Underfilled components are used in consumer electronic products (mobile devices, portable computers etc.), in the automotive industry (sensor modules, engine control units etc.) or whenever flip chips are incorporated in products with maximum miniaturization.
An underfilled chip contributes to an improved overall product quality, offering higher reliability and better lifetime. The underfill material provides protection against humidity, thermal stress and all kinds of mechanical impact.
Reworking components with rework-able underfill is applicable if the components or substrates are expensive, hard to obtain or if complete products need to be saved.
What are the challenges?
- Avoid disturbance of neighboured components on small-sized (pitch down to 400 µm or below) high-density SMD assemblies with distance down to 300 µm
- Process fluctuations during production result in undefined fillet shapes
- Avoid thermal and mechanical stress to the surface top metal layer and solder resist
- Find the appropriate process according to the specific underfill material
- Variable stack heights require adaptive tooling and specialized rework equipment
The Finetech Solution
Various Underfill Materials
The appropriate rework process is mainly determined by the underfill material. There are various expoxy based underfill materials differing in the composition and characteristics:
- Hard or flexible
- Expansion ability
- Curing temperature
- Removal temperature
- Purely mechanical or chemical underfill removal
Typical Underfill Rework Process
The whole rework process consists of the following steps:
- Preprocessing of the component, if necessary (cut underfill to avoid lifting neighboured components)
- Desoldering using a clamping tool
- Solder removal
- Residual underfill removal using heat, brush and chemical solvent
- Soldering of new component
- Underfilling and curing
Highly precise clamping tool with vacuum support for secure handling
- Designed to compensate thermal expansion effects
- Provides very localized top heat input to avoid disturbance of neighboured components
- Inert gas support provides process atmosphere adequate to reflow oven conditions
- Tool design allows access to densely assembled components with small clearance
Variable knife for fillet cutting
Q-tip, ESD brush, chemical solvent
Integrated Process Management (IPM)
The Integrated Process Management (IPM) is the center piece of a FINEPLACER® system1 - the place where it all comes together. IPM is more than just thermal management. It synchronizes the control of all process modules and their related parameters:
- Controlled and precisely balanced interaction of top and bottom (pre-)heating and cooling
- Control of temperature, time, force, power, energy, flow
- Controlled process gas integration for reduced solder contamination, minimized surface tension effects and smooth spherical solder residues
IPM is very complex, yet easy to access. Via the GUI of the operating software, the user has perfect control of all required adjustments. Just drag 'n drop to define temperature ramps or activate process modules. All settings are represented in only one profile, making for a very intuitive work flow.
The operating software provides an ever-growing library of profiles for all kinds of processes. It also offers comprehensive data logging functions essential for statistical process control.
In combination with the system-to-system process transfer capability this is as easy as process development can get.
1 FINEPLACER® core offers co-ordinated top and bottom heating but does not support IPM
Recommended Rework Systems
Amongst other factors, the recommended system mainly depends on size and pitch of your component and the required process flexiblity.
Browse our product range or get in contact with your sales contact to figure out the best equipment solution for your needs.