for example, that BGAs are good at self-alignment, as
the package body essentially rests on a number of droplets of molten solder, resulting in minimal
friction.
Table 5 gives typical placement tolerances as a function of the IC package terminal pitch.
Table 5. Typical placement accuracies
Package terminal pitch Placement tolerance
≥0.65 mm 100 µm
<0.65 mm 50 µm
3.5. Reflow soldering
The most important step in reflow soldering is reflow itself, when the solder paste deposits melt and
soldered joints are formed. This is achieved by passing the boards through an oven and exposing
them to a temperature profile that varies in time. A temperature profile essentially consists of three
phases:
1. Preheat: the board is warmed up to a temperature that is lower than the melting point of the
solder alloy
2. Reflow: the board is heated to a peak temperature that is well above the melting point of the
solder, but below the temperature at which the components and board’s Organic Solderability
Preservative (OSP) finish are damaged
3. Cooling down: the board is cooled down rapidly, so that soldered joints freeze before the board
exits the oven
The peak temperature during reflow has an upper and a lower limit:
•Lower limit of peak temperature; the minimum peak temperature must be at least high enough
for the solder to make reliable solder joints; this is determined by solder paste characteristics;
contact your paste supplier for details
•The upper limit of the peak temperature must be lower than:
•the maximum temperature the component can withstand according to the specification
•the temperature at which the board or the components on the board are damaged (contact
your board supplier for details)
Examples of a general purpose Pb-free reflow profile are shown in Fig. 1 and Table 6.
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application note Rev. 3.0 — 31 May 2021 6 / 32
Nexperia AN10343
MicroPak soldering information
019aab067
tph
β
χ
tr
Tp(max)
temperature
time
Tph(min)
α
Tph(max)
Tr(max)
Tp(min)
tph
time to peak
Fig. 1. Example of a general purpose Pb-free reflow profile
Table 6. Explanation of the reflow temperature profile
Parameter Value(s) Typical value(s) Remark
α 1 °C/s to 5 °C/s 2 °C/s determined by component and board type and finish
ß 1°C/s to 5 °C/s 1.5 °C/s determined by component and board type and finish
X -2 °C/s to +6 °C - determined by component and board type and finish
Tph(min) to
Tph(max)
120 °C to 200 °C 160 °C depends on the solder paste used - contact your
solder paste supplier
tph 0 s to 180 s 100 s to 180 s depends on the solder paste used - contact your
solder paste supplier
tr30 s to 90 s 40 s to 70 s depends on board finish and solder paste voiding
behavior - contact your board and solder paste
supplier
Tp(min) 235 °C - temperature measured in the solder at the coldest
spot [1]
Tp(max) 260 °C 245 °C depends on the board and the board finish in case of
OSP and the most temperature-sensitive component
used on the board [1]
reflow atmosphere - - general purpose reflow is under air atmosphere,
nitrogen reflow is allowed
[1] Delta between Tp(min) and Tp(max) preferably limited to 10 °C.
Additional soldering information and guidelines for board-mounting of surface-mount IC packages
are described in AN10365 ‘Surface mount reflow soldering description’.
3.6. MicroPak soldering information for WLCSP/BGA footprint
Fig. 2 shows the recommended solder land pattern for mounting the MicroPak XSON6 (SOT886)
package. Using this pattern results in a very good electrical and mechanical connection which can
also be inspected and tested for continuity. Using the land grid array package eliminates the co-
planarity issues of leaded and WLCSP/BGA type devices.
The 6-pad MicroPak package available from NXP Semiconductors is alternately second-sourced
by Fairchild Semiconductors. Although the footprint for the Texas Instruments WLCSP/BGA
package is physically smaller, the MicroPak very easily fits the same footprint. Fig. 3 shows the
AN10343 All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2021. All rights reserved
application note Rev. 3.0 — 31 May 2021 7 / 32
Nexperia AN10343
MicroPak soldering information
recommended solder land pattern for the WLCSP/BGA package and the footprint of the MicroPak
SOT886.
