Board-level + Workforce Issues

Technical Needs, Gaps and Solutions

Board-level rework and repair technology issues, the associated needs, technology status of those needs, as well as gaps and challenges to overcome, are summarized below. Workforce needs, gaps, challenges, and solutions are included. The time period considered is from 2024 to 2034.

Technology Status Legend

For each need, the status of today’s technology is indicated by label and color as follows:

In-table color + label key	Description of Technology Status
Solutions not known	Solutions not known at this time
Solutions need optimization	Current solutions need optimization
Solutions deployed or known	Solutions deployed or known today
Not determined	TBD

Table 1. Board-level Rework and Repair Gaps, and Today’s Technology Status with Respect to Current and Future Needs

At the component/socket level, on-going miniaturization and increasing integration of heterogenous elements are key drivers for many of the needs and challenges. At the board level, miniaturization and increasing component diversity are key drivers.

	ROADMAP TIMEFRAME
TECHNOLOGY ISSUE	TODAY (2024)	3 YEARS (2027)	5 YEARS (2029)	10 YEARS (2034)
BOARD-LEVEL ISSUE #1: Issues related to site redressing and adjacent reflow during rework of component on densely populated board
NEEDS	Component handling. Adding solder paste to component board site. Tools required to handle components in tight areas including redressing of board pads sites. Skills training required for working in tight areas.
CURRENT TECHNOLOGY STATUS	Solutions need optimization
	Some equipment is available but needs improvement and refinement.
GAPS	Lack of tools to handle components in tight areas. Some discrete components are virtually touching one another in design which does not confirm to IPC design guidelines.
CHALLENGES	Automated redressing/ solder removal is a challenge with densely populated boards. Solder wick used. Hand soldering equipment to use for this area is a challenge, especially with thicker boards. Skills gap for hand soldering for densely populated boards.
BOARD-LEVEL ISSUE #2: Proliferation of underfill and conformal coatings (removal issues)
NEEDS	Need higher yields for underfilled / conformally coated component rework. Manual method yield could be less than 50% (Lack of process control and repeatability) Rework times are too long so could scrap board. (Military versus consumer rework boards $$$- Can not scrap a high value board). Para-xylylene conformal coating rework is very challenging (Micro-sand blaster is used or expensive Plasma). If Para-xylylene (JB) coating gets under component (such as BTC component) site preparation step is much more difficult. Reworkability Ranking (1 is good, 5 is poor): Acrylic (AR)- 1, Polyurethane (UR)- 3, Epoxy (ER)- 3, Silicone (SR)- 2, Para-xylylene (XY)- 5) (Reference: Chapter 13: Conformal Coating book chapter by Jason Keeping (Wiley Book on Lead-free Soldering Process Development and Reliability))¹
CURRENT TECHNOLOGY STATUS	Solutions need optimization
	Manual removal using makeshift tools, soldering irons with knife blades or cutting tools used to assist in removal of underfill/conformal coating to break bond between underfilled/ conformal component and PCB. Removal of underfill via solder wick and soldering iron. Milling of the component on the board to remove both the component and the underfill/ conformal coating to 4 to 5mils height from the board surface. Then new part is attached during a typical rework process.
GAPS	Need for higher yielding, less labor-intensive (manual) underfill/ conformal coating rework techniques. Conventional computer numerical control (CNC) not developed for this process.
CHALLENGES	Customer prefers non-reworkable underfill versus reworkable underfills based on reliability performance Neither underfill nor conformal coating reflows like solder does. Heat does not help in its removal. When adding heat to underfilled area, solder will melt and move to other areas via pressure of underfill material which is softened. Reworkable underfills are still not very reworkable. Rework times are increased to remove and removal process is not very repeatable. Need skilled operators.
BOARD-LEVEL ISSUE #3: Proliferation of underfill and conformal coating (site cleanup issues)
