參數(shù)資料
型號: 935270050128
廠商: NXP SEMICONDUCTORS
元件分類: 微控制器/微處理器
英文描述: 4 CHANNEL(S), 5M bps, SERIAL COMM CONTROLLER, PQFP64
封裝: 10 X 10 MM, 1.40 MM HEIGHT, PLASTIC, MS-026, SOT-314-2, LQFP-64
文件頁數(shù): 43/55頁
文件大小: 706K
代理商: 935270050128
Philips Semiconductors
SC16C654/654D
Quad UART with 64-byte FIFO and infrared (IrDA) encoder/decoder
Product data
Rev. 02 — 13 March 2003
48 of 52
9397 750 10985
Koninklijke Philips Electronics N.V. 2003. All rights reserved.
12. Soldering
12.1 Introduction to soldering surface mount packages
This text gives a very brief insight to a complex technology. A more in-depth account
of soldering ICs can be found in our
Data Handbook IC26; Integrated Circuit
Packages (document order number 9398 652 90011).
There is no soldering method that is ideal for all surface mount IC packages. Wave
soldering can still be used for certain surface mount ICs, but it is not suitable for ne
pitch SMDs. In these situations reow soldering is recommended.
12.2 Reow soldering
Reow soldering requires solder paste (a suspension of ne solder particles, ux and
binding agent) to be applied to the printed-circuit board by screen printing, stencilling
or pressure-syringe dispensing before package placement.
Several methods exist for reowing; for example, convection or convection/infrared
heating in a conveyor type oven. Throughput times (preheating, soldering and
cooling) vary between 100 and 200 seconds depending on heating method.
Typical reow peak temperatures range from 215 to 250
°C. The top-surface
temperature of the packages should preferably be kept:
below 220
°C for all the BGA packages and packages with a thickness ≥ 2.5mm
and packages with a thickness <2.5 mm and a volume
≥350 mm3 so called
thick/large packages
below 235
°C for packages with a thickness <2.5 mm and a volume <350 mm3 so
called small/thin packages.
12.3 Wave soldering
Conventional single wave soldering is not recommended for surface mount devices
(SMDs) or printed-circuit boards with a high component density, as solder bridging
and non-wetting can present major problems.
To overcome these problems the double-wave soldering method was specically
developed.
If wave soldering is used the following conditions must be observed for optimal
results:
Use a double-wave soldering method comprising a turbulent wave with high
upward pressure followed by a smooth laminar wave.
For packages with leads on two sides and a pitch (e):
larger than or equal to 1.27 mm, the footprint longitudinal axis is preferred to be
parallel to the transport direction of the printed-circuit board;
smaller than 1.27 mm, the footprint longitudinal axis must be parallel to the
transport direction of the printed-circuit board.
The footprint must incorporate solder thieves at the downstream end.
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