scope:

This standard provides requirements for process control of conveyorized solder reflow ovens. It includes a methodology for performing temperature measurements over time to establish a baseline profile, and then provides requirements to verify repeatability through periodic verification of the oven profile.

This standard is not intended for the assembly product profile/recipe. For detailed information on development or verification of a product profile/recipe, see IPC-7530.

This standard does not address vapor phase processes. Batch ovens offer lower throughput and are also not covered in this standard.

Purpose

This standard provides baseline performance, periodic verification and performance repeatability requirements for reflow oven equipment.

Measurement Units

This standard uses International System of Units (SI) units [Imperial English equivalent units are in brackets for convenience]. The SI units used in this standard are Celsius (°C) [°F] for temperature and temperature tolerances.

Definition of Requirements

The words shall or shall not are used in the text of this document wherever there is a requirement for materials, preparation, process control or acceptance.

The word "should" reflects recommendations and is used to reflect general industry practices and procedures for guidance only.

Line drawings and illustrations are depicted herein to assist in the interpretation of the written requirements of this Standard. The text takes precedence over the figures.

Process Control Requirements

The primary goal of process control is to continually reduce variation in the processes, products, or services to provide products or processes meeting or exceeding User requirements. Process control tools such as IPC-9191, JESD557 or other User-approved system may be used as guidelines for implementing process control.

Users shall develop and implement a documented process control system for reflow soldering.

The documented process control system shall define process control and corrective action limits.

This may or may not be a statistical process control system. The use of "statistical process control" (SPC) should be based on factors such as design stability, lot size, production quantities, and the needs of the User.

Process control methodologies shall be used in the planning, implementation and evaluation of the reflow soldering processes. The philosophy, implementation strategies, tools and techniques may be applied in different sequences depending on the specific company, operation, or variable under consideration to relate process control and capability to end product requirements.

When a decision or requirement is to use a documented process control system for reflow soldering, failure to implement process corrective action and/or the use of continually ineffective corrective actions shall be grounds for disapproval of the reflow soldering process and associated documentation.

Order of Precedence

The contract shall take precedence over this Standard, referenced standards and drawings.

In the event of conflict, the following order of precedence applies:

1) Procurement as agreed and documented between customer and User.

2) Master drawing reflecting the customer's detailed requirements.

3) When invoked by the customer or per contractual agreement, this standard.

When documents other than this standard are cited, the order of precedence should be defined in the procurement documents.

Conflict

In the event of conflict between the requirements of this standard and the applicable drawing(s) and documentation, the applicable customer-approved drawing(s) and documentation govern.

Some examples of documentation include the contract, purchase order, technical data package, engineering specification or performance specification. In the event of a conflict between the text of this standard and the applicable documents cited herein, the text of this standard takes precedence. In the event of conflict between the requirements of this standard and drawing(s) and documentation that has not been customer approved, this standard governs.

Clause References

When a clause in this document is referenced, its subordinate clauses apply, unless the requirement references specific subordinate clauses.

Terms and Definitions

Other than those terms listed below, the definitions of terms used in this standard are in accordance with IPC-T-50.

Oven Profile

A graphical representation of temperature for a single or multiple locations on an assembly, plotted against time, during the reflow process. It may be a recommended ''baseline'' or Target Profile, or reflect actual measurements.

Profiling System

A data logger or measuring instrument for recording temperature and time data from thermocouples. Also known as a profiler.

Ramp

A controlled and uniform increase or decrease in temperature, represented as a slope on the oven profile across a set time interval. The magnitude of the slope is known as the Ramp Rate.

Recipe

A defined set of process parameters programmed into a reflow oven. It includes a specific conveyor speed and temperatures within each reflow zone, and possibly the flow rates of air or nitrogen. The recipe typically varies with the thermal mass and other heat transfer characteristics of the assembly being soldered.

Reflow Oven

A solder reflow system, typically using mostly convection heating in an air or nitrogen environment. Conveyorized systems incorporate multiple reflow zones in series.

Thermocouple

A thermocouple is a temperature-measuring device that uses two wire conductors made of dissimilar metals. The wires are connected at a single point. When hot or cold are applied to the thermocouple, the voltage difference between the exposed connection point and an insulated reference connection point is interpreted by a meter, which then converts the voltage difference into a displayed temperature.

User

The individual or organization responsible for controlling and performing reflow soldering.

Verification Test Vehicle

A reusable sample for thermal profiling used to measure reflow oven performance and repeatability.