參數(shù)資料
型號: ISP1122
廠商: NXP Semiconductors N.V.
英文描述: Universal Serial Bus stand-alone hub
中文描述: 通用串行總線獨立的樞紐
文件頁數(shù): 42/48頁
文件大小: 1159K
代理商: ISP1122
Philips Semiconductors
ISP1122
USB stand-alone hub
Product specification
Rev. 03 — 29 March 2000
42 of 48
9397 750 07002
Philips Electronics N.V. 2000. All rights reserved.
18. Soldering
18.1 Introduction
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 IC packages. Wave soldering is often
preferred when through-hole and surface mount components are mixed on one
printed-circuit board. However, wave soldering is not always suitable for surface
mount ICs, or for printed-circuit boards with high population densities. In these
situations reflow soldering is often used.
18.2 Surface mount packages
18.2.1
Reflow soldering
Reflow soldering requires solder paste (a suspension of fine solder particles, flux 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 reflowing; for example, infrared/convection heating in a
conveyor type oven. Throughput times (preheating, soldering and cooling) vary
between 100 and 200 seconds depending on heating method.
Typical reflow peak temperatures range from 215 to 250
°
C. The top-surface
temperature of the packages should preferable be kept below 230
°
C.
18.2.2
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 specifically
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.
For packages with leads on four sides, the footprint must be placed at a 45
°
angle
to the transport direction of the printed-circuit board. The footprint must
incorporate solder thieves downstream and at the side corners.
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