APE Rework Principles Advanced Programming in Vision Rework

APE Rework Principles Advanced Programming in Vision Rework

Features of APE Technology n n n n n Convection Hot Air Flexible Segment Profiling Open Oven Nozzle Design Component Inspection after Placement and prior to Reflow “Real Time” Profile Development Optimum Power Performance Optimum Low Velocity – High Volume Air Flow Thermocouple Profile Development Superior Vision and Component Viewing Robust Design

Advantages of APE Hot Air Technology n Hot Air Convection replicates the original Oven Manufacturing Profile and environment (Up to 16 Zones/Segments). n Safe Lower Temperatures due to Heater and delivery design resulting in improved Power, Low velocity and High Volume Air Flow. n Extended Heater life. n Placement and Reflow is separated allowing installation of larger Heaters with greater Air Volume. n Separating the Placement and Reflow stations enables inspection of the component after Placement and prior to Reflow. n An open Nozzle design provides an improved Temperature Delta across component and PCB and can rework components in tight proximity. n PID Step Profile Development allows greater flexibility in ramp-soak profile design as opposed to Zone Profiling. n Convection Under Board Heating can be operated simultaneously with Top Reflow Heater from the First Segment. n Extremely Robust and Long Life Technology with Low Running Costs

Single Station Versus Dual Station Machines n n n Placement and Reflow: A number of Rework machines Place and Reflow in the same location – at first glance this appears to be an advantage but it has the disadvantage of forcing a smaller Heater design resulting in Lower Air Volume and a Higher Air Velocity, which creates greater turbulence to and around the component. Recently APE’s (patented) higher Power methodology has been generally adopted in the industry to address Lead-Free demands. Heaters are commonly running at greater than a 1000 Watts in a confined chamber with the result that they burn out at a rapid rate – often at a frequency of one Heater per month. This single station concept is contrary to an APE Dual Station principle that not only allows a Heater design with a High Power Element but also provides for a Heater with an “HIGHER VOLUME” and “LOWER VELOCITY” Air Flow. This is only possible when a Placement and Reflow Station is separated. It is unusual for an APE Heater to burn out within 12 months of continuous use. Single Station Rework versus Dual Station Rework: With a single station system the board remains stationary – this is again seen as an advantage but in practice the restricted Heater design coupled with the inability to view the component after Placement is a far greater disadvantage than the smooth transition from Placement to Reflow with an APE system.

Comparison of APE Hot Air Technology with Competition n n n n Open Oven Nozzle RAMP-SOAK Profile Development versus Closed Nozzle Zone Ramping : There are three target Temperature Zones of importance when creating a Temperature Pattern or Profile: Example - Eutectic Reflow Temperature 183 C (Time above 30 – 90 seconds) Board Expansion (90 C) Flux Activation (150 - 160 C) Peak Solder Temperature (221 C+/- 10% A number of Closed Nozzle systems divide these targets into three zones, triggering the profile progress through each zone. In most cases the first zone is a Pre-Heat stage (90 C) which triggers the second zone for flux activation and so on to the last Reflow zone. There is no soaking in this method and prevents the Under Board Heater being used in conjunction with the Top Heater. Running both Heaters from the start of the Heat Cycle is a far better way of reducing the Delta T. The method also prevents the flexibility that is seen in a Multiple Zone Convection Reflow Oven and an APE Rework machine, both of which allow for RAMP SOAK profiling not just Temperature Ramping in three zones. A typical APE profile is 7 -8 zones or segments to accomplish a Pattern or Profile.

Creating a Temperature Profile n n n Profiling “Real Time” or “On The Fly: ” This coined phrase is interesting as Zone Profiling has difficulty in achieving it. When dragging a Temperature Bar to enable solder temperature to reach the air zone temperature, it is characteristic of the software that only the target temperature bar is lengthened – it does not enable the programmer to track the temperature waypoints prior to the change. Thus it is not an accurate “On The Fly” method. With APE software and Multiple Segment Programming, tracking the temperature way-points is possible and an accurate Profile can be created in Real Time. Note: Having the ability to profile “On the Fly” is no substitute for an analytical study of a profile behavior and introducing that study to a new Profile-Pattern starting from an ambient temperature. When selecting the APE “Real Time” feature in the graphical view, the segment of Time and Soak is simply put on “HOLD, ” until the solder temperature achieves the target. The segment is then released and the “HOLD” process repeated through the segments until the Peak Solder Temperature is achieved. The Programmer then simply retraces the Time and Temperature segments selected in the Real Time profile noting the changed intervals and adjusting the original pattern segments and uploading these values to create the new recipe on the Sniper On-Board-Computer. The method is the same for Eutectic or Lead-Free Temperatures Profiles.

