Automated RF Shield Pad Dressing for PCB Rework
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing method of dressing RF-shield pads on semiconductor printed circuit boards is unreliable, time-consuming, and expensive due to incomplete solder removal, residue solder causing uneven surfaces and potential component damage, and gaps in the seal between the RF shield and pad, which can expose RF-sensitive components to RF signals.
Innovation Solution
An automated tool that pre-heats the PCB to a controlled temperature to melt solder, then uses a moveable desoldering tool to vacuum or electromagnetically remove the solder, ensuring efficient residue removal and applying solder paste for reattachment, thereby reducing thermal stress and improving seal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual dressing with hot tip is used, then solder can be melted and removed, but components can be damaged by the hot tip and residue solder remains on the pad
Solution Approach 1:
The patent segments the dressing operation into two distinct functions: a heating element that melts solder and a separate vacuum nozzle that removes melted solder. This segmentation allows the heating function to be applied broadly to melt solder without concentrating excessive heat at a single point that could damage components, while the vacuum function precisely removes only the melted solder residue.
Solution Approach 2:
The patent introduces melted solder as an intermediary state between the solid solder and removed residue. By heating the pad to melt the solder and then vacuuming the liquid melted solder, the system creates a transitional state that facilitates complete removal without direct contact between the tool and solid solder, preventing damage to adjacent components.
2Productivity
If residue solder is left on the pad, then the dressing process is faster, but the seal between RF shield and pad has gaps exposing components to RF signals
Solution Approach 1:
The patent maintains continuous vacuum action throughout the entire solder melting and removal process. The vacuum nozzle remains engaged with the pad while the heating element melts the solder, ensuring that as soon as solder melts it is immediately removed. This continuous action prevents any residue from remaining on the pad, ensuring complete seal integrity without requiring additional post-dressing steps.
3Productivity
If hot tip is applied directly to solder, then solder melts quickly, but adjacent components can be inadvertently damaged
Solution Approach 1:
The patent extracts the harmful thermal concentration effect by separating the heating function from the removal function. Instead of using a concentrated hot tip that contacts solder directly, the system applies heat more broadly to melt the solder while a separate vacuum system removes the melted material. This extraction of the removal function eliminates the need for concentrated heat application, preventing thermal damage to adjacent components.
4Productivity
If automated dressing is implemented, then throughput increases, but process complexity increases
Solution Approach 1:
The patent merges the heating and vacuum removal functions into a single integrated dressing tool that can perform both operations simultaneously or sequentially. This merging allows the system to achieve automated high-speed dressing by coordinating melt and remove actions in one unified process, rather than requiring separate stations for each function, thereby managing complexity while maintaining high throughput.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The automated system efficiently removes residue solder, reduces the risk of component damage, and ensures a reliable, high-integrity seal between the RF shield and pad, increasing throughput and efficiency in the rework process.
Implementation Method 1
pre-heating a surface of the PCB to a surface temperature (TS) sufficient to heat the solder path and also to prevent thermal stress of the PCB during the dressing process
Implementation Method 2
melting the solder on the solder path
Implementation Method 3
The temperature TN is automatically maintained in the range 200° C. to 250° C. while the melted solder is removed
Implementation Method 4
The melted solder is removed in any manner, such as by vacuuming the melted solder
Implementation Method 5
electromagnetically attracting the melted solder
Data Source
AI summary
A radio-frequency (RF) shield pad is “dressed” by automatically removing melted solder from the shield pad by traversing a pattern of the shield pad. After an RF shield has been removed from a shield pad of a printed circuit board (PCB), the PCB is pre-heated to a temperature sufficient to heat solder on the shield pad and to prevent thermally stressing the PCB during the dressing process. The solder is melted, such as by a heated tip of a desoldering tool, and the melted solder is vacuumed while the tip automatically traverses the pattern of the shield pad, until all or a threshold amount of the melted solder has been removed from the shield pad. After the PCB has been reworked, solder paste is automatically disposed on the RF-shield pad, the RF shield is temporarily mounted on the RF-shield pad, and the PCB is processed in a reflow oven, thereby securely attaching the RF shield to the PCB.