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Step Soldering by Heater Block

IP.com Disclosure Number: IPCOM000113598D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Ohkuma, H: AUTHOR

Abstract

This article describes a soldering method by using heater block of which process parameter, Z-axis pressure and Z-axis movement, can be changed during soldering operation to be applied for such fine pitch leads as outer leads of TCP or QFP in order to prevent solder bridges and also to improve the joint reliability.

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Step Soldering by Heater Block

       This article describes a soldering method by using heater
block of which process parameter, Z-axis pressure and Z-axis
movement, can be changed during soldering operation to be applied for
such fine pitch leads as outer leads of TCP or QFP in order to
prevent solder bridges and also to improve the joint reliability.

Fig. 1 shows the process flow of this soldering technique.

      Fig. 1(a) shows the condition when the heater block moves down
towards the surfaces of solder pads with relatively higher pressure
called initial pressure P1.  At this stage, the heater block contacts
all solder pads via leads.  The initial pressure should be high
enough to flatten the solder height of all copper pads to assure the
steady contact of heater block.

      Fig. 1(b) shows the condition when each solder pad is heated up
below the melting point of solder, and at this temperature, the
pressure of the heater block is automatically reset to P2 lower than
the initial pressure P1 in order to prevent solder bridges when
solder melt.

      Fig. 1(c) shows the condition when solder melt and heater block
moves down towards the copper pad surfaces with lower pressure P2.
At this stage, the melting solder is slowly pushed away from the
underneath of the leads without solder bridges.

      Fig. 1(d) shows the condition when the heater block moves up a
little to suck in solder between leads and copper pads by taking
advantage of capilla...