NEEDS	Need more new chemistries (underfill and conformal coating) with ease of clean-up especially for underfills. Para-xylylene (or equivalent) conformal coating removal methods need to be developed that are more economical. Continued development of nano-coatings for simpler application as well as removal.
		Milling of component or conformal coating/ underfill which will eliminate the need for site cleaning. Transition from manual to site cleaning to milling.
CURRENT TECHNOLOGY STATUS	Solutions need optimization
	Solder wick and soldering tip are used with excess force to remove material which can lead to pad and solder mask damage especially as the pad sizes become smaller (e.g., down to 0.5mm pitch components and below). Increased rework failure rate. Also site cleaning tools are used (heat, vacuum and non-contact site cleaning).
GAPS	Lack of alternative materials. Need to break bond of underfill/ conformal coating material. Use either a knife or soldering iron with a blade used.	Lack of alternative materials. Need to break bond of underfill / conformal coating material. Use either a knife or soldering iron with a blade used. Milling process eliminates the need for heat-based site cleaning
CHALLENGES	Customer prefers non-reworkable underfill versus reworkable underfills Neither underfill nor conformal coating reflows like solder does. Heat does not help in its removal. When adding heat to underfilled area, solder will melt and move to other areas. Reworkable underfills are still not very reworkable. Rework times are increased to remove and removal process is not very repeatability. Need skilled operators.
BOARD-LEVEL ISSUE #4: Proliferation of single piece RF shields (Removal and replacement challenges)
NEEDS	Methods and techniques to easily remove a variety of custom RF shields. All shields are custom in nature. Need methods that will accommodate different shapes, sizes while not disturbing neighboring components and components internal to the shield. Current methods not set up for low volume and prototypes for these devices. Need to avoid adjacent component reflow concerns inside shield especially if underfilled component.
CURRENT TECHNOLOGY STATUS	Solutions not known
	Need for custom tools to remove and replace. Further development needed May need separate specialized workstation/ machine with different attachment points of the nozzle for removal and replacement of shield.
GAPS	Lack of custom tools
CHALLENGES	The soldering “lip” of these shields are right next to components next to the shield or near the shield lip underneath the shield. This causes adjacent component and components inside the shield to reflow. For replacement of larger/heavy RF shields, nozzles may not be able to place the shield accurately (Co-planarity issue).
BOARD-LEVEL ISSUE #5: Increasing density of component on board- rework causing adjacent component to reflow or partially reflow (for BGAs, connectors etc), different board laminates used (Rogers versus FR4), different rework heat sources (laser, etc.)
NEEDS	Reduced adjacent temperatures during rework
CURRENT TECHNOLOGY STATUS	Solutions need optimization
	Increased thermal keep away strategies (different materials/gels used: not just Kapton tape and shields). (Shields are used if necessary) Bake product board to remove moisture from adjacent components which are subject to heat. Laser used for specific applications only
GAPS	Thermal process management control but keep-out areas are getting smaller. Thermal modelling of adjacent components and adjacent temperature sensitive components and board itself during rework to understand and improve design layout. Dependent on type of product being built. Mainly covering military/defense and telecom-high reliability.
CHALLENGES	Design guidelines for spacing of components are not being followed (e.g., consumer product). Need to include design for rework considerations for single site rework in all type of products, especially high reliability. Thermal delivery system of some current equipment for thermal process management control
BOARD-LEVEL ISSUE #6: High thermal mass board rework (Increased rework soak/preheat times)
NEEDS	Other heating technologies (such as vapor phase) for reworking PCBs to be developed. Will be challenging to develop for single rework locations.
