Today’s demanding rework applications, including reballing BGAs, require reliable solutions that directly address the specific challenges involved with each type of rework process. This article provides an overview of the tools and steps you need to reball components cost-effectively and reliably.
Scrapping boards and components can greatly impact the profitability of any job—and should be avoided whenever possible. Therefore, many companies require a quality rework or component reball solution with reliability and repeatability. Applications in the military, medical, aviation, aerospace and networking sectors commonly require this type of component rework.
Various environments—from start-ups to original equipment manufacturers, contract manufacturers, and repair services—frequently seek an economical way to reball Ball Grid Array (BGA) components. Many need the capability to safely heat very large server type printed circuit boards (PCBs) to support the removal or replacement process of surface mount devices (SMDs) without sacrificing quality.
The industry has seen a significant increase in the number of requests to reball BGA packages, enabling components to be used again. There are many reasons to reball a component:
- A replacement may be difficult to find, obsolete or simply unavailable. Often the component is valuable and costly to replace.
- Quick turnaround is critical.
- Leaded or lead-free components are required. As is often the case with military applications, only lead-free components are available and specifications call for leaded components. When this is the case, the lead-free balls need to be removed with heat and vacuum so the pads aren’t damaged, and replaced with leaded balls. Another scenario involves leaded ball BGAs that were shelved when RoHS (The Restriction of Hazardous Substances Directive) standards took effect in 2006. Here, BGA reballing is a great alternative to scrapping, since they can be easily reballed with lead-free balls. Both of these practices are common and widely accepted today.
BGA Reballing Methods
Various BGA reballing kits are available commercially that utilize different methods to rework the component. Some come in a “preform” with the proper size ball, pitch, and ball pattern, which is manually aligned to the BGA. This method of reballing BGAs can be quite expensive and is not very flexible. Other kits match up a frame and mask to the BGA and use solder balls purchased in bulk containers. This method is more economical and more flexible, however another cost factor comes into play in the reflow step.
Reflowing Reballed BGAs
A critical cost factor in reballing BGAs is how they are reflowed. There are two widely used solutions for reflowing solder balls―ovens and rework systems. Using a reflow oven requires shutting down the SMT line to run the BGAs through. This is not a cost-effective solution. In fact, you may even lose money since production is halted. When you use a BGA rework system to reball components, you inflict the same damage to your bottom line. Instead of using the rework system for the tasks it was purchased for—removal or placement of components—you are tying it up for reballing.
The Mini-Oven: A Cost Effective Way to Reball BGAs
A mini oven is very cost-effective alternative to large ovens and rework systems to reflow reballed BGAs. The Martin Mini-Oven is a small, intuitive, stand-alone bench top convection reflow oven that is simple to use and programmable to comply with today’s standards.
So how does a small bench top unit handle the task? The unit is powered by IR lamps and reflectors to produce a heat source focused on the part. An optimized component heating process is the result of the combination of IR-radiation and convection technology, providing efficient temperature distribution with a powerful 500W IR-bottom heater. Process gas can be used to minimize unwanted oxidation.
The Mini-Oven frame, mask and holder are used in the reballing process. The frame is inserted into the holder, the component added, flux applied and the mask aligned. Masks can be modified to accommodate different sizes by using Kapton® tape to define the array. Or, for more difficult arrays, custom masks can be made to match the ball pattern. The solder balls are distributed on the mask, filling the openings. Any vacancies can be filled by brushing. Excess balls are discarded, or collected depending on operator choice. The unit is placed in the Mini-Oven, a program selected and the unit started. Through a porthole, the progress can be observed with or without a microscope as needed. At the end of the cooling process, the component can then be removed and inspected.
With the ability to store and edit up to 25 profiles, operators can save trial and error efforts. Adjustable hold time, temperature offset, and temperature damping provide process stability. Simple, safe rapid technology soldering profiles rigorously apply settings within the permitted thermal limits, heat at the highest advisable thermal ramp rates and maintain within a safe temperature zone. The result is a reballing process in as little as three minutes.
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