Philips Semiconductors Package information Soldering INTRODUCTION SURFACE MOUNTED PACKAGES There is no soldering method that is ideal for all IC packages. Wave soldering is often preferred when through-hole and surface mounted components are mixed on one printed-circuit board. However, wave soldering is not always suitable for surface mounted ICs, or for printed-circuits with high population densities. In these situations reflow soldering is often used. Table 2 TYPE This text gives a very brief insight to a complex technology. A more in-depth account of soldering ICs can be found in our "IC Package Databook" (order code 9397 750 0011). THROUGH-HOLE MOUNTED PACKAGES Table 1 Types of through-hole mounted packages TYPE plastic dual in-line package SDIP plastic shrink dual in-line package HDIP plastic heat-dissipating dual in-line package DBS plastic dual in-line bent from a single in-line package SIL plastic single in-line package SO plastic small outline package SSOP plastic shrink small outline package TSSOP plastic thin shrink small outline package VSO plastic very small outline package QFP plastic quad flat package LQFP plastic low profile quad flat package SQFP plastic shrink quad flat package TQFP plastic thin quad flat package PLCC plastic leaded chip carrier Reflow soldering techniques are suitable for all SMD packages, ease of soldering varies with the type of package as indicated in Table <.Normal_XRef>3. The choice of heating method may be influenced by larger plastic packages (QFP or PLCC with 44 leads, or more). If infrared or vapour phase heating is used and the large packages are not absolutely dry (less than 0.1% moisture content by weight), vaporization of the small amount of moisture in them can cause cracking of the plastic body. For more information on moisture prevention, refer to the Drypack chapter in our "Quality Reference Handbook" (order code 9397 750 00192). Soldering by dipping or wave The maximum permissible temperature of the solder is 260 C; solder at this temperature must not be in contact with the joint for more than 5 seconds. The total contact time of successive solder waves must not exceed 5 seconds. The device may be mounted 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. Repairing soldered joints Apply a low voltage soldering iron (less than 24 V) to the lead(s) of the package, 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 and 400 C, contact may be up to 5 seconds. 1995 Oct 26 DESCRIPTION Reflow soldering DESCRIPTION DIP Types of surface mounted packages 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 techniques exist for reflowing; for example, thermal conduction by heated belt. Dwell times vary between 50 and 300 seconds depending on heating method. Typical reflow temperatures range from 215 to 250 C. Preheating is necessary to dry the paste and evaporate the binding agent. Preheating duration: 45 minutes at 45 C. 1728 Philips Semiconductors Package information Table 3 Soldering Suitability of surface mounted packages for various soldering methods: rating from `a' to `d': `a' indicates most suitable (soldering is not difficult); `d' indicates least suitable (soldering is achievable with difficulty). REFLOW METHOD INFRARED HOT BELT HOT GAS VAPOUR PHASE RESISTANCE DOUBLE WAVE METHOD SO a a a a d a SSOP a a a c d c TSSOP b b b c d d VSO b b a b a b QFP b b a c a c LQFP b b a c d d SQFP b b a c d d TQFP b b a c d d PLCC c b b d d b PACKAGE TYPE Wave soldering Wave soldering is not recommended for SSOP, TSSOP, QFP, LQFP, SQFP or TQFP packages, this is because of the likelihood of solder bridging due to closely-spaced leads and the possibility of incomplete solder penetration in multi-lead devices. * LQFP except LQFP32 (SOT401-1), LQFP48 (SOT313-1, SOT313-2), LQFP64 (SOT314-2), LQFP80 (SOT315-1); these are not suitable for wave soldering. * TQFP except TQFP64 (SOT357-1), TQFP80 (SOT375-1) and TQFP100 (SOT386-1); these are not suitable for wave soldering. SQFP are not suitable for wave soldering. If wave soldering cannot be avoided, the following conditions must be observed: * A double-wave (a turbulent wave with high upward pressure followed by a smooth laminar wave) soldering technique should be used. * For SSOP, TSSOP and VSO packages, the longitudinal axis of the package footprint must be parallel to the solder flow and must incorporate solder thieves at the downstream end. * For QFP, LQFP and TQFP packages, the footprint must be at an angle of 45 to the board direction and must incorporate solder thieves downstream and at the side corners. Even with these conditions, consider wave soldering only for the following package types: * SO * VSO * PLCC * SSOP only with body width 4.4 mm, e.g. SSOP16 (SOT369-1) or SSOP20 (SOT266-1). During placement and before soldering, the package must be fixed with a droplet of adhesive. The adhesive can be applied by screen printing, pin transfer or syringe dispensing. The package can be soldered after the adhesive is cured. Maximum permissible solder temperature is 260 C, and maximum duration of package immersion in solder is 10 seconds, if cooled to less than 150 C within 6 seconds. Typical dwell time is 4 seconds at 250 C. A mildly-activated flux will eliminate the need for removal of corrosive residues in most applications. Repairing soldered joints Fix the component by first soldering two diagonallyopposite end leads. Use only a low voltage soldering iron (less than 24 V) applied to the flat part of the lead. Contact time must be limited to 10 seconds at up to 300 C. When using a dedicated tool, all other leads can be soldered in one operation within 2 to 5 seconds between 270 and 320 C. * QFP except QFP52 (SOT379-1), QFP100 (SOT317-1, SOT317-2, SOT382-1) and QFP160 (SOT322-1); these are not suitable for wave soldering. 1995 Oct 26 1729