CURRENT TECHNOLOGY STATUS	Solutions need optimization
	Hot air or IR systems with bottom side heating limited. Addition of convection/ IR spot heating under board. Hot-plates and edge heating. Stand-alone preheater next to rework machine to pre-heat board to 140C before rework to reduce rework soak/preheat times (Need to be sensitive to temperature sensitive components on the board).
GAP	Reducing rework soldering times
CHALLENGES	Reducing times to conform to component or board or solder temperature and moisture sensitivity level (MSL) requirements and improve process window. Need more robust laminate materials and solder fluxes which will not degrade with longer soldering times and temperature. Do not overheat temperature sensitive components during preheat and rework.
BOARD-LEVEL ISSUE #7: Availability of rework machines which can rework very small components and very large components on the same board.
NEEDS	Rework equipment for both very small component and very large components	Rework equipment for both very small component and very large components: Increased movement to address very large components over very small components during rework. Machine aligned more for larger component rework.
CURRENT TECHNOLOGY STATUS	Solutions need optimization
	IR has an advantage for small components, Convection has more of advantage for larger components (more heat energy and quicker cycle times). Some equipment can do this but flexibility to handle the component range is limited.
GAPS	Lower-end rework equipment may not be able to rework large components. Need higher heating power for larger components. Need smaller heating power for smaller components. Machine dependent.
CHALLENGES	Some machines are set up for small components and some machines are set up for large components. General trend for rework equipment development will be larger component rework.
BOARD-LEVEL ISSUE #8: Mirror image rework
NEEDS	Reduce bottom side thermal issues for bottom side components: Monitor and control bottom side heating. Profile both components (top and bottom side) to develop a lower temperature rework process.
CURRENT TECHNOLOGY STATUS	Solutions not known
GAPS	No industry guideline on what types of component should not be mirror imaged, e.g., do not mirror image BGA with BGA components. Lack of designer education. Increased thermal modelling of mirror imaged components and the board itself during rework to understand and improve design layout.
CHALLENGES	Process control system and machine capabilities to reduce this effect to prevent thermal issues with bottom side component (directly underneath) Mirror-imaged components in board rework causing thermal issues with bottom side components which can reflow or partially reflow (for BGAs, connectors etc), which could cause reliability issues. (Fully reflowed part on the bottom side if a large size BGA is used, which could fall off the board during rework.) Need to include design for rework considerations for mirror imaged components during rework in all type of products.
BOARD-LEVEL ISSUE #9: Mirror image rework X-ray inspection (cost criteria needing computer tomography (CT) inspection)
NEEDS	Develop more cost-effective X-ray platforms for mirror image rework.
		Consider redesign of board so less mirror image BGA rework needed.
CURRENT TECHNOLOGY STATUS	Solutions need optimization
	Expensive X-ray equipment solutions for mirror-image rework. Have to tilt board in X-ray machine. Challenging to interpret solder joint. CT is then used which is expensive and slow.
GAPS	Lack of cost-effective and functional X-ray systems. Require less time for X-ray inspection.
CHALLENGES	High cost for X-ray systems with this capability. Designers are not communicating with manufacturing on the feasibility of rework for mirror-imaged components.
BOARD-LEVEL ISSUE #10: DfM for assembly and rework
NEED	More participation from rework standpoint in design. More robust high temperature materials needed or acceptance of using lower temperature solders or epoxies for rework.
CURRENT TECHNOLOGY STATUS	Solutions need optimization
GAPS	Lack of participation from rework standpoint in design
CHALLENGES	Participation from rework/repair personnel with input into the design meeting (DfR)

