NXP Semiconductors LPC2917, LPC2919 Soldering, Introduction, Through-hole mount packages

NXP Semiconductors

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DLPC2917/19

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14. Soldering

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14.1 Introduction	DRAFT DRAFT
soldering can still be used for certain surface mount ICs, but it is not suitable for fine pitchDRAFT			D
There is no soldering method that is ideal for all surface mount IC packages. Wave
SMDs. In these situations reflow soldering is recommended.		DRA

14.2 Through-hole mount packages

14.2.1Soldering 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.

14.2.2Manual 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

14.3.1Reflow 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

LPC2917_19_1 © NXP B.V. 2007. All rights reserved.

Preliminary data sheet Rev. 1.01 — 15 November 2007 59 of 68