Placing the WLCSP/BGA package on the MicroPak footprint is not recommended. As can be seen
in Fig. 4 the larger land pattern for the MicroPak may cause solder starvation due to the limited
amount of solder in the package solder ball. Solder paste would help, although there will be limited
mechanical contact. This is true for the larger Pb-free WLCSP/BGA balls. Even less mechanical
contact is achieved with the smaller PbSn WLCSP/BGA balls. Fig. 5 shows the recommended
solder land pattern for the WLCSP/BGA package and the footprint of the MicroPak SOT833-1.
001aac255
0.49
0.3
0.5
1
0.52 0.49 solder land pattern
package footprint
dimensions in mm
Fig. 2. MicroPack footprint
001aac256
0.5 mm
solder land pattern
package footprint
Fig. 3. MicroPack SOT886 on BGA footprint
0.5 mm
0.225 mm
001aac257
solder land pattern
package footprint
Fig. 4. BGA on MicroPack footprint
001aan102
0.5 mm
solder land pattern
package footprint
Fig. 5. MicroPack SOT833-1 on BGA footprint
3.7. SOT996-2 MicroPak soldering information for VSSOP8 footprint
Fig 6 a shows the recommended solder land pattern footprint for mounting the MicroPak XSON8
(SOT996-2) package. Using this pattern results in a very good electrical and mechanical
connection which can also be inspected and tested for continuity. Fig 6 b shows how the MicroPak
XSON8 (SOT996-2) package fits the VSSOP8 (SOT765-1) solder land pattern footprint. Fig 6 c
shows the VSSOP8 (SOT765-1) package on its VSSOP8 solder land pattern footprint.
AN10343 All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2021. All rights reserved
application note Rev. 3.0 — 31 May 2021 8 / 32
Nexperia AN10343
MicroPak soldering information
019aab069
component
Cu footprint
0.25
1.10
1.00
a. XSON8/SOT996-2
package superimposed on
its recommended solder land
pattern footprint
019aab070
component
Cu footprint
0.30
0.40
0.75
b. XSON8/SOT996-2 package
superimposed on solder land
pattern footprint for VSSOP8/
SOT765-1
019aab071
component
Cu footprint
0.30
0.40
0.75
c. VSSOP8/SOT765-1
package superimposed on its
solder land pattern footprint
Fig. 6. Solder land pattern footprints for mounting package MicroPak XSON8U (SOT996-2)
4. Manual repair of leadless MicroPak
In general, replacing a defective component on a soldered board, during repair or rework, can be
carried out either manually or with a dedicated repair station.
The rework process should consist of the following steps:
1. Dry bake the board and the new component, if necessary
2. Mark the position of the old component
3. Remove the old component
4. Prepare the site
5. Print solder paste on the new component
6. Reflow the solder paste on the new component
7. Place the new component on the board
8. Solder the new component
9. Visual inspection, electrical measurement, and X-ray inspection
The above steps are summarized in Fig. 7.
AN10343 All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2021. All rights reserved
application note Rev. 3.0 — 31 May 2021 9 / 32
Nexperia AN10343
MicroPak soldering information
019aab068
MARK POSITION
OLD COMPONENT
SITE
PREPARATION
PRINT PASTE ON
NEW
COMPONENT
REFLOW PASTE
manual
repair only
repair
station only
both
REMOVE OLD
COMPONENT WITH
HOT AIR GUN
DE-SOLDER OLD
COMPONENT WITH
INFRARED
PLACE NEW
COMPONENT
MANUALLY
PLACE NEW
COMPONENT USING
REPAIR STATION
DRY BAKE
BOARD AND NEW
COMPONENT
INSPECTION
SOLDER NEW
COMPONENT WITH
HOT AIR GUN
SOLDER NEW
COMPONENT WITH
INFRARED
Fig. 7. Rework process steps
AN10343 All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2021. All rights reserved
application note Rev. 3.0 — 31 May 2021 10 / 32
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