Typical Eutectic Profile

Open Versus Closed Nozzle n n n Convection Rework machines either use a Closed Nozzle or an Open Nozzle principle, which APE refers to as an “Open Oven Nozzle. ” The Closed Nozzle design evolved from the early introduction of SMD QFP components where focused heat was mistakenly thought to be the key element in rework, reflowing the leads only to avoid heating the component body and die. With the advent of BGA’s this was not possible and the nozzles were modified to heat the entire component not just the leads, but the Closed Nozzle concept remained. This was acceptable as long as components were large and there was sufficient room around each component to accept a nozzle that would completely enclose and seal the component being reworked. Because these Closed Nozzle systems Place and Reflow in one position the heaters were mounted in a confined space consequentially reducing the air volume and necessitating an adjustable higher air velocity. Twenty years have passed and three important factors now make this design impractical and redundant: 1. Heater Power increased from a typical 800 Watts to >1200 watts to cope with Lead Free solder. 2. Components reduced in size and 3. Components became tightly packed around each other. The Closed Nozzles higher velocity can disturb the subject. With tightly packed components the nozzle can no longer seal the component. The air temperature is hotter and can scorch, it also increases the Delta T in the PCB so that Under Board heating is critical. With an APE Open Oven Nozzle design all these disadvantages are eliminated – AND – in conclusion Closed Nozzles are now sometimes used in a similar way to Open Nozzles BUT the Higher Velocity and Lower Air Volume of the design make it an ineffectual medium that can also disturb adjacent components.

APE Hot Air Convection versus IR Today there are few installations of IR Reflow Ovens used in the assembly of PCB’s within the Electronics Industry ! n

Convection versus IR n n The previous statement should prompt the question as to why? The answer to this question is pertinent as to whether IR is also a suitable method for Reworking, having agreed that a RAMP SOAK method of convection reflow is preferred by an OEM in manufacture. n An IR BEAM is not a LASER! n An obvious statement? Not so – many engineers are confused by the two light technologies and confuse IR with a laser. n Lasers are straight line beams. IR is like a torch light – the further the distance off – the wider the beam – therefore the distance from Target is so critical that it’s rarely repeatable. n IR targets the component or the leads – not the surrounding air – the Temperature Delta must therefore be much wider than a Hot Air Convection Method. n The IR sensor is not in the centre of the beam – where is it? – It’s difficult to calculate and will change with distance off. n IR is sensitive to component coloring – this statement is as true now as it has always been. n The sensor can only visually target the outside lead of a BGA and it must be focused. Camera and Sensor on the lead – with a CSP this is difficult and of course it’s impossible to focus on a centre sphere.

Lead-Free Rework n All APE Rework machines having an APE bottom heater are suitable for Lead-Free rework tasks and are therefore Lead-Free compliant. But – only a Vision-Rework machine is suitable for BGA and CSP components due to limited surface tension characteristics with Lead-Free materials. n Detailed below is a typical Lead-Free material: n Reflow Temperature 221 C Time above Reflow Temperature 60 – 120 seconds n n n Board Expansion (90 C) Unchanged. Flux Activation (150 - 160 C) Unchanged. Peak Solder Temperature (242 - 245 C) The air temperature must obviously be run hotter to reflow, however by raising the bottom heater and having an APE open nozzle design the top reflow temperature can be kept below that which might otherwise be harmful by a variance in Delta T and degradation or catastrophic damage to adjacent components. Notice also that the time above Reflow Temperature is significantly longer than eutectic.

Typical APE Rework Lead Free Process This is an example of a lead free reflow process in use at a Cellular OEM

Typical APE Rework Lead-Free Process Parameters: n n n n Solder characteristics: (formulation confidential) Solder melt: 430 F (221 C) Peak solder temp requirement: 468 F to 473 F (242 C to 245 C) Time above 430 F: 60 seconds minimum. ***Notice: Considerably higher reflow temperature +69 F (21 C) deg over SN 63/37 Time requirement above reflow temperature is longer than typical. Typically 45 -90 seconds, now 60 – 120 seconds Component Characteristics: 14 mm u. BGA, 282 count, 18 mil pitch Max Temperature 482 F (250 C) Max Ramp Rate 4. 5 F/ sec (2. 5 C/sec) ***Notice: Even smaller pitch for this part <. 5 mm Component mass is such that solder temperature can be considered as an accurate scale of component core temperature.

Typical APE Rework Lead-Free Process n n n n PCB Description: Small high-density test board with multiple BGA and CSP devices and high count plastic connectors. 5” x 5” area, 3 mm Thickness, 7 Layers with one full ground plane and 108 grams in weight as an assembly. Machine used: A. P. E. South - Sniper I with R 0028 A Controllers Reflow Controller Profile: SV=560 F (293 C) Ramp: 1: 30 (Time) Adder function OFF Total run time: 2: 45 Preheat Controller Profile: SV=410 F (210 C) Ramp: 1: 30 ***Notice: Higher set points for both bottom and topside heaters than we are typically used to, such as top 450 F (232 C), bottom 325 F (163 C), now 560 F (293 C) and 410 F (210 C) respectively in this example. . Results: See graph. n n Peak Solder Temp 472 F (244 C) Time above 430 F (221 C) 1: 21 Ramp rate at solder/component body 3. 9 F/sec (2. 2 C/sec)

Section Through Lead-Free Process

Sample APE Clients include: Memory Manufacturers: Communications: n Kingston Technology Corsair Memory Simple. Tech ATP Systems PNY Technologies PDP Systems PC Partner Motorola Samsung Kyocera Qualcom Nokia Siemens Nortel n Contractors: Computers & Components Solectron Celestica Jabal Circuits Intel IBM Nvidea n n n n n Security/Defense: US Naval Weapons US Home Land Security US Army NSA FBI Lockheed Harris

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