JP4284163B2 - Thin board fixing method - Google Patents

Description

  The present invention relates to a method for mounting and fixing a thin flexible printed wiring board.

Recently, printed wiring boards have been used in many electronic devices due to improved productivity and high reliability. In recent years, flexible printed wiring boards (hereinafter referred to as FPC) having a conductor pattern on the surface of a film-like insulating substrate are frequently used in order to cope with the reduction in size and weight of electronic devices. In this FPC, a so-called surface mounting method in which an electronic component is mounted on the surface of the conductor pattern is widely adopted.
FPCs usually go through a cream solder application process, etc., depending on the placement position of the electronic components to be mounted, etc., then mount the electronic components on this cream solder application part, and then heat them to melt the cream solder The electronic component is cured and bonded to the FPC (see Patent Document 1).

  Because FPC is flexible, and due to recent progress in miniaturization, it is complicated and unstable to handle each of the above processes and storage / transfer individually. It has been practiced to form a weak adhesive pattern on the surface of a plate material (plate) having, and to attach and fix an FPC to the weak adhesive pattern (see Patent Document 2).

As shown in FIG. 3, the holding and conveying jig 20 of Patent Document 2 protrudes from the surface of the plate 21 to form a weak adhesive pattern 23 using a weak adhesive 22 made of, for example, a silicone resin. in which the weak-stick adhesive pattern 23, FPC or formed at a position corresponding to the non-conductive portion of the FP C the laminated conductive material for producing clad plate (both not shown), electrons FPC It is not formed at the position 24 corresponding to the conduction part on which the component is mounted.
In another aspect, after a weak adhesive pattern is formed on a portion corresponding to FPC or the like, an adhesive force is not provided at a position corresponding to a conductive portion on which an electronic component is mounted on the surface of the weak adhesive layer. The thing which does not have this is also disclosed.
In the formed weak adhesive pattern 23, a recess 25 is formed in a required portion so that a protrusion provided on the back surface of the FPC (the surface opposite to the surface on which the electronic component is mounted) can be received. Is provided.
JP-A 63-204695 Japanese Patent No. 3435157

This type of FPC fixing jig is used many times by repeatedly bonding and peeling FPC on the surface of the weak adhesive layer.
If the adhesive strength of the weak pressure-sensitive adhesive layer that bonds and fixes the FPC is too weak, the FPC may not be able to be fixed and held over the required time and period. in FPC low rigidity as, mosquitoes Lumpur occurs in FP C during peeling after component mounting, hindered the subsequent mounting and fixed the thin substrate to the portable electronic devices such as various types of electronic devices It becomes easy.

Moreover, depending on the shape of the FPC, particularly in a thin substrate having a narrow pattern, if the adhesive layer has a strong adhesive force, it may be peeled off from a fixing jig after mounting an electronic component such as a flip chip. The problem that the FPC tears easily occurs.
Furthermore, in a thin substrate with high rigidity such as a double-sided FPC or a multilayer FPC, the thin substrate is warped due to the difference in linear expansion coefficient between various members constituting the FPC due to heating in the reflow furnace. There may be a problem of peeling off due to warm air.
In addition, the metal mask used in the printing / coating process of cream solder on the FPC mounted and fixed on the fixing jig is adhesively fixed to the weak adhesive layer exposed outside the part that fixes the thin substrate, and the metal mask There was also a tendency to impair the operability of.
Therefore, in order to solve these problems, the present invention provides a fixing method using a versatile thin substrate fixing jig that does not require the formation of an adhesive layer with controlled peel strength for each thin substrate to be processed. This is the issue.

The FPC fixing method using the thin substrate fixing jig of the present invention is a thin substrate fixing method using a thin substrate fixing jig used when mounting a thin substrate component having an adhesive layer on one side of a flat plate, during fixing, by superimposing at least an opening is formed in the portion facing the component mounting portion of the thin substrate (membrane) cover film, characterized in that fixed to the weak adhesive layer with a thin substrate.

According to the thin substrate fixing method of the present invention, by using the (thin film) cover film that covers almost the entire surface of the thin substrate fixing jig, the area where the (thin film) cover film contacts the weak adhesive layer is increased. it can even adhesion of the low adhesive layer is small fence, it is possible to sufficiently secure the bonding strength of (thin) cover film, and, by covering the periphery of the thin substrate (thin film) cover film, Even if the holding / fixing force to the thin substrate held / fixed on the thin substrate fixing jig can be sufficiently ensured even if the adhesive force of the weak adhesive layer is reduced, an effect can be achieved.
In addition, there is a problem that the metal mask used in the printing / coating process of cream solder on the FPC is adhesively fixed to the weak adhesive layer exposed except for the portion fixing the thin substrate, and the operability of the metal mask is impaired ( The thin film) cover film covers the periphery of the thin substrate, which can be solved by dramatically reducing the exposed portion of the weak adhesive layer.

The present invention secures a sufficient adhesive force to the cover film by increasing the contact area with the weak pressure-sensitive adhesive layer even if the adhesive force per unit area is reduced, and also has a sufficient adhesive force Basically, the adhesive force which is insufficient depending only on the adhesion area of the thin substrate to the thin substrate fixing jig with the weak pressure-sensitive adhesive layer is compensated by covering a part of the thin substrate.
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory plan view showing a state in which the (thin film) cover film of the present invention is applied and an FPC is bonded and held on a thin substrate fixing jig.
FIG. 2 is a cross-sectional explanatory view taken along line XX of FIG. Note that FIG. 2 includes a plurality of flip chips that are not shown in FIG. 1 and are surface-mounted on a thin substrate.

