Guidelines for Temperature Profiling for Mass Soldering ...

1 ASSOCIATION CONNECTING. ELECTRONICS INDUSTRIES . IPC-7530. Guidelines for Temperature Profiling for mass Soldering Processes (Reflow & Wave). IPC-7530. May 2001 A guide developed by IPC. 2215 Sanders Road, Northbrook, IL 60062-6135. Tel. Fax May 2001 IPC-7530. Table of Contents 1 INTRODUCTION .. 1 Setup and Base 7. Scope .. 1 Process Control .. 7. 1. 7 TECHNIQUES AND PROCEDURES FOR IN-LINE. Purpose .. 1 PROCESSES .. 7. Pre-Heating Limits .. 7. 2 REFERENCES .. 1. Profiling Frequency .. 7. IPC .. 1. Joint Industry Standard .. 1 Thermocouple Definition/Selection.

2 7. Thermocouple 7. 3 GENERIC PROCESS PROFILES .. 1. Thermocouple Wire Gauge .. 8. Wave Soldering .. 1. Insulation .. 8. Reflow 1. Wire 8. 4 Temperature PROFILING EQUIPMENT .. 3 Thermocouple Junction .. 8. Profiler Types .. 3 Life Expectancy/Deterioration (Sample Board Product 3 as well as Thermocouple) .. 8. Machine Profilers .. 4 Calibration and Test .. 8. Continuous Real-Time Thermal Profile Thermocouple Positioning .. 8. Monitoring .. 4 Wave Solder .. 8. Profiling Equipment Data Display 8. and Analysis .. 4 Thermocouple Attachment .. 8. 5 THEORY OF PROFILING EQUIPMENT Hi- Temperature Solder.

3 9. OPERATION .. 4 9. Basic Concepts .. 4 Polyimide 9. Data Output .. 5 Aluminum 9. Interpretation of 5 Embedded Thermocouple .. 9. Predictive Capability .. 5 Mechanical 9. Automated Prediction 6. External 6 Figures 6 EQUIPMENT ANALYSIS WITH MACHINE Figure 3-1 Dual-Wave Solder Profile PROFILING .. 6 Figure 3-2 Reflow 2. Issues .. 6 Figure 3-3 Curing Profile .. 3. Control .. 6 Figure 7-1 Thermocouple Attachment Reasons of Decreased 6 (Solder Method) .. 9. Assessment of Soldering Process .. 6 Figure 7-2 Thermocouple Attachment (Adhesive Method).. 9.

4 Characteristics of Equipment 7. Figure 7-3 Thermocouple Attachment Solutions .. 7 (Tape Method).. 9. iii May 2001 IPC-7530. Guidelines for Temperature Profiling for mass Soldering Processes (Reflow & Wave). 1 INTRODUCTION IPC-CA-821 General Requirements for Thermally Con- ductive Adhesives Scope This guideline document addresses the issues pertinent to Temperature profiling of electronic assemblies IPC-9501 PWB Assembly Process Simulation for Evalua- for mass Soldering processes (reflow and wave). tion of Electronic Components IPC-9502 PWB Assembly Soldering Process Guideline for Background During mass Soldering , it is important Electronic Components that all solder joints reach the minimum Soldering tempera - ture.

5 The minimum Soldering Temperature is the minimum IPC-9504 Assembly Process Simulation for Evaluation of Temperature necessary to assure metallurgical bonding of Non-IC Components (Preconditioning Non-IC Compo- the solder alloy and the base metals to be soldered. Metal- nents). lurgical bonding requires that both surfaces to be soldered, as well as the solder, reach this minimum Soldering tem- Joint Industry Standard1. perature for a sufficient time to allow the wetting of the IPC/EIA J-STD-001 Requirements for Soldered Electrical solder surfaces and the formation of a layer(s) of interme- and Electronic Assemblies tallic compound(s) of some of the base metal(s) with one or more constituents of the solder alloy.

6 As a practical mat- 3 GENERIC PROCESS PROFILES. ter, the minimum Soldering Temperature is somewhat (~25 C) above the melting Temperature (Liquidus tempera - Wave Soldering When profiling assemblies for wave ture) of the solder alloy. The solder joint on a given assem- Soldering , the following areas shall be monitored as seen in bly that reaches the minimum Soldering Temperature last Figure 3-1. (typically on or underneath one of the most massive com- Ramp Up: The rate of Temperature increase is controlled to ponents) has to be the one that determines the Temperature ensure the PWB, components and flux have sufficient time profile setting for a given assembly and a given Soldering to reach Soldering temperatures without degradation.

7 Process/machine. Thermal Spike: Thermal spike is measured to ensure com- mass Soldering requires controlled rates of heating and ponents are not exposed to excessive shock that can result subsequent cooling. However, too rapid a heating rate can in damage. damage printed wiring boards (PWBs) as well as compo- nents. High cooling rates can damage components and can Dwell Time: Dwell time is measured to ensure excessive result in Temperature gradients of sufficient magnitude to time in the solder does not occur which could result in warp PWBs and larger components and may fracture sol- damage to components and degrade flux.

8 Der joints. Maximum Topside Temperature : Maximum topside tem- It is for these reasons that appropriate Temperature profiling perature is monitored to ensure solder joints formed by is essential to assure solder joints of high quality. reflow do not revert to a liquid state. Purpose This document provides Guidelines for the Reflow Soldering When profiling assemblies for sol- construction of appropriate profiling test vehicles and vari- der reflow and adhesive cure, the following areas shall be ous techniques and methodologies for Temperature profil- monitored as seen in Figure 3-2 for solder paste.

9 Ing. Note: An example of adhesive, underfill or other material curing profile is shown in Figure 3-3. 2 REFERENCES. Ramp: This is the portion of the profile where the assem- IPC1 bly is heated from ambient Temperature at a predetermined rate. Controlling the ramp is necessary to prevent compo- IPC-T-50 Terms and Definitions for Interconnecting and nent damage. It also allows the flux solvents to evaporate Packaging Electronic Circuits prior to the flux being fully active. 1. IPC, 2215 Sanders Road, Northbrook, IL 60062. 1.