LPC2917 datasheet(59/68 Pages) PHILIPS

59 / 68 page

LPC2917_19_1

Preliminary data sheet

Rev. 1.01 — 15 November 2007

59 of 68

NXP Semiconductors

LPC2917/19

ARM9 microcontroller with CAN and LIN

14. Soldering

14.1 Introduction

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 fine pitch

SMDs. In these situations reflow soldering is recommended.

14.2 Through-hole mount packages

14.2.1 Soldering by dipping or by solder wave

Typical dwell time of the leads in the wave ranges from 3 seconds to 4 seconds at 250

°C

or 265

°C, depending on solder material applied, SnPb or Pb-free respectively.

The total contact time of successive solder waves must not exceed 5 seconds.

The device may be mounted up to the seating plane, but the temperature of the plastic

body must not exceed the specified maximum storage temperature (Tstg(max)). If the

printed-circuit board has been pre-heated, forced cooling may be necessary immediately

after soldering to keep the temperature within the permissible limit.

14.2.2 Manual soldering

Apply the soldering iron (24 V or less) to the lead(s) of the package, either below the

seating plane or not more than 2 mm above it. If the temperature of the soldering iron bit is

less than 300

°C it may remain in contact for up to 10 seconds. If the bit temperature is

between 300

°C and 400 °C, contact may be up to 5 seconds.

14.3 Surface mount packages

14.3.1 Reflow soldering

Key characteristics in reflow soldering are:

• Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to

higher minimum peak temperatures (see Figure 16) than a PbSn process, thus

reducing the process window

• Solder paste printing issues including smearing, release, and adjusting the process

window for a mix of large and small components on one board

• Reflow temperature profile; this profile includes preheat, reflow (in which the board is

heated to the peak temperature) and cooling down. It is imperative that the peak

temperature is high enough for the solder to make reliable solder joints (a solder paste

characteristic). In addition, the peak temperature must be low enough that the

packages and/or boards are not damaged. The peak temperature of the package

depends on package thickness and volume and is classified in accordance with

Table 32 and 33

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