1 and 2, the thin substrate fixing jig 1 is configured such that after the FPC 4 is placed on the surface of the weak adhesive layer 3 formed on almost the entire surface of one side of the flat plate 2, the required portion of the FPC 4 is moved from above. In the state of being covered, the (thin film) cover film 5 covers almost the entire surface of the thin substrate fixing jig 1.
On the (thin film) cover film 5, a mounting position 7 (indicated by a one-dot chain line) on which the flip chip 6 to be mounted on the surface of the FPC 4 is mounted / adapted is cut off. , Uniformly extended.
In the weak pressure-sensitive adhesive layer 3, if there is a protruding portion 8 provided on the back surface of the FPC 4 (the surface opposite to the surface on which the electronic component is mounted), the missing portion 9 is provided in the required portion so that it can be received. Or a recess may be provided.

The weak pressure-sensitive adhesive layer 3 is formed as a weak pressure-sensitive adhesive layer pattern according to the shape of the FPC 4 so as to be convenient for positioning and mounting the FPC 4 on the thin substrate fixing jig 1, and the weak pressure-sensitive adhesive layer pattern. It is also possible to form a weak pressure-sensitive adhesive layer that adheres the cover film 5 (thin film) slightly apart.
Further, it may be possible to adopt a mode in which a through hole is provided in a flat plate at a position corresponding to a position where a flip chip (electronic component) is mounted on a thin substrate.
The surface of the weak pressure-sensitive adhesive layer 3 is preferably finished to a mirror surface in order to improve self-adhesion.
The thin substrate bonded and fixed to the thin substrate fixing jig of the present invention configured as described above is used for storage and transfer, and printing such as cream solder for surface mounting of electronic components on the thin substrate It is used for various measures such as melting, solidifying and bonding cream solder.

The material of the flat plate 2 is not particularly limited as long as it is a rigid body having heat resistance capable of withstanding heating for flip chip mounting by cream solder. For example, aluminum alloy, glass epoxy composite plate, magnesium alloy, etc. Are mentioned as preferred.
The material for forming the weak pressure-sensitive adhesive layer is preferably one having heat resistance, cold resistance, electrical insulation, self-adhesion, and capable of repeatedly adhering, for example, silicone, polyimide silicone, Examples thereof include elastomer materials having high heat resistance such as those obtained by curing a fluorinated elastomer having a fluorinated polyether skeleton having a curable functional group.

Although the thickness of the weak pressure-sensitive adhesive layer can be determined as appropriate, when the thickness is sufficient to correspond to the protrusion on the back surface of the flip chip, Processing steps requiring skill such as counterboring can be simplified.
(Thin film) The cover film 5 is preferably made of a thin film and has high heat resistance capable of withstanding heat treatment for melting and solidifying cream solder for mounting a flip chip. From these points, a metal foil such as aluminum, copper, or iron is desirable and has a thickness of about 10 μm to 100 μm. Moreover, it is also possible to employ | adopt resin films with high heat resistance, such as a polyimide, polyamide, and polyetherimide. The thickness at this time is preferably about 10 μm to 100 μm.

Primer treatment is applied to one side of an aluminum plate having an outer shape of 150 mm × 150 mm and a thickness of 1.5 mm, and a liquid silicone: KE-1800 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) is used with a thickness of 0.04 mm using a screen printing method. The entire surface of the pressure-sensitive adhesive layer was applied to produce a base for a thin substrate fixing jig.
Separately, hole processing was performed on a position facing the FPC component mounting portion on a 0.05 mm thick polyimide film to prepare a cover film.
An FPC was placed at a required position on the base of the thin substrate fixing jig, and a cover film was overlaid thereon.

This fixing jig was subjected to a cream solder printing process using a metal mask. It was confirmed that the FPC was not taken on the metal mask, and the metal mask was not stuck on the adhesive layer and was difficult to remove, so that it could be processed without problems.
Furthermore, even if it is subjected to a component (flip chip) mounting process and a solder reflow process, the FPC is not displaced or peeled off, and also when the FPC after component mounting is peeled from the weak adhesive layer, It was confirmed that each process can be carried out smoothly without problems such as curling and tearing.

  According to the present invention, the adhesive force of the weak pressure-sensitive adhesive layer can be further reduced, and the FPC curling and tearing that are likely to occur at the time of peeling during operation of the FPC and peeling from the thin substrate fixing jig can be avoided, and By avoiding the problem of the operability of the metal mask, an excellent effect can be achieved as a thin substrate fixing method which is very desirable in the field of electronic equipment manufacturing.

It is a plane explanatory view showing the state where FPC was bonded and held to a thin substrate fixing jig by applying the (thin film) cover film of the present invention. It is sectional explanatory drawing in alignment with the XX line of FIG. 1 including flip chip mounting. It is explanatory drawing which shows the conventional holding | maintenance carrying jig | tool, (A) is a top view, (B) is a fragmentary sectional view along the XX line of (A).

Explanation of symbols

1: Thin substrate fixing jig 2: Flat plate 3: Weak adhesive layer 4: FPC
5: (Thin film) Cover film 6: Flip chip 7: (Flip chip is placed / adapted) Mounting position 8: Projection 9 (on the back of the FPC) 9: Defect 20 (of weak adhesive layer): Holding transport Jig 21: Plate 22: Weakly adhesive 23: Weakly adhesive pattern 24: Position corresponding to a conduction part (where an electronic component is mounted on the FPC) 25: Recess

Claims (1)

A thin substrate fixing method using a thin substrate fixing jig used when mounting a thin substrate component having a weak adhesive layer on one side of a flat plate, and at least facing the component mounting portion of the thin substrate when fixing the thin substrate and superimposed to form an opening in a portion (the thin film) cover film, the thin substrate fixing method which is characterized in that fixed at the weak adhesive layer with a thin substrate.

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