Approaches to address Needs, Gaps and Challenges

Table 2 considers approaches to address the above Board-level Rework and Repair needs and challenges. The evolution of these is projected out over a 10-year timeframe using technology readiness levels (TRLs).

In-table color key	Range of Technology Readiness Levels	Description
2	TRL: 1 to 4	Levels involving research
6	TRL: 5 to 7	Levels involving development
9	TRL: 8 to 9	Levels involving deployment

Table 2. Board-level Rework and Repair Potential Solutions

		EXPECTED TRL LEVEL*
TECHNOLOGY ISSUE	POTENTIAL SOLUTIONS	TODAY (2024)	3 YEARS (2027)	5 YEARS (2029)	10 YEARS (2034)
Board-Level Issue # 1: Issues related to site redressing and adjacent reflow during rework of component on densely populated board	Component handling.	8	8	8	8
	Challenges of adding solder paste to component board site.	6	8	8	8
	Automated Tools required to handle components in tight areas	8	8	8	8
	Automated Redressing Tools on board pad site.	6	8	8	8
Board-Level Issue # 2: Proliferation of underfill and conformal coatings (removal issues)	Manual Removal of conformal coating (Acrylic (AR) )	8	8	8	8
	Manual Removal of conformal coating (Para-xylylene (XY) )	5	7	8	9
Board-Level Issue # 3: Proliferation of underfill and conformal coating (site cleanup issues)	Board Site cleanup of conformal coating (Acrylic (AR) )	8	8	8	8
	Board Site cleanup of conformal coating (Para-xylylene (XY) )	5	7	8	9
Board-Level Issue # 4: Proliferation of single piece RF shields (Removal and replacement challenges)	Preventing adjacent component issues during shield removal	3	5	6	7
	Preventing adjacent component issues under shield during shield removal	3	5	6	7
Board-Level Issue # 5: Increasing density of component on board- rework causing adjacent component to reflow or partially reflow (for BGAs, connectors etc), different board laminates used (Rogers versus FR4), different rework heat sources (Lazer etc)	Reduced adjacent device temperatures during rework	6	6	7	8
	Thermal modelling on the design level	1	1	2	2
Board-Level Issue #6: High thermal mass board rework (Increased rework soak/preheat times)	Convection/ IR spot heating under board	8	8	9	9
	Edge heating into board	6	7	8	9
	Stand alone or integrated preheater into rework process	8	9	9	9
Board-Level Issue # 7: Availability of rework machines which can rework very small components and very large components on the same board	Lower air flow in convection for smaller parts to prevent part movement	8	8	9	9
	IR development for very large parts with targeted/ confined thermal heating to prevent adjacent reflow	6	7	8	9
	Placement of small components (Vision system imaging, pick up nozzles)	6	7	8	9
	Placement of large components (Vision system imaging, pick up vacuum pressure/mechanical removal force)	5	6	7	8
	Automation of rework processes (alignment, paste dispense, board registration)	4	5	6	7
	Specialized hands on BGA/ BTC training	4	5	6	7
Board-Level Issue #8: Mirror image rework	Ensure Top and bottom side mirror imaged components fully reflow even if top and bottom side components are partially mirrored	2	4	6	8
	Development of design software to understand the risks associated with mirror image component rework	1	1	3	5
	Incorporate into Design guideline rules on rework of mirror images components (what is feasible and what is not)	4	6	7	8
	Improved Thermal delivery system of equipment for thermal process management control	3	5	7	8
Board-Level Issue #9: Mirror image rework X-ray inspection (cost criteria needing CT inspection)	CT development at low cost and reduced time for inspection	5	6	7	8
	DT (Digital Tomosynthesis) at low cost and reduced time for inspection	6	7	7	8
Board-Level Issue #10: DfM for assembly and rework	More participation from rework standpoint in DfM	3	4	4	4
Board-Level Issue #10: DfM for assembly and rework	DfM software analysis tools with considerations incorporating rework	5	5	5	5

Workforce

Finally, in Table 3, consider overarching workforce needs, as follows:

Table 3. Workforce Gaps, and Today’s Technology Status with Respect to Current and Future Needs

	ROADMAP TIMEFRAME
TECHNOLOGY ISSUE	TODAY (2024)	3 YEARS (2027)	5 YEARS (2029)	10 YEARS (2034)
WORKFORCE ISSUE #1: Lack of rework specialists/ ageing workforce- lack of engineers to do rework process development
NEED	Training programs for rework specialists. More automation for rework processes as less engineers. (Fully automated rework is the long-term goal.)
CURRENT TECHNOLOGY STATUS	Solutions need optimization
	Lack of specialized training (hands-on with experience). Lots of training requests for equipment based on new employees and employee turnover. Push for more automation in rework processes such as component alignment.
GAPS	Lack of curriculum courses with hands on rework demonstrations. (IPC 7711.21: does not give information on board density for rework, chemistry used, materials, etc., just talks about the method.) Online train-the-trainer modules. Lack of automation in rework processes such as component alignment.
CHALLENGES	Rework is more of an art to understand for specialized training, but we don’t have enough trained specialists to transfer knowledge.

Table 4 considers approaches to address the above Workforce needs and challenges. The evolution of these is projected out over a 10-year timeframe using technology readiness levels (TRLs).

In-table color key	Range of Technology Readiness Levels	Description
2	TRL: 1 to 4	Levels involving research
6	TRL: 5 to 7	Levels involving development
9	TRL: 8 to 9	Levels involving deployment

Table 4. Workforce Potential Solutions

EXPECTED TRL LEVEL*

TECHNOLOGY ISSUE

POTENTIAL SOLUTIONS

TODAY

(2024)

3
YEARS

(2027)

5
YEARS

(2029)

10
YEARS (2034)

Workforce Issue #1: Lack of rework specialists/ ageing workforce- lack of engineers to do rework process development

Development of training programs for BGA/ BTC rework (in-class and online)

5

6

7

Board Assembly Acronyms

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